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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  . 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  . 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  . 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  . 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  . 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  . 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  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  . 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  . 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  . 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  . 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  . 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  . 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.
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