With Integrated Fault-Diagnosis System (Flash Codes)

Fault Diagnosis With The Integral Self-Diagnostics LH 2.4, LH 2.4.1 and LH 2.4.2 Systems





The self-diagnostics systems have two main applications:
- Fault diagnosis, stored faults
- Component and signal testing

Important:
-M1989: Only the "CHECK ENGINE" lamp (MIL) in the main instrument display panel is used for reading faults.

M1990-: The "CHECK ENGINE" lamp (MIL) in the EDU is used for reading faults (not cars without EDU).


Stored faults

Faults which occur intermittently are often hard to find. The LH 2.4 has an integral memory with which it is possible to pinpoint such a fault later on and rectify it.

By following the instructions below, which describe how to activate the system's memory function, the "Check ENGINE" lamp (MIL) in the car's main instrument display panel will provide information on stored faults in the form of flashes (lamp-flash codes).

A certain combination of short flashes, e.g. 1+2+3+2+2, stands for a particular fault. You then consult a fault code list to find out what the fault code 12322 means and rectify the fault. Similarly, fault codes for fault No. and fault No.3 can be activated and from the flashes of the "Check ENGINE" lamp (MIL) the code can be interpreted in the fault code list.

Up to three faults can be stored in the control module's memory. In connection with fault diagnosis they can be activated to provide information about the nature of the fault. Serious faults are given priority, which in practice means that they must be rectified before the control module stores any less serious faults.

Important: If a serious fault develops repeatedly it will be recorded in the memory each time it occurs and cause the "Check ENGINE" lamp (MIL) to light up. When the fault has been rectified it may be necessary to clear the memory so that the fault code will "disappear". In doubtful cases you should always take the car out on test.


Component and signal testing

It is a good idea to carry out these tests in conjunction with "Fault diagnosis, stored faults".

Testing includes checking the operation of certain key components in the LH system and checking important control module signals.

In these tests the "CHECK ENGINE" lamp (MIL) will also flash codes with the same structure as those for stored faults. However, in this case the code is not a fault code but an identification code which indicates the component or signal that is being tested. For example, if the "Check ENGINE" lamp (MIL) flashes the code 12413, the table for component and signal testing shows that the EVAP canister purge valve is being tested. The noise made by the valve opening and closing should be heard at the same time.

Important: All code flashing and testing will come to an end when the ignition switch is turned to the OFF position.