On Board Diagnostic Description

OBD System Capabilities:

1) Climate control does not operate during the OBD program sequence (A/C compressor, coolant fan, etc., are not controlled)

- The A/C control head -E87- (for automatic climate control) and A/C clutch control module -J153- (for A/C with manual control) are equipped with Diagnostic Trouble Code (DTC) memory. If a malfunction occurs in a monitored sensor or component, a code is stored in DTC memory.
- Always check DTC memory as a first test step before attempting any repairs.
- Malfunctions that occur intermittently are identified by the system as "sporadic" and are indicated by "/SP" on the right side of the VAG1551 scan tool display.
- The A/C clutch control module -J153- (for A/C with manual control) distinguishes between 6 different malfunction types, and stores the corresponding Diagnostic Trouble Codes (DTC) only until the ignition is switched off.
- The A/C control head -E87- (for automatic climate control) distinguishes between 19 different malfunction types, and stores the corresponding Diagnostic Trouble Codes (DTC) until DTC memory has been erased using the VAG1551 scan tool.
- The On Board Diagnostic (OBD) program requires the use of the VAG1551 scan tool in "Rapid data transfer" operating mode 1.
- Data transfer from the VAG1551 scan tool is only possible with the ignition switched on, or with the engine running at less than 4000 RPM. At higher engine speeds, data transfer is interrupted.
- OBD functions include storing, checking, erasing, and output Diagnostic Test Mode (DTM), but there are also additional features including basic setting, A/C control head (control module) identification, and control module coding.
- Operating mode 2 (Blink code output) cannot be used for A/C heating electronics diagnosis. Operating modes 3 (Self-test) and 4 (dealership identification) apply only to the scan tool and are described in the VAG1551 scan tool operating instructions.
- A malfunction that is recognized for an extended period of time is identified as a "static" malfunction and stored as a Diagnostic Trouble Code (DTC). When the malfunction is no longer recognized after a certain period of time, it is identified as a "sporadic" malfunction. The evaluation process is constantly repeated.
- A DTC is converted from "static" to "sporadic" only if it is no longer recognized after a certain period of time.
- If a "sporadic" malfunction is no longer recognized after a certain period of time,the corresponding DTC is automatically cleared.