Subaru Legacy/Outback

1999-2003 of release

Repair and operation of the car


Subaru of Legasi, Autbek
+ Cars Subaru Legacy, Outback
+ Operation manual
+ Routine maintenance
+ Engine
+ Cooling systems, heating
- Power supply system and release
   Specifications
   + System of injection of fuel
   - Control systems of the engine and decrease in toxicity of the fulfilled gases
      ESM - check of serviceability of a state and replacement
      Diagnostics of malfunctions - the general information and preliminary checks
      System of onboard self-diagnostics (OBD) - the general information
      Application of an oscillograph for supervision of working parameters of a control system
      Removal and installation of components of systems of decrease in toxicity of the fulfilled gases
   + System of production of the fulfilled gases
+ Electric equipment of the engine
+ Manual box and differential
+ Automatic transmission
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment



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System of onboard self-diagnostics (OBD) - the general information

 On the models equipped with OBD II system on established under a cowl Schild there has to be a record "OBD II compliant", and the diagnostic DLC socket has to be 16-contact. As a rule, the OBD II system surely equips the models intended for the North American market since 1996 vyp., and also the European models, since 2000 vyp.


General description of OBD system

Problem of any onboard system of self-diagnostics (OBD) is identification of refusals and violations of functioning of under control systems with entering in memory of the processor of the corresponding diagnostic codes (DTC) and the notification of the driver about the violation fact (usually by means of the control lamp of refusals of MIL/" which is built in in a combination of devices check the engine").

Besides the DTC code in memory of ECM it is fixed also current working parameters of the engine at the time of violation identification.

At violation of serviceability of functioning of the information sensors which are taking part in process of management of the engine, ECM can make switching of systems in emergency operation. Thus the basic working parameters ensuring adequate functioning of the engine (some absolute pseudo-signal of the faulty sensor is feigned directly by the module of management), however with inevitable decrease in efficiency of its return and increase in an expense of a topilv are activated, - the car should be driven away on car repair shop for the purpose of identification and elimination of causes of failure.

Some diagnostic devices making monitoring of separate parameters of systems of decrease in toxicity and fixing the revealed refusals in memory of the onboard processor in the form of individual codes of malfunctions are a part of OBD system. The system makes also check of sensors and actuation mechanisms, controls operational cycles of the vehicle, provides possibility of freezing of parameters and cleaning of the block of memory.

The models considered in the present manual can be completed as system of onboard diagnostics of the second generation of the SAE standard (OBD II), and firm OBD system of the Subaru standard (some of l models 2.0 and 2.5). A basic element of any OBD system is the onboard processor more often called by the electronic module of management (ECM). ECM is a brain of a control system of the engine. Basic data arrive on the module from various information sensors and other electronic components (switches, the relay, etc.), and also signals of the registered OBD of refusals and violations. Codes of the registered malfunctions are fixed in memory of the processor.

Data read-out of memory of the OBD processor is made by means of the special scanner (the SAE standard - GST or Subaru - SSM) connected to the 16-contact diagnostic socket of reading of a database (DLC) located under the dashboard from the driver's party of the car.

 Reading of the DTC codes on models with OBD II is possible with the help as GST, and SSM, on models with OBD Subaru - only by means of the SSM monitor.


On service of components of control systems of engine/decrease in toxicity of the fulfilled gases special guarantee certificates with the extended validity extend. It is not necessary to make attempts of independent performance of problem diagnostics of ECM or replacement of components of system, to an exit of terms of these obligations, - address to specialists of firm car repair shops of the Subaru company.

Data on diagnostic units

Check of serviceability of functioning of components of control systems of the engine and decrease in toxicity of the fulfilled gases can be made by means of the universal digital measuring instrument (multimeter). Use of the digital measuring instrument preferably for several reasons. First, on analog devices it is rather difficult (sometimes, it is impossible), to define result of the indication to within the 100-th and thousand shares while at inspection of the contours including electronic components in the structure, such accuracy is of particular importance. The second, not less important, that fact is the reason that the internal contour of a digital multimeter, has rather high impedance (internal resistance of the device makes 10 million Ohms). As the voltmeter is connected to the checked chain in parallel, the accuracy of measurement of subjects is higher, than smaller parasitic current will pass through actually device. This factor is not essential at measurement of rather high values of tension (9 ÷ 12 V), however becomes defining at diagnostics of the elements which are giving out low-voltage signals, such as, for example, a lambda probe where it is about measurement of shares of volt.


Parallel supervision of parameters of signals, resistance and tension in all chains of management is possible by means of the splitter included consistently in the socket of the module of management (ECM). Measurement of parameters of signals on splitter plugs in various modes of functioning of the engine allows to define current state of the last and to reveal the violations taking place.

At diagnostics of electronic control systems of the engine, transmission, ABS and SRS special scanners of the SAE (GST) standard, - OBD II, - or the firm Subaru Select Monitor (SSM) scanner, - Subaru standard OBD are used. Many SAE scanners of the second generation (OBD II) are multipurpose, at the expense of possibility of change of a cartridge depending on model of the diagnosed car (Ford, GM, Chryslers, etc.), others are attached to requirements of the regional authorities and intended for use in certain regions of the world (Europe, Asia, the USA, etc.). Connection of the scanner is made to the onboard diagnostic DLC socket which purpose of conclusions is explained on an illustration.

 Attempts of connection to the DLC socket of the scanners other than GST OBD II or SSM it is fraught with failure of a contour of connection of the SSM monitor!


L models 2.0 and 2.5

1

Power supply from the battery

2

It is not used

3

It is not used

4

Signal from ECM to the SSM scanner

5

Signal from the SSM scanner to ECM

6

Clock signal of SSM

7
It is not used
8
 It is not used
9
 It is not used
10
 ISO 9141 CARB K-Line line
11
 It is not used
12
 Grounding
13
 Grounding
14
 It is not used
15
 It is not used
16
 It is not used

Models of 3.0 l

1

Power supply from the battery

2

It is not used

3

It is not used

4

It is not used

5

It is not used

6

Clock signal of SSM 1

7
It is not used
8
 Clock signal of SSM 2
9
 It is not used
10
 ISO 9141 CARB K-Line line
11
 It is not used
12
 Grounding
13
 Grounding
14
 It is not used
15
 It is not used
16
 It is not used

One more way of data read-out of OBD is connection to system of the personal computer equipped with a special cable and equipped with the software of OBD.

 Data read-out by means of scanners can learn more detailed information on the sites www .obdii.com, www .obd-2.com and www.obd-2.de.


The universal K-L-Line adapter serves for coordination of signals of RS-232 port and ISO-9141 (K-Line) and ALDL interfaces. Various cables allowing to make data read-out of OBD from cars of various brands can be connected to sockets of the adapter. The switches and elements of indication provided on the adapter allow to choose necessary operating modes and approximately to estimate quality of functioning of output lines. So, the luminescence of a green light-emitting diode with marking of L-Line testifies to connection of the line L with the mass of the car. Activation of a red light-emitting diode with marking K-Line confirms about presence on the line K of time of high potential at the moment. At the established connection with OBD system of the car the blinking of indicators can be imperceptible for an eye in view of the high speed of data exchange. Connection to the computer is made directly in 25-contact SOM port or in 9-contact SOM port by means of the transitional RS232 25-9 cable.


Some readers besides usual diagnostic operations allow at connection to the personal computer to make printing stored schematic diagrams of various equipment in memory of the module of management (if those are put in ECM), to program anticreeping system and control units of various devices of the car, and also in real time to observe signals in electric chains of the car.

On some models reading of the DTC codes brought in memory of OBD system can be made also with the help MIL/" which is built in in an instrument guard of the car of a control lamp of refusals check the engine", - see below.

Reading of the DTC codes

 More detailed information on reading of codes of malfunctions is provided in the user's guide to the scanner. The list of codes of malfunctions is provided in the Specification to the present Chapter.


Schemes of an arrangement of the interactive components used on the cars of systems of onboard diagnostics considered in the present manual are submitted on illustrations.

The scheme of an arrangement of interactive components of system of onboard diagnostics on the models equipped with system of onboard self-diagnostics of OBD II

1 — ECM
2 — the Control lamp of refusals of MIL/" check the engine"
3 — the testing mode Socket

4 — the Diagnostic DLC socket (under SSM or GST)


The scheme of an arrangement of interactive components of system of onboard diagnostics on models 2.0 and 2.5 of the l equipped with OBD Subaru

1 — ECM
2 — the Control lamp of refusals of MIL/" check the engine"
3 — the data read-out Socket from memory of the processor

4 — the testing mode Socket
5 — the Diagnostic DLC socket


The models equipped with OBD II

With use of the SSM scanner which is switched on in the normal mode (Subaru)

In the main menu (MAIN MENU) on the screen of the display select item {Each System Check} and press the YES key.

In the field by {System Select Menu} choose a bookmark {Engine Control System} and again press "YES".

After a conclusion to the screen of data on engine type, press "YES" once again.

In the field {Engine Diagnosis} select item { Diagnostic Code (s) of Display } and press "YES".

Further choose the subparagraph { Current Diagnostic Code (s) }, or { by History Diagnostic Code (s) }. Confirm a choice with pressing of the YES key and make reading of the displayed DTC codes.

With use of the SSM scanner which is switched on in the OBD (SAE) mode

In the main menu (MAIN MENU) on the screen of the display select item { 2. Each System Check } also press the YES key.

In the field by {System Select Menu} choose a bookmark {Engine Control System}. And again press "YES".

After a conclusion to the screen of data on engine type, press "YES" once again.

In the field {Engine Diagnosis} select item {OBD System} and press "YES".

In the menu {OBD Menu} select item { Diagnostic Code (s) of Display }, press "YES" and make sure of a conclusion of the DTC codes to the monitor screen.

With use of the GST (SAE) scanner

Act according to the instructions enclosed to the scanner.

The models equipped with OBD Subaru

With use of the SSM scanner

Act according to instructions.

Without use of the SSM scanner (on a control lamp of refusals of MIL/" check the engine")

Switch off ignition and connect the data read-out socket from memory of the processor.

Include ignition. If at ignition inclusion the control lamp of MIL is activated, pass to the following stage of check, otherwise check for existence of breaks and short circuits an electrical wiring of giving of food and grounding ECM, and also MIL lamp electrical wiring. Make necessary corrections.

Make sure of serviceability of highlighting a control lamp of refusals of a code of malfunction (DTC). Copy the identified codes, then switch off ignition and disunite the data read-out socket.

The control lamp of refusals (MIL) highlights the DTC codes brought in memory by ECM in the form of sequence of gleams of various length. Thus long gleams (duration about 1.3 seconds) designate decimal categories of a code, short (duration about 0.2 c) - single categories, the sequence of gleams lasting 0.5 seconds corresponds to a code of lack of DTC in memory of the processor.


Information contents of categories of a 5-digit code of a type of P0380

Categories of a code of a look P 0 3 8 0 have the following value (from left to right):

Category 1

P — the Power unit
B — the Body
With — the Chassis

Category 2 Code Source

0 — the SAE Standard
1 — Expanded - set by the producer

Category 3 System

0 — System in general
1 — System of admixture of air (Air/Fuel Induction)
2 — System of injection of fuel
3 — System ignitions/admissions of ignition
4 — System additional release control
5 — the Speed of the car and management of turns x/x
6 — Entrance and output signals of the module of management
7 — Transmission

Categories 4 and 5

Serial number of malfunction of a component or chain 00-99

Procedure of the general diagnostics of the car

 More detailed information on reading of codes of malfunctions is provided in the user's guide to the scanner. The list of codes of malfunctions is provided in Specifications to the present Chapter.


The models equipped with OBD II

Preparation

Lift the car over the earth, or tire out it on the roller stand.

 Remember that during check all four wheels of the car will rotate, - track that near wheels there were no tools and foreign subjects!


Check with use of the SSM scanner

 After completion of check and cleaning of memory of the processor make sure of absence remained not identified data.


Take the SSM scanner from a small suitcase and connect to it a diagnostic cable. Fill a working cartridge in the scanner.


Connect halves of the testing mode socket located at the left under the dashboard.

Connect SSM to the diagnostic DLC socket located also at the left under the dashboard.

 The DLC socket is intended for connection only of SSM or GST OBD-II scanners!


Include ignition (the engine do not start), then include power supply of the scanner.


In the main menu (MAIN MENU) on the screen of the display select item {Each System Check} and press the YES key.

In the field by {System Select Menu} choose a bookmark {Engine Control System}. And again press "YES".

After a conclusion to the screen of data on engine type, press "YES" once again.

In the field {Engine Diagnosis} select item {Dealer Check Mode Procedure} and press "YES".

After a conclusion to the question monitor screen "Perform Inspection (Dealer Check) of Mode?" enter confirmation, also by pressing the YES key.

Further act according to the displayed instructions. If after completion of procedure in memory of the processor any DTC remain, the relevant information will be displayed the monitor.

Release the parking brake, - the difference in the frequency of rotation of lobbies and back wheels can be the reason of operation of a control lamp of ABS, however it is not necessary to consider as a violation sign, - after completion of procedure of diagnostics of a control system of the engine do not forget to remove a code of malfunction of ABS from memory of the processor.

Check with use of the GST scanner

 After completion of check and cleaning of memory of the processor make sure of absence remained not identified data.


Connect halves of the testing mode socket located at the left under the dashboard.

Connect GST to the diagnostic DLC socket located also at the left under the dashboard.

 The DLC socket is intended for connection only of SSM or GST-OBD II scanners!


Start the engine, - previously make sure that the lever of the AT selector is in situation "P".

By means of the lever of selector/gear shifting activate sensors switches of provisions "P" and "N" of transmission.

For activation of the sensor switch of stoplights squeeze out a pedal of a foot brake.

Within about 40 seconds keep the frequency of rotation of the engine in range of 2500 ÷ 3000 rpm.

 On models without the built-in tachometer use a tachometer with inductive connection.


Transfer the selector lever to the situation "D" and establish the speed of the movement 5 ÷ 10 of km/h (3 ÷ 6 miles/h).

 On the AWD models do not forget to release the parking brake, - the difference in the frequency of rotation of lobbies and back wheels can be the reason of operation of a control lamp of ABS, however it is not necessary to consider as a violation sign, - after completion of procedure of diagnostics of a control system of the engine do not forget to remove a code of malfunction of ABS from memory of the processor.


By means of the GST scanner consider and copy the codes of malfunctions (DTC) brought in memory of the processor.

The models equipped with OBD Subaru

Check with use of the SSM scanner

Act according to the instructions provided in the subsection Check with use of the SSM scanner is higher.

Check without use of the SSM scanner

 On the AWD models do not forget to release the parking brake, - the difference in the frequency of rotation of lobbies and back wheels can be the reason of operation of a control lamp of ABS, however it is not necessary to consider as a violation sign, - after completion of procedure of diagnostics of a control system of the engine do not forget to remove a code of malfunction of ABS from memory of the processor.


Start the engine and warm up it up to the normal working temperature.

Switch off ignition and include neutral transfer (models with RKPP) / transfer the selector lever to situation "P" (models from AT).

Connect testing mode socket halves (it is painted in green color), then include ignition, - if there was an activation of a control lamp of refusals (MIL), pass to the following stage of check, otherwise check for existence of breaks and short circuits an electrical wiring of giving of food and grounding ECM, and also MIL lamp electrical wiring. Make necessary corrections.

On models from AT transfer the selector lever to the situation "N", then in "Р".

Start the engine and copy the MIL codes highlighted by a control lamp. If the lamp does not highlight any codes, pass to the following stage of check.

At least for one minute accelerate the car to the speed of 11 km/h (7 miles/h).

Lift the frequency of rotation of the engine to value over 2000 rpm. Copy the MIL codes highlighted by a lamp, - if no codes are removed by a lamp, therefore, refusal has other reason.

Cleaning of memory of system of self-diagnostics

 More detailed information on reading of codes of malfunctions is provided in the user's guide to the scanner.


The models equipped with OBD II

With use of the SSM scanner which is switched on in the normal mode (Subaru)

In the main menu (MAIN MENU) on the screen of the display select item { 2. Each System Check } also press the YES key.

In the field by {System Select Menu} choose a bookmark {Engine Control System}. And again press "YES".

After a conclusion to the screen of data on engine type, press "YES" once again.

In the field {Engine Diagnosis} select item {Clear Memory} and press "YES".

After on the screen of the monitor messages of "Done" and "Turn Ignition Switch OFF" are displayed, switch off the scanner, then turn a key in the ignition lock in the situation OFF.

 On l models 2.0 and 2.5 after completion of cleaning of memory of the processor it is necessary to make initialization of the electromagnetic valve of stabilization of turns of idling (IAC), - turn a key in the situation ON and before carrying out start of the engine, wait not less than 3 seconds.


With use of the SSM scanner which is switched on in the OBD (SAE) mode

In the main menu (MAIN MENU) on the screen of the display select item { 2. Each System Check } also press the YES key.

In the field by {System Select Menu} choose a bookmark {Engine Control System}. And again press "YES".

After a conclusion to the screen of data on engine type, press "YES" once again.

In the field {Engine Diagnosis} select item {OBD System} and press "YES".

In the menu {OBD Menu} select item { 4. Diagnosis Code (s) of Cleared }, press "YES".

After a conclusion to the inquiry screen "Clear Diagnosis Code?" enter confirmation by pressing of the YES key, then switch off power supply of the scanner and ignition.

 On l models 2.0 and 2.5 after completion of cleaning of memory of the processor it is necessary to make initialization of the electromagnetic IAC valve.


With use of the GST (SAE) scanner

Act according to the instructions enclosed to the scanner. On models 2.0 and 2.5 of l do not forget to make initialization of the IAC valve.

The models equipped with OBD Subaru

With use of the SSM scanner

Act according to the instructions given above.

Without use of the SSM scanner (on a control lamp of refusals of MIL/" Check the engine")

Switch off ignition and include neutral transfer (models with RKPP) / transfer the selector lever to situation "P" (models from AT).

Connect testing mode socket halves (it is painted in green color), then include ignition, - if there was an activation of a control lamp of refusals (MIL), pass to the following stage of check, otherwise check for existence of breaks and short circuits an electrical wiring of giving of food and grounding ECM, and also MIL lamp electrical wiring. Make necessary corrections.

On models from AT transfer the selector lever to the situation "N", then in "Р".

Start the engine and a minimum for one minute accelerate the car to the speed of 11 km/h (7 miles/h).

Lift the frequency of rotation of the engine to value over 2000 rpm. Copy the MIL codes highlighted by a lamp and make necessary recovery repair (the list of the DTC codes is provided in Specifications).

Switch off ignition and disunite the testing mode socket.

Connection of the personal computer to onboard system of self-diagnostics of OBD II by means of the interface BR16F84-1.0 controler under protocols of the SAE standards (PWM and VPW) and ISO 9141-2

 The controler is not intended connections to onboard systems of self-diagnostics of the first generation (OBD I)!

Models of production of the company GM, PWM - Ford, to ISO 9141-2 - Asian and European models meet the VPW standard.


General data

The scheme of the organization of connection is submitted on an illustration.


The considered device represents the microcontroller executed on the KMOP (CMOS) technology. The device plays a role of the elementary scanner and is intended for reading of diagnostic codes and data of OBD II system (engine turns, temperature of cooling liquid and the soaked-up air, load characteristics, a consumption of the air coming to the engine, etc.) within the SAE J1979 standard via the tire of any execution (PWM, VPW and ISO 9141-2).

Main destination

For connection to the computer of rather 3-wire wire, connection to the diagnostic socket is carried out by a 6-wire wire. The supply voltage moves on the controler via the 16-contact diagnostic OBD socket.

Recommendations about application

For connection of the device to the car not screened cable, no more than 1.2 m long can be used that has special value when using the PWM protocol. When using a cable of bigger length it is necessary to reduce resistance of resistors on an entrance of the device (R8 and R9 or R15). When using a screened cable, the screen should be switched-off for the purpose of decrease in capacity.

The cable for connection to a serial port of the computer can also be not screened. The device steadily works with a cable up to 9 m long. With much bigger length of a cable it is necessary to use more powerful communicator of RS 232.

The topology of electric connections is any. At the increased humidity use the additional shunting condensers.

The free software (browser) for reading of codes and data can be downloaded from the sites of producers or the site of our arus.spb.ru publishing house and is intended for use under DOS. The insignificant size of a program application in option "under DOS" allows to accomodate it on the loading diskette DOS and to use even on the computers equipped with the software, incompatible with DOS. An optional condition is even existence in the computer of the hard drive.

General principles of data exchange

 If the opposite is not stipulated especially, all numbers are given in a 16-richny format (hex). The decimal format is designated by dec tag.


Data exchange goes on three-wire consecutive connection without application of an initsializatsionny exchange of office messages (handshaking). The device listens to the channel on existence of messages, executes the accepted commands and transfers results to the personal computer (PC) then immediately comes back to the listening mode. The data entering the controler and proceeding from it are organized in the form of a chain of the bytes which are consistently going one after another, first of which is control. The Obychnokontrolny byte represents number from 0 to 15 dec (in decimal calculation) (or 0-F hex), the describing number of the information bytes following further. So, for example, the 3-byte team will look as follows: 03 (control byte), 1st byte, 2nd byte, 3rd byte. The similar format is used as for the entering commands for poll of onboard system of self-diagnostics, and for the outgoing messages containing the requested information. It is necessary to notice that in control byte only four younger bits are used, - the senior bits are reserved under some special teams and PC at initialization of connection with the controler and coordination of the protocol of data transmission can be used, and also the controler for control of errors of transfer. In particular, in case of a mistake by transfer, the controler makes installation of the senior meaning bit (MSB) of control byte in unit. By successful transfer all four senior bits are established in zero.

 There are separate exceptions to the rules of use of control byte.


Initialization of the controler and onboard system of self-diagnostics

To start data exchange of PC has to make installation of connection with the controler, then initialize the controler and the channel of data of OBD II.

Connection installation

After connection of the controler to PC and the diagnostic OBD socket its initialization for the purpose of prevention of the "lags" connected with noise in consecutive lines has to be made in case their connection was made before inclusion of power supply of the controler. The simplest check of activity of the interface is at the same time made. First of all the one-byte signal of 20 hex perceived by the controler as command for connection installation is sent. In reply the controler instead of the control sends the only byte of FF hex (255 dec) and passes into a waiting mode of reception of data. Now PC can pass to initialization of the channel of data.

 This case is one of the few when the controler does not use control byte.


Initialization

At this stage initialization of the protocol under which data exchange will be made, and in case of the ISO protocol – initialization of onboard system is made. Data exchange is made on one of three protocols: VPW (General Motors), PWM (Ford) and ISO 9141-02 (Asian/European producers).

 There is a set of exceptions: so, for example, at poll of some models of Mazda cars the "fordovsky" PWM protocol can be used. Thus, at emergence of problems of transfer it is necessary first of all to try to use any other protocol. The choice of the protocol is made by transfer of the combination consisting of control byte of 41 hex and the byte defining protocol type following directly it: 0 = VPW, 1 = PWM, 2 = ISO 9141. So, for example, at the command of 41 02 hex initialization of the ISO 9141 protocol is made.


In reply the controler sends control byte and byte of a state. The MSB installation of control byte speaks about existence of problems, thus the byte of a state following it will contain the relevant information. At successful initialization the control byte of 01 hex specifying that the verification byte of a state follows further is sent. In case of the VPW and PWM protocols the verification byte represents a simple echo of the byte defining the protocol (0 or 1, respectively), at initialization of the ISO 9141 protocol it will be the digital key returned by the onboard OBD processor and defining which of two versions of the protocol which are slightly differing from each other will be used.

 The digital key has purely information appointment. It is necessary to notice that initialization of the VPW and PWM protocols happens much quicker as demands only transfer of the relevant information to the controler. On the models meeting the ISO standard, initialization takes about 5 seconds spent for the information exchange of the controler with the onboard processor made with a speed of 5 baud. It is necessary to pay attention of the reader that on some models of cars of ISO family 9141 initialization of the protocol stop if the request for issue of data is not transferred during a 5-second interval, - told mean that PC has to make automatic delivery of inquiries each some seconds, even in the single mode.


After installation of connection and initialization of the protocol regular data exchange, consisting of the inquiries arriving from PC and answers issued by the controler begins.

Data exchange order

Functioning of the controler when using protocols of ISO 9141-2 and SAE family (VPW and PWM) happens according to a little various scenarios.

Exchange under the SAE protocols (VPW and PWM)

At data exchange under these protocols there is a buffering of only one shot of data that means need of a specification subject to capture or return of a shot. The onboard processor can transfer the packages consisting more than of one shot in some (rare) cases. In such situation the inquiry has to repeat until all shots of a package are not accepted.

The inquiry is always formed as follows: [Control byte], [Inquiry according to the SAE standard], [Number of a shot]. As it was already mentioned above, the control byte usually represents the number equal to full number of the following bytes behind it. The inquiry is made out according to the SAE J1950 and J1979 Specifications and consists of heading (3 bytes), sequence of information bytes and byte of control of a mistake (CRC). Let's notice that while information on inquiry is formed in strict compliance with the SAE Specifications, the consumer of control byte and number of a shot is the interface controler.

At a successful completion of procedure the response message always has the following format: [Control byte], [The answer according to the SAE standard]. The control byte, as well as earlier, defines number of the information bytes following it. The answer according to requirements of the SAE standard consists of heading (3 bytes), a chain of information bytes and byte of CRC.

At failure the 2-byte response message is sent: [Control byte], [State byte]. Thus in control byte the MSB installation is made. Four younger bits form number 001 testifying that the control is followed by the only byte - state byte. This situation can arise rather often as Specifications allow possibility of a lack of distribution the onboard processor of data, and also transfer of incorrect data in a case when the inquiry does not conform to the standard supported by producers of the car. Also the situation when required data are absent in random access memory of the processor of time at the moment is possible. When the controler does not receive the expected answer, or obtains the damaged data, the MSB installation of control byte is made, and after the control the state byte is given.

At collisions in the tire the interface develops the only byte of 40 hex which is control byte with the nullified younger bit. The similar situation can arise rather often when loading a car tire messages of higher than at diagnostic data of a priority, - the computer has to repeat initial inquiry.

Exchange under the ISO 9141-2 protocols

The ISO 9141-2 standard is used by most of Asian and European producers of automotive vehicles. The structure of the formed inquiry PC a little than differs from used in the SAE standards, with only that difference that the controler does not need information on number of a shot and the relevant data should not be present at a package. Thus, the inquiry always consists of control byte and the chain of the information bytes including checksum following it. As the response message the controler simply relays the signals created by the onboard processor. The control byte in the response message is absent therefore PC perceives the arriving information a continuous stream until the chain does not interrupt the pause in 55 milliseconds reporting about end of information package. Thus, the response message can consist of one or more shots according to requirements of the SAE J1979 specifications. The controler does not make the analysis of shots, does not reject not diagnostic shots, etc. PC has to make by own forces processing of the arriving data with the purpose of exarticulation of separate shots by the analysis of heading bytes.

 Responses to the majority of inquiries consist of the only shot.

The modifications made in the interface controlers of the latests version

 All information bytes are transferred in a 16-richny format (hex).

The symbol of XX means the uncertain, reserved or unknown byte.


The main differences of process of data transmission under the SAE and ISO 9141 protocols, characteristic for the interface controlers of the latests version, and also a data transmission order under the ISO 14230 protocol are given below:

1) ISO 9141 standard: The address byte is added;
2) ISO 9141 standard: Return not of one, but both key bytes is carried out (the additional byte comes back also in the SAE modes, however here it is not used);
3) Support of the ISO 14230 protocol is added.

Connection installation

The order of installation of connection did not change:

Sending: 20
Reception: FF

Protocol choice

The protocol gets out in as follows:
VPW:
Sending: 41, 00
Reception: 02, 01, XX
PWM:
Sending: 41, 01
Reception: 02, 01, XX
ISO 9141:
Sending: 42, 02, adr, where: adr - address byte (usually 33 hex)
Reception: 02, K1, K2, where K1, K2 - key bytes of ISO
Or:
82, XX, XX (error of initialization of ISO 9141)
ISO 14230 (fast initialization):
Sending: 46, 03, R1, R2, R3, R4, R5, where: R1 ÷ R5 - the message on the beginning of request of ISO 14230 for connection installation, usually R1 ÷ R5 = C1, 33, F1, 81, 66
Reception: S1, S2, … … …, where S1, S2, … … … - the message on the beginning of the response of ISO 14230 to connection installation

 Can consistently be transferred more than one ECU. As the answer the negative code of the answer can be used.

The typical affirmative answer looks as follows: S1, S2, … …. = 83, F1, 10, S1, E9, 8F, BD
ISO 14230 (slow initialization):
Similar to ISO 9141

Remark and comments

If use of the controler for data transmission only on any to one is planned or to two of protocols, excess components can be excluded. For example, at the organization of the scheme under the VPW (GM) protocol in a wire of connection of the controler to the car only three veins of an electrical wiring (plug 16, 5 and 2) will be required.

If the PWM protocol is not used, the R4, R6, R7, R8, R9, R10, T1, T2 and D1 elements can be excluded.

At refusal of an exchange under the ISO protocol elements are subject to an exception: R15, R16, R17, R18, R19, R21, T4 and T5.

Refusal of use of the VPW protocol allows to exclude the following elements: R13, R14, R23, R24, D2, D3 and T3.

Coal and film resistors with the 5 percent admission of resistance are used.

Pay attention to lack of the button of emergency reset (RESET), - in case of need such reset can be made by a controler detachment from the automobile socket (reset of the interface processor will happen automatically). Restart of the software on PC leads to repeated initialization of the interface.