Component Tests and General Diagnostics

The following procedure applies to cars to 1987 inclusive and should be carried out if the ABS lamp lights while driving.

Note: First. Fault Descriptions

Special tools: Multimeter, P/N 9996525-3, or voltmeter, PIN 9996450-4, and ohmmeter, PIN 9999724-9.

General
These fault-tracing instructions assume that the braking system as a whole is operational.

Important
The instructions on this and the following pages must be observed at all times, otherwise the control module may be damaged.

Control module monitoring circuit
The control module incorporates a fault-monitoring circuit designed to detect faults in the module itself, and in the sensor circuitry, hydraulic modulator, signal circuits etc. On detecting a fault, the circuit disengages the ABS system and operates the warning lamp on the combined instrument. The following checks should be carried out if the lamp lights:

Note: All checks must be carried out.

1. Battery:
- do not disconnect battery while engine is running
- disconnect battery leads when booster charging
- do not use booster charger or voltage source higher than 16 V for jump starting




2. Ignition
- Switch off ignition when disconnecting or connecting control module connector.




3. Control module
- Remove control module, for example when stoving paint work. The module must not be exposed to temperatures above +80°C (176°F).
- Disconnect control module connector when carrying out arc welding on the car.
- Do not replace the module without checking the associated wiring and components, otherwise the new module may be damaged in the same manner as the original.

Checking fuses, connectors and ground terminals




4. Models to 1984 inclusive:
- Check fuses 2 and 10 in electrical distribution unit.
- Check fuse at right-hand wheel housing (80 A).

5. Models from 1985 to 1987 inclusive:
- Check fuses 2 and 12 in electrical distribution unit.

6. Check transient surge protector fuse (10 A)
- Remove cover over right-hand well in luggage compartment. Fold back carpet.

7. Check all ABS system connectors, wiring and ground terminals
- Ensure that components are correctly and securely connected.
- Poor contacts can cause fault symptoms.

Checking components and wiring
See appropriate wiring diagram.

8. Switch off ignition




9. Disconnect control module connector
- Depress catch and lift off connector.

10. Remove protective cover from hydraulic modulator




11. Remove protective cover from connector

Important: - Never insert test instrument probes into terminal sockets.
- Experience has shown that this may damage terminals and further aggravate fault(s).
- Check terminals through holes in connector sides.
- Do not exert greater force than necessary to make contact.
- Terminal numbers are punched in connector sides.

12. Check ground terminals in connector




13. Connect ohmmeter between ground and
- terminal 10
- terminal 20
- terminal 32
- terminal 34
- Resistance should be 0 ohm in all cases.
- If reading is incorrect: Check integrity and connection of leads.
- Leads are grounded at right-hand rear light.
- If test of terminal 32 indicates fault, repeat test with new valve relay. Relay is mounted on hydraulic modulator.



1.Valve relay
2.Motor relay
3.Connector

14. Switch on ignition




15. Check supply to transient surge protector
- Protector is mounted on bracket beside control module. Measure voltage at connector terminals 2, 4 and 3. Instrument should indicate 12 V in all cases. If no supply is present at terminal 3, check that leads are intact. If so, replace surge protector.




16. Check supply to converter unit (mounted beside surge protector)
- Measure voltage at all terminals. Instrument should indicate 12 V in all cases.
- If not: replace converter unit.

17. Check that wiring is intact

18. Check supply to control module connector

19. Connect voltmeter between ground and
- terminal 1
- terminal 7
- terminal 9
- terminal 25, while operating brake pedal
- terminal 27
- terminal 28
- terminal 29.
- Note, instrument should indicate 0.5 - 1.0 V. The instrument should indicate battery voltage in all cases except at terminal No.29.




20. If no voltage is present at
- terminal 1: Faulty surge protector
- terminal 7: Faulty converter unit
- terminal 9: Faulty converter unit
- terminal 25: Check brake light switch and replace if necessary. Also check brake light bulbs and replace if necessary.
- terminal 27: Faulty valve relay. Replace relay.
- terminal 28: Faulty motor relay. Replace relay.
- terminal 29: If correct voltage is present at terminal 27, instrument should indicate 0.5 - 1.0 V at terminal 29. If not, valve relay is faulty. Replace relay.

21. Check that wiring is intact




22. Switch off ignition




23. Check voltage at hydraulic modulator connector.
- Disconnect connector from unit




24. Switch on ignition




25. Connect voltmeter between ground and
- terminal 6
- terminal 7
- terminal 10
- terminal 12
- Instrument should indicate battery voltage in all cases.

26. If no voltage is present at
- terminal 6: Check fuse 2 in electrical distribution unit.
- terminal 7: Reconnect connector. ABS lamp should light. If not, replace lamp.
- terminal 10: Faulty surge protector. Replace unit.
- terminal 12: Check 80 A fuse at right front wheel housing.

27. Check that wiring is intact

28. Reinstall connector

29. Switch off ignition




30. Check front wheel sensors
- Connect ohmmeter to control module connector. Connect between terminals 4 and 6 for left front sensor, and between 21 and 23 for right front sensor. Instrument should indicate 0.9-2.2 kohm. If reading is incorrect: Measure at connectors at suspension strut towers in engine compartment. If wiring is intact and reading is still incorrect: Replace sensor.




31. Check rear sensor
- Connect ohmmeter between terminals 7 and 9. Instrument should indicate 0.6 - 1.6 kohm. If reading is incorrect: Measure at sensor connector located beside fuel filler pipe in luggage compartment. If reading is still incorrect, check first that wiring is intact.
- If wiring is intact and reading is still incorrect: Replace sensor.
Note, if clearance between sensor and sensor wheel is incorrect, system will become inoperative and ABS lamp will light. Clearance may be adjusted.




32. Checking sensor wiring
- Check that leads from control module connector are run to correct wheels. Connect ohmmeter to terminals indicated in illustration.
- Rotate left front, right front and rear wheels in turn, and connect probes to appropriate terminals. Resistance should vary as wheel rotates.




33. Check hydraulic modulator solenoid valves
- Connect one ohmmeter probe to terminal 32 on control module connector. Use other probe to measure at terminals 2 (left front), 35 (right front) and 18 (rear).
- Instrument should indicate 0.7-1.7 ohm in all cases. If reading is incorrect: Measure directly at hydraulic modulator (see wiring diagram). If reading is still incorrect: Replace modulator.




34. Switch on ignition




35. Check motor relay in hydraulic modulator
- Connect lead between ground and terminal 28.
- Hydraulic modulator should start.
- Note, do not connect lead for more than 2 seconds. If modulator does not start, repeat test with new motor relay.

36. Check that wiring is intact




37. Check valve relay in hydraulic modulator
- Connect voltmeter between terminal 32 and ground.
- Connect lead between ground and terminal 27.
- Valve relay should operate and instrument should indicate battery voltage.
- If fault persists, repeat test with new relay.

38. Check that wiring is intact

39. Switch off ignition and disconnect test equipment
- If no fault has been detected, repeat procedure with new control module.

40. Reinstall panels, carpets, hydraulic modulator cover etc.