Buick Regal Owners & Service Manuals

Buick Regal: Rear Wiper System Malfunction

Diagnostic Instructions

  • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
  • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
  • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Wipers and Washers

1. Rear Wiper Inoperative.
2. Rear Wiper Always ON.

Circuit/System Description

The rear wiper motor is controlled by the body control module (BCM) via a printed circuit board (PCB) relay. The BCM will respond by commanding the specific rear wiper function based on an input from the rear wiper switch, which is part of the windshield wiper/washer switch. The rear wiper switch uses a resistor ladder to determine low speed, intermittent, and rear washer operation. A constant B+ and ground are supplied to the rear wiper motor. When the rear wiper switch is placed in the low speed, intermittent, or rear washer position, the voltage is pulled down through a different resistor in the resistor ladder, reducing the voltage seen at the BCM.

The BCM monitors the liftgate ajar signal circuit, and the BCM will disable the function of the rear wiper motor if the liftgate or liftglass is ajar or open

Diagnostic Aids

If the vehicle is a HATCHBACK, The rear liftgate must be closed in order for the rear wiper to work. The liftgate ajar switch signal circuit provides information to the rear window wiper module about the status of the liftgate. If the liftgate or liftglass is open the rear wiper operation is not performed.

Reference Information

Schematic Reference

Wiper/Washer Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Wiper/Washer System Description and Operation

Electrical Information Reference

  • Circuit Testing
  • Connector Repairs
  • Testing for Intermittent Conditions and Poor Connections
  • Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON.

2. Verify the scan tool Rear Closure Ajar Switch parameter changes between Inactive and Active when opening and closing the liftgate.

  • If the parameter does not change

Refer to Rear Hatch/Gate Ajar Indicator Malfunction (With TB5) Rear Hatch/Gate Ajar Indicator Malfunction (Without TB5)

  • Go to next step: If the parameter changes

3. Verify that DTC B370B is not set.

  • If DTC B370B is set

Refer to DTC B370B

  • Go to next step: If DTC B370B is not set

4. Verify the scan tool Rear Wiper Switch parameter changes between Off and On when turning the rear wipers ON and OFF.

  • If the parameter does not change

Refer to Circuit/System Testing - Rear Wiper/Washer Switch Malfunction.

  • Go to next step: If the parameter changes

5. Verify the Rear Wiper Motor turns On when commanding the Rear Wiper Active with a scan tool.

  • If the Rear Wiper Motor does not turn ON

Refer to Circuit/System Testing - Rear Wiper Motor Malfunction

  • Go to next step: If the Rear Wiper Motor turns ON

6. All OK.

Circuit/System Testing

Rear Wiper/Washer Switch Malfunction

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S82 Windshield Wiper/Washer Switch. It may take up to 11 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 1 and ground.

  • If 10 Ω or greater
  1. Ignition OFF.
  2. Test for less than 2 Ω in the low reference circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, replace the K9 Body Control Module.
  • Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for greater than 8 V between the signal circuit terminal 5 and ground.

  • If less than 8 V
  1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
  2. Test for infinite resistance between the signal circuit and ground
    • If less than infinite resistance, repair the short to ground on the circuit.
    • Go to next step: If infinite resistance
  3. Test for less than 2 Ω in the signal circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, replace the K9 Body Control Module.

Go to next step: If 8 V or greater

5. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module, ignition ON.

6. Test for less than 1 V between the S82 Windshield Wiper/Washer Switch signal circuit terminal 5 and ground.

  • If 1 V or greater

Repair the short to voltage on the circuit.

  • Go to next step: If less than 1 V

7. Test or replace the S82 Windshield Wiper/Washer Switch.

Rear Wiper Motor Malfunction

1. Ignition OFF, and all vehicle systems OFF. Disconnect the X1 harness connector at the X50A Fuse Block - Underhood. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the X50A Fuse Block - Underhood ground circuit terminal 53 and ground.

  • If 10 Ω or greater
  1. Test for less than 2 Ω in the ground circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, repair the open/high resistance in the ground connection.
  • Go to next step: If less than 10 Ω

3. Disconnect the harness connector at the M45 Rear Wiper Motor and connect the X1 harness connector at the X50A Fuse Block - Underhood. It may take up to 2 min for all vehicle systems to power down.

4. Test for less than 10 Ω between the ground circuit terminal B and ground.

  • If 10 Ω or greater
  1. Test for less than 2 Ω in the ground circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, repair the open/high resistance in the ground connection.
  • Go to next step: If less than 10 Ω

5. Ignition ON.

6. Verify a test lamp illuminates between the ignition circuit terminal C and ground.

  • If the test lamp does not illuminate and the circuit fuse is good
  1. Ignition OFF.
  2. Test for less than 2 Ω in the ignition circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, refer to Retained Accessory Power Malfunction.
  • If the test lamp does not illuminate and the circuit fuse is open
  1. Ignition OFF, disconnect the M45 Rear Wiper Motor.
  2. Test for infinite resistance between the ignition circuit and ground.
    • If less than infinite resistance, repair the short to ground on the circuit.
    • If infinite resistance, replace the M45 Rear Wiper Motor.
  • Go to next step: If the test lamp illuminates

7. Verify a test lamp illuminates between the B+ circuit terminal A and the ground circuit terminal B.

  • If the test lamp does not illuminate
  1. Ignition OFF, remove the test lamp. Disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
  2. Test for less than 2 Ω in the control circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, replace the X50A Fuse Block - Underhood.
  • Go to next step: If the test lamp illuminates

8. Connect a test lamp between the control circuit terminal C and the ground circuit terminal A.

9. Verify the test lamp does NOT turn ON and OFF when commanding the Rear Wiper On and Off with a scan tool.

  • If the test lamp turns ON and OFF

Test or replace the M45 Rear Wiper Motor.

  • Go to next step: If the test lamp does NOT turn ON and OFF

10. Ignition OFF, connect the harness connector at the M45 Rear Wiper Motor, ignition ON.

11. Verify the M45 Rear Wiper Motor is NOT activated.

  • If the M45 Rear Wiper Motor is activated
  1. Ignition OFF, disconnect the harness connector at the M45 Rear Wiper Motor, ignition ON.
  2. Test for less than 1 V between the control circuit terminal C and ground.
    • If 1 V or greater, repair the short to voltage on the circuit.
    • If less than 1 V, replace the M45 Rear Wiper Motor.
  • Go to next step: If the M45 Rear Wiper Motor is not activated

12. Connect a 20 A fused jumper wire between the circuit terminal 19 X2 and B+.

13. Verify the M45 Rear Wiper Motor activates.

  • If the M45 Rear Wiper Motor does not activate
  1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the M45 Rear Wiper Motor, ignition ON.
  2. Test for infinite resistance between the control circuit and ground.
    • If less than Infinite resistance, repair the short to ground on the circuit.
    • Go to next step: If infinite resistance
  3. Test for less than 2 Ω in the control circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, replace the M45 Rear Wiper Motor.
  • Go to next step: If the M45 Rear Wiper Motor activates

14. Ignition OFF, connect the X2 harness connector at the X50A Fuse Block - Underhood. Disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.

15. Verify the M45 Rear Wiper Motor is not activated.

  • If the M45 Rear Wiper Motor is activated
  1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block - Underhood, ignition ON.
  2. Test for less than 1 V between the control circuit terminal 16 and ground.
    • If 1 V or greater, repair the short to voltage on the circuit.
    • If less than 1 V, replace the X50A Fuse Block - Underhood.
  • Go to next step: If the M45 Rear Wiper Motor is not activated

16. Connect a 10 A fused jumper wire between the control circuit terminal 8 and B+.

17. Verify the M45 Rear Wiper Motor activates.

  • If the M45 Rear Wiper Motor does not activate
  1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
  2. Test for infinite resistance between the control circuit terminal 16 and ground.
    • If less than infinite resistance, repair the short to ground on the circuit.
    • Go to next step: If less than infinite resistance
  3. Test for less than 2 Ω in the control circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, test or replace the X50A Fuse Block - Underhood.
  • Go to next step: If the M45 Rear Wiper Motor activates

18. Test or replace the K9 Body Control Module.

Component Testing

Windshield Wiper/Washer Switch

1. Ignition OFF, disconnect the harness connector at the S82 Windshield Wiper/Washer Switch.

2. Test for infinite resistance between the signal terminal 5 and the low reference terminal 1 with the rear window washer switch in the open position.

  • If less than infinite resistance

Replace the S82 Windshield Wiper/Washer Switch.

  • Go to next step: If infinite resistance

3. Verify the resistance reading is within the range specified below between the signal circuit terminal 5 and the low reference circuit terminal 1 by cycling the switch between Rear Wiper position and Rear Washers position.

  • Rear Wiper : 624-644 Ω
  • Rear Wiper Sweep : 1.99-2.01 kΩ
  • Rear Washer : 6.11-6.13 kΩ
  • If not within range specified

Replace the S82 Windshield Wiper/Washer Switch.

  • Go to next step: If within range specified

4. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

  • Rear Window Wiper Motor Replacement (5-Door Hatchback 68)Rear Window Wiper Motor Replacement (5-Door Wagon 35)
  • Windshield Wiper and Washer Switch Replacement
  • Control Module References or BCM replacement, programming and setup

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