Description of On-Board Diagnostics

Fault diagnosis using the integrated fault-diagnosis system (LH 2.4), 900S (US)

The fault-diagnosis system has two principal applications:
- Fault diagnosis, faults detected and stored in the memory.
- Component and signal testing.

Faults stored in the memory

Faults that occur intermittently are often hard to trace. The LH 2.4 has an integral memory that stores information on such faults so that you can later identify and rectify them.




By following the instructions below which describe how to activate the system's memory facility, the "CHECK ENGINE" lamp on the car's instrument panel will flash and provide information on any faults that have been detected.

A certain combination of short flashes, e.g. 1+2+3+2+2, stands for a particular fault. By consulting the list of fault codes to find out what the fault code 1 2 3 2 2 stands for, you can identify the fault and rectify it. This procedure can be repeated for fault No.2 and fault No.3, whereupon the CHECK ENGINE lamp will flash new codes which enable you to identify the faults from the list of fault codes.

Up to three faults can be stored at a time in the control module memory, which can be accessed as described above and provide information on the nature of the fault. Serious faults are given priority, which means that these must first be rectified before the memory can store information on minor faults.

Note: If a serious fault occurs repeatedly, each occurrence will be recorded in the memory and the "CHECK ENGINE" lamp will light up. Once the fault has been rectified, it may be necessary to clear the memory by erasing all its contents to delete any additional codes for the same fault. In doubtful cases, take the car out on a road test.


Component and signal testing

This testing can best be carried out in conjunction with diagnosis of stored faults.

Testing incorporates a function check of certain key components in the LH system and a check of important signals from the control module.

In these cases, the "CHECK ENGINE" lamp flashes codes in the same way as for stored faults. However, this time the code is not a fault code but an identification code for the component or signal being tested.

For instance, if the "CHECK ENGINE" lamp flashes code 1 2 4 1 3, reference to the table of identification codes for component and signal testing will show that the CP valve on the charcoal filter is being tested and that you should hear the valve opening and closing.

Note: All code indication and testing will be aborted when the ignition is switched off.