Anti-Lock Brake System/traction Control Audi Cabriolet I

DESCRIPTION

Note. 1995 Bosch 5 ABS system may not have all functions of 1996 version. Some testing procedures are not necessary for 1995 models.

Bosch 5 Anti-lock Brake System (ABS) for 1996 can be optionally equipped with Traction Control System (TCS) and Electronic Differential Lock (EDL) which all operate using the ABS system. ABS consists of an ABS control module, hydraulic unit, relays, wheel speed sensors and necessary wiring, in addition to the basic braking system. The brake pressure regulator has been deleted, as it's function has been replaced by ABS control module programming.

When brake pedal is applied, the ABS control module monitors input signals from each wheel speed sensor. If control module senses wheel lock-up, it will output a signal to appropriate solenoid valve. Each solenoid valve allows hydraulic pressure to increase or decrease to the appropriate brake caliper.

ELECTRONIC DIFFERENTIAL LOCK

Electronic Differential Lock (EDL) prevents wheel spin to drive wheel during hard acceleration. EDL operates up to a speed of 25 MPH. If brake temperatures are high, ABS control module will reduce or cancel EDL operation until brake temperatures are reduced.

TRACTION CONTROL SYSTEM

Traction Control System (TCS) prevents wheels from spinning or slipping during driving or acceleration on slippery surfaces. When wheel slip or spin is detected by ABS control module, commands are sent to engine control system to reduce engine power. TCS is effective at any speed.

ABS CONTROL MODULE

ABS control module controls ABS, EDL and TCS functions. Some TCS functions are also controlled by Engine Control Module (ECM). If a fault occurs in the engine control or other system affecting TCS operation, ABS control module may abort ABS operation, EDL or TCS functions. By monitoring warning lights, system at fault may be determined.

ABS control module has self-diagnostic capabilities. Using VAG 1551 tester, Diagnostic Trouble Codes (DTCs) can be retrieved. No provision was made for warning light flash code output.

If vehicle is equipped with traction control system and ABS control module is to be replaced, the new control module coding must match vehicle application. Using VAG 1551 tester, check control module identification. Manual transmission vehicles use control module I.D. 000. Automatic transmission vehicles use control module I.D. 001. If incorrect I.D. is displayed on scan tester, correct as necessary.

BRAKE FLUID

Replace brake fluid every 2 years regardless of mileage. Bleed system until fluid flows clear. See BLEEDING BRAKE SYSTEM . Use only DOT 4 brake fluid that meets SAE specification J1703. Do not use DOT 5 silicone brake fluid. Dispose of used fluid properly.

BLEEDING BRAKE SYSTEM

Note. Manufacturer recommends bleeding brake system using pressure brake bleeder. Follow tool manufacturer's instructions.

If pressure bleeding equipment is not available, Using an extractor bulb, remove fluid from reservoir. Refill reservoir with fresh fluid. Pump brake pedal and open bleeder screw. Bleed brakes in sequence as follows; right/rear, left/rear, right/front left/front. Also bleed clutch cylinder (if equipped) after bleeding brakes.

WARNING LIGHTS

ABS and traction control systems conduct a self-test after ignition is turn on. The Yellow ABS warning light comes on during self-test. The traction control indicator also will come on during self-test of traction control system (if equipped). During self-test noises may be heard from return pump and relays, also a vibration may be felt from brake pedal. After approximately 4 seconds or less, warning lights should go off indicating system passed self-test. If ABS system fails self-test, the ABS warning light will come on. If a fault occurs in the traction control system that affects the ABS system, both traction control and ABS waring lights will come on. Either warning light may stay on or sporadically go on and off depending on type of failure (hard or intermittent fault). In any case when warning lights come on after self-test, check system for Diagnostic Trouble Codes (DTCs).

PRELIMINARY CHECKS

1. Ensure all wheels and tires are of approved size (all 4 identical) and tires are properly inflated.
2. Conventional brake system in proper working order and stoplight switch is operational.
3. Brake fluid must be at proper level and no hydraulic lines leaking.
4. Check wheel bearing play and condition. Correct as necessary.
5. Check wheel speed sensor mounting and build-up of dirt etc.
6. Check condition of all fuses.
7. Battery voltage must be at least 10.5 volts.
8. Ensure ABS control module harness connector is securely connected and is not corroded or damaged.

EQUIPMENT HOOK-UP

1. To retrieve DTCs from ABS and traction control system, VAG 1551 scan tool along with appropriate data cable is required. No provision for flash codes is designed into system.
2. DLC is located in auxiliary relay panel No. 1 on left side of plenum chamber. Connect data cable to Black DLC.
3. If scan tester display does not operate, check data cable connection. Also check for battery power at DLC. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . If scan tester display operates, select RAPID DATA TRANSFER and select BRAKE ELECTRONICS. If NO SIGNAL FROM CONTROL MODULE or ERROR IN COMMUNICATION LINK is displayed on scan tool, fault may exist in data cable or DLC circuits. If data communications are okay, control module identification will appear. For additional information see «ABS CONTROL MODULE»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__abs-control-module) under OPERATION. System is now ready for diagnostic testing.

RETRIEVING DTCs

1. Connect VAG 1551 scan tool. See «EQUIPMENT HOOK-UP»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__equipment-hook-up) . Turn ignition on. Access SELECT FUNCTION menu selection screen. Enter 02 to select CHECK DTC MEMORY. Press "Q" key to confirm input.
2. If NO DTC RECOGNIZED message is displayed on scan tool, enter 06 END OUTPUT. If any DTCs are displayed, print out or write down DTC in order they are output. Proceed to applicable DTC test and perform repair. After repair is complete, clear DTCs and recheck DTCs to ensure fault is repaired. See «CLEARING»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__clearing-dtcs) DTCs.

CLEARING DTCs

Note. DTCs must be output before attempting to clear DTCs. DTCs will not clear if vehicle is driven over 13 MPH (20 km/h) or ignition is turned off between retrieving DTCs and clearing DTCs.

1. With scan tool connected and ignition on, access SELECT FUNCTION menu selection screen. Enter 05 to select ERASE DTC MEMORY. Press "Q" key to confirm input.
2. Turn ignition off. Disconnect scan tool data cable from DLC. Turn ignition on. Verify ABS (and TCS if equipped) warning light goes out 2-4 seconds after ignition is turned on. Road test vehicle to ensure warning lights do not come on during road test. If ABS, TCS or EDL warning lights come on during test drive, repeat diagnostic procedure.

DTC TESTING

DTC DEFINITIONS

DTC 00000: NO FAULT DETECTED

If DTC 00000 is displayed from scan tool along with ABS or TCS warning light(s) on, check for ABS control module supply voltage less than 10.5 volts at a speed of less than 4 MPH (6 km/h). See WIRING DIAGRAMS . If no electrical fault is detected, a mechanical fault (such as a stuck solenoid) may be causing warning light to come on. See CIRCUIT TEST .

DTC 00257: LEFT/FRONT INLET VALVE CIRCUIT

Fault may be caused by faulty left/front inlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform steps 1) and 13) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00259: RIGHT/FRONT INLET VALVE CIRCUIT

Fault may be caused by faulty right/front inlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform steps 2) and 14) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00265: LEFT/FRONT OUTLET VALVE CIRCUIT

Fault may be caused by faulty left/front outlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform step 1) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00267: RIGHT/FRONT OUTLET VALVE CIRCUIT

Fault may be caused by faulty right/front outlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform step 2) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00273: RIGHT/REAR INLET VALVE CIRCUIT

Fault may be caused by faulty right/rear inlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform steps 4) and 16) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00274: LEFT/REAR INLET VALVE CIRCUIT

Fault may be caused by faulty left/rear inlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform steps 3) and 15) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00275: RIGHT/REAR OUTLET VALVE CIRCUIT

Fault may be caused by faulty right/rear outlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform step 4) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still cannot be located, replace ABS control module with known good unit.

DTC 00276: LEFT/REAR OUTLET VALVE CIRCUIT

Fault may be caused by faulty left/rear outlet valve, open or short in wiring between ABS hydraulic unit and ABS control module. Perform step 3) of CIRCUIT TEST . If malfunction cannot be pinpointed during circuit testing, check all wiring and harness connectors for poor contact corrosion etc. If fault still exists, substitute known good control module and recheck for symptom and DTC.

DTC 00283: LEFT/FRONT WHEEL SPEED SENSOR

1. Fault may be caused by the following; Left/front wheel speed sensor or speed sensor rotor is dirty or damaged. Left/front wheel speed sensor not properly installed. Excessive wheel bearing play. Faulty wheel speed sensor. Open or short in wiring between wheel speed sensor and ABS control module. Incorrect ABS control module identification.
2. Perform a visual check on the above items. If inspection is inconclusive, check wheel speed sensor function. Using VAG 1551 scan tool, select function 08 - READ MEASURING VALUE BLOCK. Select DISPLAY GROUP 001. Drive vehicle to ensure all wheel speeds are within one km/h difference of each other. Raise and support vehicle. Check wheel speed value while rotating each wheel one at a time.
3. Perform step 7) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If fault remains after performing circuit test, check wiring harness and connectors for poor contact and corrosion etc. If okay, check ABS control module identification. See «ABS CONTROL MODULE»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__abs-control-module) . If fault still exists, substitute known good control module and recheck for symptom and DTC.

DTC 00285: RIGHT/FRONT WHEEL SPEED SENSOR

1. Fault may be caused by the following; Right/front wheel speed sensor or speed sensor rotor is dirty or damaged. Right/front wheel speed sensor not properly installed. Excessive wheel bearing play. Faulty wheel speed sensor. Open or short in wiring between wheel speed sensor and ABS control module. Incorrect ABS control module identification.
2. Perform a visual check on the above items. If inspection is inconclusive, check wheel speed sensor function. Using VAG 1551 scan tool, select function 08 - READ MEASURING VALUE BLOCK. Select DISPLAY GROUP 001. Drive vehicle to ensure all wheel speeds are within one km/h difference of each other. Raise and support vehicle. Check wheel speed value while rotating each wheel one at a time.
3. Perform step 8) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If fault remains after performing circuit test, check wiring harness and connectors for poor contact and corrosion etc. If okay, check ABS control module identification. See «ABS CONTROL MODULE»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__abs-control-module) . If fault still exists, substitute known good control module and recheck for symptom and DTC.

DTC 00287: RIGHT/REAR WHEEL SPEED SENSOR

1. Fault may be caused by the following; Right/rear wheel speed sensor or speed sensor rotor is dirty or damaged. Right/rear wheel speed sensor not properly installed. Excessive wheel bearing play. Faulty wheel speed sensor. Open or short in wiring between wheel speed sensor and ABS control module. Incorrect ABS control module identification.
2. Perform a visual check on the above items. If inspection is inconclusive, check wheel speed sensor function. Using VAG 1551 scan tool, select function 08 - READ MEASURING VALUE BLOCK. Select DISPLAY GROUP 001. Drive vehicle to ensure all wheel speeds are within one km/h difference of each other. Raise and support vehicle. Check wheel speed value while rotating each wheel one at a time.
3. Perform step 10) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If fault remains after performing circuit test, check wiring harness and connectors for poor contact and corrosion etc. If okay, check ABS control module identification. See «ABS CONTROL MODULE»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__abs-control-module) . If fault still exists, substitute known good control module and recheck for symptom and DTC.

DTC 00290: LEFT/REAR WHEEL SPEED SENSOR

1. Fault may be caused by the following; Left/rear wheel speed sensor or speed sensor rotor is dirty or damaged. Left/rear wheel speed sensor not properly installed. Excessive wheel bearing play. Faulty wheel speed sensor. Open or short in wiring between wheel speed sensor and ABS control module. Incorrect ABS control module identification.
2. Perform a visual check on the above items. If inspection is inconclusive, check wheel speed sensor function. Using VAG 1551 scan tool, select function 08 - READ MEASURING VALUE BLOCK. Select DISPLAY GROUP 001. Drive vehicle to ensure all wheel speeds are within one km/h difference of each other. Raise and support vehicle. Check wheel speed value while rotating each wheel one at a time.
3. Perform step 9) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If fault remains after performing circuit test, check wiring harness and connectors for poor contact and corrosion etc. If okay, check ABS control module identification. See «ABS CONTROL MODULE»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__abs-control-module) . If fault still exists, substitute known good control module and recheck for symptom and DTC.

DTC 00301: RETURN FLOW PUMP

1. Fault may be caused by the following; Open or high resistance in power or ground circuit to return flow pump. Open or short in circuit between return flow pump relay and ABS control module. Faulty ABS return flow pump relay. Faulty return flow pump. Faulty hydraulic unit
2. Check power and ground circuit to return flow pump for open and short to ground. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair circuit if necessary.
3. Check circuits between ABS return flow pump relay and ABS control module for open short to ground and short to power. Repair if necessary.
4. To test ABS return flow pump relay, ABS return flow pump and hydraulic unit perform steps 12) and 17) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . Confirm operation by checking measuring value block display field 07 with VAG 1551.

DTC 00302: ABS SOLENOID VALVE RELAY

1. Fault may be caused by the following; Faulty connection or excessive resistance in ground circuit to ABS solenoid valve relay. Open circuit, short to ground or short to battery power in circuits between ABS solenoid valve relay and ABS control module. Faulty ABS solenoid valve relay. Faulty hydraulic unit.
2. Check circuits between ABS solenoid valve relay and ABS control module for open circuit, short to ground or short to battery power. Repair if necessary. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) .
3. Test ABS solenoid valve relay and ABS hydraulic unit. Perform steps 11) and 13) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . Confirm operation by checking measuring value block display field 08 with VAG 1551.

DTC 00526: STOPLIGHT SWITCH

1. DTC 00526 indicates ABS control module is not receiving a stoplight switch signal. Fault may be caused by the following; Both stoplight bulbs out. Open circuit or short to ground in stoplight circuit. Faulty stoplight switch Faulty ABS control module.
2. Ensure stoplight bulbs are okay. Check stoplight switch operation by checking measuring value block display field 05 with VAG 1551. Check stoplight circuit for open or short to ground. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) .

DTC 00529: RPM SIGNAL MISSING

Note. DTC 00529 applies only to models equipped with traction control system.

1. Fault may be caused by the following; Open circuit, short to ground or short to battery voltage in circuits between ABS control module and Engine Control Module (ECM). Faulty ECM. Faulty ABS control module.
2. Check for open or short in circuits between ABS control module and ECM. If tachometer on instrument panel is inoperative and no fault can be found in circuits between ECM and ABS control module, substitute a known good ECM and recheck for symptom and DTC.

DTC 00532: SUPPLY VOLTAGE

1. Fault is stored when vehicle is traveling more than 4 MPH (6 km/h) and voltage to ABS control module drops below acceptable range (10.5 volts). If voltage returns to within range, ABS indicator lamp will go out and ABS will return to operation.
2. Check battery condition and charging system operation. Check for voltage drops in power supply circuits. Check terminals to ABS control module for damage and corrosion. Repair as necessary.

DTC 00597: VARYING WHEEL SPEED IMPULSE

1. Fault may be caused by the following; Wheel speed sensor or speed sensor rotor is dirty or damaged. Wheel speed sensor not properly installed. Excessive wheel bearing play. Wheels and/or tires not all same size.
2. Perform a visual check on the above items. If inspection is inconclusive, perform steps 7) through 10) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) .
3. Check wheel speed sensor function. Using VAG 1551 scan tool, select function 08 - READ MEASURING VALUE BLOCK. Select DISPLAY GROUP 001. Drive vehicle to ensure all wheel speeds are within one km/h difference of each other. Raise and support vehicle. Check wheel speed value while rotating each wheel one at a time.

DTC 00623: ABS/TRANSMISSION ELECTRICAL CONNECTION

Note. DTC 00623 applies only to models equipped with automatic transmission and traction control system.

DTC 00623 indicates open or short to ground in circuit between ABS control module and transmission control module. Check and repair circuit as necessary. See WIRING DIAGRAMS . If vehicle is not equipped with automatic transmission and DTC 00623 is displayed, ABS control module is incorrectly coded. See ABS CONTROL MODULE .

DTC 00642: RIGHT/FRONT EDL SWITCH-OVER VALVE

Note. DTC 00642 applies only to models with Electronic Differential Lock (EDL).

1. Fault may be caused by the following; Open, short to voltage, or short to ground in the circuits between ABS control module and hydraulic unit. Faulty right/front traction control switch-over valve.
2. Perform steps 5) and 18) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If circuit test is inconclusive, ensure related wiring and harness connectors are in good condition. If fault still exists, substitute ABS control module with known good unit. Recheck for symptom and DTC.

DTC 00643: RIGHT/FRONT EDL OUTLET VALVE

Note. DTC 00643 applies only to models with Electronic Differential Lock (EDL).

1. Fault may be caused by the following; Open, short to voltage, or short to ground in the circuits between ABS control module and hydraulic unit. Faulty right/front traction control outlet valve.
2. Perform steps 6) and 18) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If circuit test is inconclusive, ensure related wiring and harness connectors are in good condition. If fault still exists, substitute ABS control module with known good unit. Recheck for symptom and DTC.

DTC 00644: LEFT/FRONT EDL SWITCH-OVER VALVE

Note. DTC 00644 applies only to models with Electronic Differential Lock (EDL).

1. Fault may be caused by the following; Open, short to voltage, or short to ground in the circuits between ABS control module and hydraulic unit. Faulty left/front traction control switch-over valve.
2. Perform steps 5) and 17) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If circuit test is inconclusive, ensure related wiring and harness connectors are in good condition. If fault still exists, substitute ABS control module with known good unit. Recheck for symptom and DTC.

DTC 00645: LEFT/FRONT EDL OUTLET VALVE

Note. DTC 00645 applies only to models with Electronic Differential Lock (EDL).

1. Fault may be caused by the following; Open, short to voltage, or short to ground in the circuits between ABS control module and hydraulic unit. Faulty left/front traction control outlet valve.
2. Perform steps 6) and 17) of «CIRCUIT TEST»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__circuit-tests) . If circuit test is inconclusive, ensure related wiring and harness connectors are in good condition. If fault still exists, substitute ABS control module with known good unit. Recheck for symptom and DTC.

DTC 00646: ABS MOTOR ELECTRICAL CONNECTION NO. 1

Note. DTC 00646 applies only to models with Traction Control System (TCS).

1. Fault may be caused by the following; Open circuit, short to ground or short to battery voltage in circuits between ABS control module and Engine Control Module (ECM). Faulty ECM. Faulty ABS control module.
2. Check for open or short in circuits between ABS control module and ECM. If no faults can be located in circuits between ECM and ABS control module, substitute a known good ECM and recheck for symptom and DTC.

DTC 00647: ABS MOTOR ELECTRICAL CONNECTION NO. 2

Note. DTC 00647 applies only to models with Traction Control System (TCS).

1. Fault may be caused by the following; Open circuit, short to ground or short to battery voltage in circuits between ABS control module and Engine Control Module (ECM). Faulty ECM. Faulty ABS control module.
2. Check for open or short in circuits between ABS control module and ECM. If no faults can be located in circuits between ECM and ABS control module, substitute a known good ECM and recheck for symptom and DTC.

DTC 00668: ABS CONTROL MODULE KEEP ALIVE POWER

Fault is due to open or short to ground in ABS control module terminal No. 50 circuit (hot at all times). Repair circuit as necessary. See WIRING DIAGRAMS .

DTC 00761: DTC STORED IN ECM

Note. DTC 00761 applies only to models with Traction Control System (TCS).

DTC 00761 indicates a malfunction is stored in Engine Control Module (ECM) that may affect Traction Control System (TCS) operation. ECM reduces engine torque during TCS operation. Service engine control system as necessary. See self-diagnostics in TESTS W/CODES article in ENGINE PERFORMANCE Section.

DTC 65535: CONTROL MODULE FAULT

Fault is caused by ABS control module internal failure. Replace ABS control module. Recheck for symptom and DTC.

Scheme 9

Scheme 10

CIRCUIT TESTS

Note. To avoid damage to ABS harness connector pins, manufacturer recommends using VAG 1598/20 Test Box (breakout box) to carry out measurements. Terminal number designations on Test Box (VAG 1598/20) are identical to ABS control module harness connector terminals.

1. Left/Front Inlet & Outlet Valves Measure resistance between Test Box (VAG 1598/20) terminals No. 5 and 33. Resistance should be 9-22 ohms. If resistance is not within specification, check inlet and out valve circuits in wiring harness between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace hydraulic unit.
2. Right/Front Inlet & Outlet Valves Measure resistance between Test Box (VAG 1598/20) terminals No. 54 and 26. Resistance should be 9-22 ohms. If resistance is not within specification, check inlet and out valve circuits in wiring harness between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace hydraulic unit.
3. Left/Rear Inlet & Outlet Valves Measure resistance between Test Box (VAG 1598/20) terminals No. 53 and 25. Resistance should be 9-22 ohms. If resistance is not within specification, check inlet and out valve circuits in wiring harness between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace hydraulic unit.
4. Right/Front Inlet & Outlet Valves Measure resistance between Test Box (VAG 1598/20) terminals No. 6 and 34. Resistance should be 9-22 ohms. If resistance is not within specification, check inlet and out valve circuits in wiring harness between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace hydraulic unit.
5. Left/Front TCS Switch-Over Valve Measure resistance between Test Box (VAG 1598/20) terminals No. 3 and 55. Resistance should be 12-28 ohms. If resistance is not within specification, check inlet and out valve circuits in wiring harness between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace hydraulic unit.
6. Left/Front & Right/Front TCS Outlet Valves Measure resistance between Test Box (VAG 1598/20) terminals No. 4 and 27. Resistance should be 12-28 ohms. If resistance is not within specification, check inlet and out valve circuits in wiring harness between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace hydraulic unit.
7. Left/Front Wheel Speed Sensor Measure resistance between specified Test Box (VAG 1598/20) terminals. See «TEST TERMINAL IDENTIFICATION»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control) table. Resistance should be 400-2300 ohms. If resistance is not within specification, check wheel speed sensor harness circuit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace suspect wheel speed sensor. TEST TERMINAL IDENTIFICATION Application Terminals No. Front Wheel Drive W/O TCS & EDL 10 & 36 Front Wheel Drive With EDL 9 & 10 Front Wheel Drive With EDL & TCS 9 & 10
8. Right/Front Wheel Speed Sensor Measure resistance between Test Box (VAG 1598/20) terminals No. 14 and 15 (14 and 42 on models with TCS). Resistance should be 400-2300 ohms. If resistance is not within specification, check wheel speed sensor harness circuit for open, short to ground and short to power. Also check harness connector at suspect wheel speed sensor. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace suspect wheel speed sensor.
9. Left/Rear Wheel Speed Sensor Measure resistance between Test Box (VAG 1598/20) terminals No. 12 and 13. Resistance should be 400-2300 ohms. If resistance is not within specification, check wheel speed sensor harness circuit for open, short to ground and short to power. Also check harness connector at suspect wheel speed sensor. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace suspect wheel speed sensor.
10. Right/Rear Wheel Speed Sensor Measure resistance between Test Box (VAG 1598/20) terminals No. 12 and 13. Resistance should be 400-2300 ohms. If resistance is not within specification, check wheel speed sensor harness circuit for open, short to ground and short to power. Also check harness connector at suspect wheel speed sensor. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace suspect wheel speed sensor.
11. ABS Solenoid Valve Relay Measure resistance between Test Box (VAG 1598/20) terminals No. 2 and 37. Resistance should be 30-80 ohms. If resistance is not within specification, check relay circuits between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace ABS solenoid valve relay.
12. ABS Return Flow Pump Relay Measure resistance between Test Box (VAG 1598/20) terminals No. 2 and 7. Resistance should be 30-80 ohms. If resistance is not within specification, check relay circuits between ABS control module and hydraulic unit for open, short to ground and short to power. See «WIRING DIAGRAMS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__wiring-diagrams) . Repair if necessary. If wiring is okay, replace ABS return flow pump relay.
13. Left/Front ABS Inlet Valve Raise support vehicle. Turn ignition on. Connect a jumper wire between Test Box (VAG 1598/20) terminals No. 1 and 2. Connect another jumper wire between terminals No. 26 and 37. Connect a third jumper wire between terminals No. 5 and 28. Have an assistant depress and hold brake pedal. Turn left/front wheel by hand. If left/front brake locks, attempt to turn another wheel. If another wheel can be turned, hydraulic brake lines are improperly routed. If all brakes lock, replace faulty left/front inlet valve. Disconnect jumper wires. Left/front brake should now lock.
14. Right/Front ABS Inlet Valve Raise support vehicle. Turn ignition on. Connect a jumper wire between Test Box (VAG 1598/20) terminals No. 1 and 2. Connect another jumper wire between terminals No. 28 and 37. Connect a third jumper wire between terminals No. 54 and 28. Have an assistant depress and hold brake pedal. Turn right/front wheel by hand. If right/front brake locks, attempt to turn another wheel. If another wheel can be turned, hydraulic brake lines are improperly routed. If all brakes lock, replace faulty right/front inlet valve. Disconnect jumper wires. right/front brake should now lock.
15. Left/Rear ABS Inlet Valve Raise support vehicle. Turn ignition on. Connect a jumper wire between Test Box (VAG 1598/20) terminals No. 1 and 2. Connect another jumper wire between terminals No. 28 and 37. Connect a third jumper wire between terminals No. 53 and 28. Have an assistant depress and hold brake pedal. Turn left/rear wheel by hand. If left/rear brake locks, attempt to turn another wheel. If another wheel can be turned, hydraulic brake lines are improperly routed. If all brakes lock, replace faulty left/rear inlet valve. Disconnect jumper wires. left/rear brake should now lock.
16. Right/Rear ABS Inlet Valve Raise support vehicle. Turn ignition on. Connect a jumper wire between Test Box (VAG 1598/20) terminals No. 1 and 2. Connect another jumper wire between terminals No. 28 and 37. Connect a third jumper wire between terminals No. 6 and 28. Have an assistant depress and hold brake pedal. Turn right/rear wheel by hand. If right/rear brake locks, attempt to turn another wheel. If another wheel can be turned, hydraulic brake lines are improperly routed. If all brakes lock, replace faulty right/rear inlet valve. Disconnect jumper wires. right/rear brake should now lock. NOTE: Steps 17) and 18) apply only to models equipped with Electronic Differential Lock (EDL).
17. Return Flow Pump, Left/Front TCS Switchover & Outlet Valves, Pressure limiting Valve, Left/Front ABS Outlet Valve & Right/Rear ABS Outlet Valve Connect a jumper wire between Test Box (VAG 1598/20) terminals No. 1 and 2. Connect another jumper wire between terminals No. 7 and 37. Connect a third jumper wire between terminals No. 37 and 28. Connect a brake pressure gauge to left/front brake caliper. Bleed air from caliper. Connect a fourth jumper wire between terminals No. 3 and 28. Turn ignition on, then after not more than 10 seconds turn ignition off. When ignition is on, return flow pump should run. Pressure gauge should indicate a maximum pressure of 72.5 PSI (5 Bar). Connect another jumper wire between terminals No. 4 and 28. Turn ignition on, then after not more than 10 seconds turn ignition off. When ignition is on, outlet valve should operate and gauge pressure should increase to 2100-2825 PSI (145-195 BAR). If pressure is not as specified, replace ABS hydraulic unit.
18. Return Flow Pump, Right/Front TCS Switchover & Outlet Valves, Pressure limiting Valve, Right/Front ABS Outlet Valve & Left/Rear ABS Outlet Valve Connect a jumper wire between Test Box (VAG 1598/20) terminals No. 1 and 2. Connect another jumper wire between terminals No. 7 and 37. Connect a third jumper wire between terminals No. 37 and 28. Connect a brake pressure gauge to left/front brake caliper. Bleed air from caliper. Connect a fourth jumper wire between terminals No. 55 and 28. Turn ignition on, then after not more than 10 seconds turn ignition off. When ignition is on, return flow pump should run. Pressure gauge should indicate a maximum pressure of 72.5 PSI (5 Bar). Connect another jumper wire between terminals No. 27 and 28. Turn ignition on, then after not more than 10 seconds turn ignition off. When ignition is on, outlet valve should operate and gauge pressure should increase to 2100-2825 PSI (145-195 BAR). If pressure is not as specified, replace ABS hydraulic unit.

Removal

Disconnect negative battery cable. Disconnect electrical connector from hydraulic unit. Disconnect all brake lines from hydraulic unit. Remove relay cover and relays. Remove mounting bolts and hydraulic unit. (Scheme 11), or 5.

Installation

To install, reverse removal procedure. Ensure correct version hydraulic unit is installed. Tighten bolts to specification and Bleed entire brake system. See the following

1. «TORQUE SPECIFICATIONS»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__torque-specifications) .
2. «BLEEDING BRAKE SYSTEM»(/audi/cabriolet/i-1991-2000/remont/anti-locktraction-control/#anti-lock-brake-systemtraction-control__bleeding-brake-system) .

Scheme 11

Scheme 12

Removal & Installation

Raise and support vehicle. Remove Wheel(s). Disconnect and detach wheel speed sensor wire harness. Pull sensor from rear axle or front knuckle. Clean and lubricate sensor mounting area. To install, use NEW sensor mounting sleeve. Push in pre-lubricated sensor by hand until fully inserted. Reconnect and secure wiring harness.

ADJUSTMENTS

See ADJUSTMENTS in BRAKE SYSTEM article.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

WIRING DIAGRAMS

For wiring, see ANTI-LOCK BRAKE SYSTEM article.

See also:
• BRAKE SYSTEM
• ANTI-LOCK BRAKE SYSTEM
• BLEEDING BRAKE SYSTEM
• WIRING DIAGRAMS
• ABS CONTROL MODULE
• EQUIPMENT HOOK-UP
• CLEARING
• DTC 00000
• DTC 00257
• DTC 00259
• DTC 00265
• DTC 00267
• DTC 00273
• DTC 00274
• DTC 00275
• DTC 00276
• DTC 00283
• DTC 00285
• DTC 00287
• DTC 00290
• DTC 00301
• DTC 00302
• DTC 00526
• DTC 00529
• DTC 00532
• DTC 00597
• DTC 00623
• DTC 00642
• DTC 00643
• DTC 00644
• DTC 00645
• DTC 00646
• DTC 00647
• DTC 00668
• DTC 00761
• DTC 65535
• CIRCUIT TEST
• TEST TERMINAL IDENTIFICATION
• TORQUE SPECIFICATIONS