Before Changing A Control Module

It has been found from experience that the majority of control modules returned for repair under warranty are in perfect working order. In these cases, changing the control module has obviously not corrected the fault. Therefore, go through the following points before changing the control module:
1. Check all grounding points and the supply of power to the control module.
2. Use the diagnostics instrument to check that all readings are plausible (several readings may have a bearing on a particular function).
3. Check with a diagnostic tool that all functions are operating. (A fault in one output circuit can affect another output circuit).
4. If the fault persists, the control module must be changed.
5. When handling control modules it is important to ground yourself first, such as by touching the engine or bonnet. Avoid touching the control module's pins.