Before Changing A Control Module

Before Changing A Control Module

We know from experience that the majority of control modules returned for repair under warranty are in perfect working order. In these cases, replacement of the control module has not cured the fault.

The main instrument unit is made up of 3 principal components, each of which is replaceable:
- Instrument unit
- Control module (electronic unit MIU)
- Odometer display

When there is a fault in the main instrument unit it is often difficult to determine in which component the fault is present. Saab Automobile and the manufacturer have jointly analysed the defective main instrument units exchanged during the warranty period. From the experience we have thus accumulated we can give the following recommendations for deciding which component should be changed when repairing a main instrument unit.
- If communication with Tech 2 is correct and the reading obtained for the control module input concerned is OK, the control module is probably not the cause of the fault. Change the instrument unit or odometer display, depending on the fault symptoms.
- If communication with Tech 2 is troublesome and difficulty is experienced with the "Activate" functions, etc., then the control module is probably at fault and should be changed.

Go through the following points before changing the control module:
1 Check all grounding points and the power supply for the control module.
2 Using the diagnostic tool, check that all readings are plausible.
3 Using the diagnostic tool, check that all activation commands produce the desired result.
4 If the fault persists, the control module must be changed.
5 It is important to ground yourself, by touching the engine for example, before handling a control module. Never touch the control module pins.

A new electronic unit should be ordered for a given chassis number and current odometer reading. When the control module has been refitted in the car, the car will not start until TWICE has been programmed.