The control module can store a maximum of 5 faults. Recognized faults are stored in the control module fault memory, coded as a fault code number.
A distinction can be made between the recognition of faults and their storage as follows:
Fault existing at the moment (current fault)
Fault existed but is no longer present (stored fault)
The fault memory is not erased when the supply voltage is interrupted, e.g. when disconnecting the battery.
The faults stored can be read out at the diagnostic socket using the HHT only with the "Ignition ON" and the "Heater unit ON".
Procedure for current faults:
Work through faults as described in the HHT display.
Procedure for stored faults:
Erase fault memory. Switch heater unit off and on again. Read out fault memory again. Rectify any stored faults.
Note
No fault codes can be read out if it is not possible to switch on the heater unit.
Faults of this type must be eliminated beforehand.
If "AHE" is not displayed after the short test when the heating is switched on, switch the heater unit off and on again several times if necessary.
If the system is not recognized in spite of this:
Check whether the diagnosis line is open-circuited.