With LH System Tester

Fault diagnosis with LH system tester, LH 2.2 and LH 2.4

When carrying out fault diagnosis, make absolutely certain that you refer to the appropriate wiring diagram for the model year and LH system concerned.

Note:
- Before starting fault diagnosis with the LH system tester, it is advisable to use the integrated function on LH 2.4 cars for identifying data on any intermittent faults recorded in the control module. See under "Fault diagnosis with integrated fault diagnosis system, LH 2.4"
- It is important to do this first, since connection of the LH tester to the control module interrupts the module's power supply, with the result that any fault information stored in its memory will be erased and the opportunity to identify any intermittent faults will be lost.
- This will also occur if either of the battery cables is disconnected.


Fault diagnosis work - general procedure

The words "Check the wiring between xx and yy" are used frequently in the fault diagnosis charts. Sometimes the wiring may run through different types of connector and, by implication, these must also be checked for circuit continuity and short circuiting. Be alert to the possibility of interference from components connected to the wiring concerned. Also check that the wiring is in good condition and not the cause of defective grounding. Always make absolutely certain that you refer to the correct wiring diagram for the car model, model year and type of LH system concerned.

Note: Reference values for some of the parameters that are to be checked are preprogrammed in the microprocessor incorporated in the LH system tester. In some cases the nominal values fall within very narrow limits. Consequently, under certain conditions, a fault may be indicated when, in fact, no fault exists. This can only happen in extreme situations which are far removed from normal driving conditions. Examples of spurious faults that may be indicated under such extreme conditions include the following: