Fault Tracing Procedures

Self-diagnosis With Fault Indication:

The ECC control module can detect faults in the system, store diagnostic trouble codes (DTCs) and indicate what is wrong if required.

Fault Warning To Driver:





If there is a fault, the system informs the driver by flashing the LEDs by the AC and REC switches for 20 seconds.
A fault warning is given when the fault is discovered, and each time the ignition is switched on and the fault still remains.

Fault Displays To Mechanics:

- DTCs can be read off and deleted via the Volvo Diagnostic Key (Scan Tool) P/N 998 8670.
- There are three different settings which can be selected for reading off DTCs and acknowledgment codes and enter control codes.
- Mode 1 for reading off DTCs. For fault-tracing description.
- Mode 2 for acknowledgement codes. For code description.
- Mode 4 for control and transmission codes. For code description.
- [1][2]Description of On-Board Diagnostics

Control Module Action In The Event Of A Fault:





The control module is programmed to make the best of the situation if a fault is discovered. The control module then ignores the faulty signal and selects a preset replacement value. The control module can also stop faulty outputs being activated. Some examples:
- If a passenger compartment sensor is faulty, the control module ignores the faulty signal from it and uses the control signal from the temperature switch on that side instead.
- If a damper motor fails to change setting because the damper is stuck, the damper motor switches off after 12 seconds. It cannot then be started until the next time the ignition is switched on.

Other Fault Symptoms:





- For fault symptoms which are not covered by DTCs, we recommend connecting the test unit (breakout box) between the control unit and air-conditioning system. Run basic tests and read off all input and output signals. Test Procedures
- Input and output signal values are shown in the table of signals and test points. See On-Board Diagnostic unit and Test Modes.
- If symptoms only occur intermittently, the DTCs stored may give some guidance. For mechanical symptoms, refer to "Fault-tracing, A/C system, See On-Board Diagnostic unit and Test Modes."
- [1][2]Description of On-Board Diagnostics