8/12/2019 VW Initialization 2 6 Seconds

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To: State I/M Program Administrators June 30, 2010

Subject: OBD Communication Initialization

Overview:

Volkswagen has found that some inspection equipment (or handheld OBD scan tools) havetrouble establishing communication with a:

1999 MY VW Golf 1.9L TDI (diesel) 66kW;2000 MY VW Jetta 1.8L Turbo (gasoline) 110kW; or2001 MY VW Jetta 2.0L (gasoline) 85kW

and may not be able to establish communication at all with these vehicles or may only be ableto establish communication with the transmission control module (TCM) (for automatictransmission equipped vehicles). If communication is established only with the TCM, only aportion of the OBD information will be accessed and incorrect pass/fail decisions may be made.There may be additional older models that are affected but as of this time, VW has not beenable to identify any other affected vehicle models.

Volkswagen has found that the ISO 9141-2 communication protocol implementation byVolkswagen, while within the specifications, may be the root cause as scan tool or equipmentmanufacturers may not have anticipated such an implementation. Attached to this letter is adocument defining how Volkswagen implemented the initialization sequence on the affectedvehicles and how equipment should be configured / designed to ensure successful

communication with these vehicles.

Information for I/M Program Administrators:

If a State is seeing a high rate of communication problems with these affected vehicles, it islikely that their inspection equipment might not tolerate the implementation of the ISO 9141-2initialization sequence used by Volkswagen. The State should consult with their equipmentvendors and the attached reference document to determine if the equipment can easily bechanged to work correctly with these vehicles. The Issue Descriptionbelow provides a shortdescription of the technical background underlying this communication incompatibility.

Further, as these vehicles are compliant with the ISO 9141-2 specifications, there is no fix or

change that can be made for the vehicle to make it communicate differently.

Communication with only the TCM may occur for vehicles equipped with automatictransmissions. Indications that communication was only established with the TCM include:

The only readiness monitor supported on the vehicle is comprehensive components;The only module address/ECU ID that was noted during the test was $1A; orThe PID count of the ECU (number of mode $01 PIDs supported) is reported as 5.

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Regardless of whether no communication with any module is occurring or communication withonly the TCM is being established, the incompatibility likely is due to the issue described belowand a change to the equipment initialization procedures will be needed to get complete OBDinformation from the vehicle and make accurate pass/fail decisions.

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Backup for I/M equipment supplier

Issue Description:

The ISO 9141-2 communication protocol requires a 5 baud (slow initialization) sequence to besent from the tool to the car and then for the car to validate the sequence and send a responseto the tool to confirm the protocol. Volkswagens implementation is such that the engine controlmodule (ECM) waits for the entire 5 baud sequence to be received before attempting to validate

it. As a result, the ECM is not able to receive any different initialization pattern for approximately2.6 seconds1after the indication of the beginning of any initialization pattern.

The issue can arise when inspection equipment does not account for this amount of timebetween initialization attempts of ISO 9141 and/or ISO 14230-4 (KWP) fast initialization (e.g., ifan unsuccessful KWP initialization attempt is followed less than 2.6 seconds later by an ISO9141 initialization attempt). The ECM cannot separate the two and will not recognize the 5 baudpattern as valid. Inspection equipment needs to wait for a full 2.6 seconds after attempting aKWP fast initialization before it sends an ISO 9141-2 slow initialization request in order for theECM to properly receive the 5 baud sequence.

Further details are provided in the attachment K-Line Communication Description and should

be used by equipment manufacturers to understand and address this issue.

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