Description of On-Board Diagnostics

General information

The Climatronic control module receives information from various electrical and electronic sensors. This information is processed by the control module according to specified values and then provides corresponding output signals that control electrical components (actuators).

The Climatronic control module -J255- is integrated into the A/C Control Head -E87- and cannot be serviced separately. To enable recognition of component malfunctions or if there is an open circuit, the control module is equipped with Diagnostic Trouble Code (DTC) memory.

Should a malfunction be detected in a monitored sensor or component, it is stored in DTC memory.

When malfunctions which have a permanent adverse effect on the operation of the Climatronic are stored in DTC memory, the A/C control head -E87- display flashes for approx. 15 seconds when the ignition is switched on. If there are DTCs that do not cause the display to flash, the Climatronic control module allows the Climatronic to continue to operate in emergency mode at the settings set on the display.

To determine malfunctions detected by OBD, initiate the On Board Diagnostic program and retrieve stored information using the VAG 1551/1552 Scan Tool (ST) or VAS 5051 Vehicle Diagnostic Testing and Information System.

Malfunction information displayed by the scan tool is listed on DTC tables that contain notes on possible causes and repairs.

Sporadic malfunctions (indicated in the readout by "SP") are automatically canceled if not repeated in the next 50 engine starts.


NOTE:
Some components and functions of the Climatronic are not monitored by OBD (e.g. Interior Temperature Sensor Fan V42). If there is a specific complaint and no malfunctions are recognized after checking the Diagnostic Trouble Code (DTC) memory, refer to the information listed below.


Additional information:
- Climatronic, servicing
- A/C refrigerant system, servicing
- Wiring diagrams See "Electrical Wiring Diagrams, Troubleshooting & Component Locations"
- Information covering symptoms/causes and corresponding "Service Fixes" Technical Bulletins.