Component Tests and General Diagnostics
Important points to remember
1 The diagnostics socket is green and located under the right-hand front seat.The socket is protected by a plastic cover held in place by screws of bayonet coupling type.
2 During diagnosis the ignition switch must always be turned to the Drive position.
3 The EDU system has system number 1 in the ISAT.
4 Obtain readouts of all diagnostic trouble codes and make a note of them before disconnecting the battery or the EDU control module.
5 If communication between the ISAT and the EDU control module cannot be established, first check the leads between terminals 38 and 39 of the EDU control module and the data link connector (348). Also check the data link connector's power supply and ground and that the connector pins are undamaged.
6 When the contents of the system's trouble code memory have been transferred to the ISAT, fault diagnosis itself has been performed. The faults are now available in the form of 5-digit trouble codes and fault diagnosis can be continued in accordance with the fault diagnosis schedule for the system concerned.
7 However, start by entering the command codes that are applicable to the fault in question. Fault diagnosis may sometimes be facilitated by running through all command codes before starting detailed fault diagnosis under the relevant diagnostic trouble code.
8 To avoid all danger of damaging the EDU control module, always make sure that the ignition is switched off before unplugging the connector.
9 When carrying out fault diagnosis on the car's electronic systems, make a habit of checking first of all that the relevant electronic unit's ground connection is good and that all supply voltages are correct.
10 Unplug the connectors and check that the connections and pins are undamaged. Plug in the connectors again and clear all diagnostic trouble codes. Start the car and drive it to see whether there is a recurrence of the fault or faults.
11 Fault diagnosis can also be carried out using a Break Out Box and the ACC unit's test leads, part No.86 11 261.
12 When first detected, all diagnostic trouble codes are classified as permanent, i.e. the diagnostic trouble code begins with "4". If the fault disappears, the trouble code is classified as intermittent, i.e. the diagnostic trouble code begins with "2".
13 All signals round the 12v level are proportional to battery voltage and the readings should be regarded as guiding values only.
14 The 0v signals denote ground, but on a sensitive multimeter they may register slightly above 0v.
Clearing the memory
In the course of fault diagnosis the memory of the EDU control module may become corrupted and give rise to unusual fault symptoms.
To clear the memory, proceed as follows:
1 Switch off the ignition.
2 Remove and put back fuse 17 (+30) in the main fuse box on the passenger side of the dash board.
3 Switch on the ignition.
Faster EDU system turn-off
If the ignition is switched off by means of the ignition key, the EDU control module will continue to be supplied with current for five more minutes.
To turn off the EDU control module faster to carry out a test of some kind, remove fuse 17 (+30).
The aids currently available for fault diagnosis with the EDU system are as follows:
- Diagnostic trouble codes which in certain cases can identify the cause of the fault.
- Fault symptoms which enable the fault to be traced.
- Lamp and display tests which enable the display backlighting and all display segments to be lit for test purposes using an ISAT, Test Functions
Certain faults can cause the display to indicate "Err".