Description of On Board Diagnosis

NOTE:
^ At temperatures below 0 °C (32 °F), the cabin temperature sensor and blended air temperature sensor cannot be tested. Always check connections to connectors before carrying out fault diagnosis in other areas.

^ All measurements should be taken from the back of connectors. Input or output voltages should only be measured with the ignition on or with the engine running.


Fault Diagnosis, ACC Generation 2
System No.2 applies to ACC (start by using the ISAT scan tool to read any faults).

The ACC program has an integrated self test program which carries out a number of tests while the ACC control module is operating. The self test program is even run during initiation (when ignition is first switched on), either by simultaneously pressing in the AUTO and VENTILATION buttons or using the ISAT scan tool.

For a complete self test and calibration, the program must run for at least 35 seconds.

Each fault which is discovered by the self test program will be given a diagnostic trouble code which indicates what type of fault it is.

When the ignition is switched on for the first time, the number of faults discovered is shown on the display while the initiation program is running. In addition, the number of faults can also be read later by first pressing OFF and then AUTO.

The stored diagnostic trouble codes can be read from the memory using the ISAT scan tool. Stored diagnostic trouble codes are erased, either using the ISAT scan tool (command 900) or by pressing AUTO and VENTILATION.

Unplug connectors and check pins for damage. Refit connectors and erase all diagnostic trouble codes. Restart the system and check if the fault is still present.

When first detected, every fault is given a diagnostic trouble code which corresponds to a permanent fault. If the fault disappears again, the diagnostic trouble code is changed to intermittent. Fault codes can either be erased using the ISAT scan tool (command 900) or by pressing AUTO and VENTILATION.

All voltage levels given in signal level tables have been measured by using a digital multimeter. All signals around the 12 V level are proportional to battery positive voltage, and should therefore only be used as a guide.

0 V signals show ground voltage level but can, on a sensitive digital multimeter, give an indication slightly above 0 V.