Diagnostic Manual, Info./Comm., Volume 1
Diagnosis - Diagnostic Trouble Code (DTC) Memory
Note regarding HHT:
The trip computer control module (N41) receives all the signals from the external sources via CAN data bus. Direct diagnosis of the incoming signals using HHT is therefor not possible.
To narrow the search for the possible fault cause it is important to observe functionality of other systems. In this case for the faulty instrument cluster (A1) indicators gauges or displays. For example incorrect vehicle speed displayed on the speedometer in the instrument cluster can be caused by the faulty traction systems control module (N47) which sends VSS signal via CAN data bus. Incorrect VSS signals would cause erroneous displays of fuel consumption and range on the trip computer.
It is recommended to read-out the respective actual values (VSS signal) using HHT with the instrument cluster (A1) or traction systems control module (N47) options.
The incorrect fuel consumption can be caused by the incorrect signal from the engine control module (N3/10). It is important therefor to readout with HHT the actual values from the engine control module (N3/10).
Incorrect reading of the fuel gauge in the instrument cluster (A1)) which could be caused by the faulty fuel level sensor (M3/3b1) will hinder the operation of the trip computer.
If the problem with the trip computer lies only in the trip time function, it indicates faulty trip computer control module (N41) since the needed information for that function is determined within control module itself.
Refer to the trip computer function description.
The values correspond to the time of supplement edition and they may change