Fault codes cannot be read out;
– With ignition switched off
– If "AHE" system not recognized / not displayed:
Check fuses F6-A5 and F1-A1, replace if necessary and switch on auxiliary heater.
Check whether diagnostic cable to auxiliary heater control unit is installed.
Check for open-circuit in diagnostic cable (to control unit plug A, pin 13/1) or a plug connection.
Check whether control unit is able to diagnose. Only control units part nos. 000 446 05 29 and 000 446 06 29 (for GGVS) can diagnose.
– If "switch on ignition" appears in HHT display when ignition switched on, check fuse terminal 15 (pin 2) of diagnostic socket.
– If fault code – is displayed on vehicles with vehicle diagnosis system / flexible service system, diagnostic cable to display computer may be open-circuited.
– If HHT display remains dark:
Check fuse terminal 30 (pin 3) and ground connection (pin 1) of diagnostic socket.
On other vehicles check whether multiplexer is in order.
With this HHT display assignment of pin nos. 4 to 14 is possible, depending upon number of installed systems that can be diagnosed.
HHT display:
AHE Short test / system selection Commercial vehicle
Diagnostic socket contact
XX
System does not respond
Possible cause
- Diagnostic cable
- Control unit voltage supply
- Control unit