On Board Diagnostic (OBD), Function

On Board Diagnostic (OBD), Function

The instrument cluster is controlled by a microprocessor and has extensive On Board Diagnostic (OBD) capability. If malfunctions occur in any of the system components, corresponding DTCs are stored in the Diagnostic Trouble Code (DTC) memory of the instrument cluster.

If OBD recognizes instrument cluster malfunctions related to the:

- odometer
- speedometer calibration

the trip odometer display will change to show "dEF."

In this case, replace speedometer.

Other malfunctions recognized by OBD will not cause the trip odometer display to change as described above.

Before performing any troubleshooting or inspection, always begin by checking for DTCs using the On Board Diagnostic (OBD) program. DTCs stored in memory are retrieved/checked with VAG 1551 scan tool or VAS 5051 tester in mode "Self Diagnosis".

Where applicable, also use VAS 5051 tester in mode "Guided Fault Finding"

OBD program application notes.

OBD program application notes
Always confirm vehicle VIN and instrument cluster software version as per section title above. Confirm instrument cluster software version by initiating OBD program and reading information in display.

Information in this section also applies to replacement instrument clusters with software version D26 installed in vehicles through VIN 8N_040000.

Vehicles from start of production through VIN 8N_040000 contain instrument clusters with software versions through D24 have limited Diagnostic Trouble Code (DTC), Read Measuring Value Block and Adaptation information not specifically covered in this section.

Information on clusters on vehicles up to VIN 8N_040000 with software versions through D24 are contained in section "Instrument cluster On Board Diagnostic (OBD) through VIN 8N_040000 and software versions D24".

Message "dEF" On Trip Recorder Display

If the control module in the instrument cluster detects a malfunction in its permanent memory, the letters "dEF" will appear on the trip recorder display.

- If "dEF" appears on the display, replace the instrument cluster.

Notes On Replacing Instrument Cluster

- The instrument cluster must not be disassembled.
- If necessary, the instrument cluster can be replaced with an exchange unit (where applicable).
- Complete the damage report form and return it together with the malfunctioning instrument cluster.
- Malfunctioning units must always be returned in their original packing.
- Various input values must be adapted to replacement speedometer.