Storage of Fault Codes

The diagnostic system monitors both long-term and intermittent faults in the ABS system. If a fault is detected, the ANTI-LOCK warning lamp will illuminate and will remain lit until the ignition is turned off, at which time the fault code will be stored into memory. If the fault self-corrects while driving, the warning lamp will remain lit until the ignition is switched off. If the fault is still absent when the ignition is switched on again, the warning lamp will not light. If the fault is still present, the warning lamp will light again. Any fault code that may be stored in memory will not be erased even if the battery is disconnected or the ECU is disconnected from the vehicle. Faults are stored according to their priority. Valve faults have the highest priority while intermittent faults that occur at speeds below 25 mph have the lowest priority. Such low speed intermiftent faults will be erased automatically if they are not repeated within 14 cycles of the ignition switch.

Fault Code Retrieval In order to access the stored codes within the ABS system, a two-pole diagnostic plug has been added to the cars' wiring harness. On 1990 900 models, the plug is located behind the coolant reservoir in the engine compartment. For 1991, the plug has been relocated under the rear seat, adjacent to the ABS ECU connector. On all 9000 models (1990-), the plug is located near the ABS ECU where the main wiring harness passes through the false bulkhead (Figure 1).

Parts Required To perform the read-out process via the ANTI-LOCK warning lamp, switched jumper lead, P/N 83 93 886, should be attached to the diagnostic plug. An adapter for the jumper lead can be made using a spare twopole connector housing, P/N 95 18 713, two male terminals, P/N 95 52 100, and suitable lengths of wire.