GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 Regal 🢒 Body Systems 🢒 Wipers and Washers 🢒 Windshield 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

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Windshield Wiper High Speed Relay B+

1, 2

1, 2

--

--

Windshield Wiper Switch Low Signal

1

1

1

--

Windshield Wiper Switch High Signal

4

2

2

--

Windshield Wiper Motor Park Switch Signal

3

3

--

--

Front Wiper Relay Control

B3715 02

B3715 04

B3715 01

--

Windshield Wiper High Speed Relay Control

B3875 02

B3875 04

B3875 01

--

Windshield Wiper High Speed Relay Control

2

2

4

--

Front Wiper Motor Low Speed Control

1

1

4

--

Windshield Wiper Switch Low Reference

--

1, 2

1, 2

--

Windshield Wiper Motor Ground

--

1, 2, 3

--

--

Front Wiper Relay Ground

--

1

--

--

1. Delay or Low Speed Wipers Inoperative

2. High Speed Wipers Inoperative

3. Wipers Do Not Park

4. Wipers Always ON

Circuit/System Description

The Body Control Module (BCM) controls the wiper motor based on input from the windshield wiper / washer switch. The BCM monitors the wiper / washer switch through two separate signal circuits and a ground circuit. The windshield wiper switch high signal circuit is used to determine high speed wiper operation, the windshield wiper switch low signal is used to determine low speed, intermittent, and mist operation through the use of a resistor ladder, and the windshield washer switch signal circuit is used to determine washer operation.

The BCM controls the windshield wiper motor through two output controls, controlling two relays which determine the desired wiper speed, high or low.

Reference Information

Schematic Reference

Wiper/Washer Schematics

Connector End View Reference

Component Connector End Views

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. S78 Turn Signal/Multifunction Switch in the LOW position, verify the windshield wipers are cycling at low speed.
  2. S78 Turn Signal/Multifunction Switch in the HIGH position, verify the windshield wipers are cycling at high speed.
  3. S78 Turn Signal/Multifunction Switch in the INT position, cycling the delay adjustment switch from long delay to short delay. Verify the wiper delay time decreases from long delay to short delay as each delay position is selected.

Circuit/System Testing

Multifunction Switch Circuit Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the S78 Turn Signal/Multifunction Switch.
  2. Ignition OFF, test for less than 5 Ω between the ground circuit terminal 2 and ground.
    3. ⇒If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).
  3. If all circuits test normal, test or replace the S78 Turn Signal/Multifunction Switch.

Windshield Wiper Motor Circuit Malfunction

  1. Ignition OFF, disconnect KR12B Windshield Wiper Relay.
  2. Test for less than 5 Ω between the ground circuit terminal 85 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Test for less than 5 Ω between the ground circuit terminal 87A and ground.
    4. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 87 and ground.
    5. ⇒If the test lamp does not illuminate, test or replace the underhood fuse block.
  5. Install a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
  6. Using the S78 Turn Signal/Multifunction Switch, command the low speed wipers ON and OFF. The test lamp should turn ON and OFF as commanded.
    7. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module (BCM).
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).
  7. Ignition OFF, disconnect the KR12C Windshield Wiper Speed Control Relay.
  8. Test for less than 5 Ω between the control circuit terminal 30 at the KR12B Windshield Wiper Relay socket and the control circuit terminal 30 at the KR12C Windshield Wiper Speed Control Relay socket.
    9. ⇒If greater than the specified range, replace the underhood fuse block.
  9. Connect the KR12B Windshield Wiper Relay.
  10. Test for less than 5 Ω between the control circuit terminal 30 from the KR12C Windshield Wiper Speed Control Relay socket and ground.
    11. ⇒If greater than the specified range, test or replace the KR12B Windshield Wiper Relay.
  11. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 85 from the KR12C Windshield Wiper Speed Control Relay socket and ground.
    12. ⇒If the test lamp does not illuminate, test or replace the underhood fuse block.
  12. Install a test lamp between the control circuit terminal 30 from the KR12C Windshield Wiper Speed Control Relay socket and ground.
  13. Using the S78 Turn Signal/Multifunction Switch, command the low speed wipers ON. The test lamp should illuminate.
    14. ⇒If the test lamp does not illuminate, replace the KR12B Windshield Wiper Relay.
  14. Install a test lamp between the B+ circuit terminal from the KR12C Windshield Wiper Speed Control Relay socket and the control circuit terminal 86 from the KR12C Windshield Wiper Speed Control Relay socket.
  15. Using the S78 Turn Signal/Multifunction Switch, command the high speed wipers ON and OFF. The test lamp should turn ON and OFF as commanded.
    16. ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module (BCM).
    ⇒If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).
  16. Ignition OFF, connect the KR12C Windshield Wiper Speed Control Relay. Disconnect the harness connector X1 at the M75 Windshield Wiper Motor.
  17. Test for less than 5 Ω between the ground circuit terminal 3 and ground.
    18. ⇒If greater than the specified value, test the ground circuit for an open/high resistance.
  18. Connect a test lamp between the control circuit terminal 2 and ground.
  19. Using the S78 Turn Signal/Multifunction Switch, command the low speed wipers ON and OFF. The test lamp should turn ON and OFF as commanded.
    20. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the KR12C Windshield Wiper Speed Control Relay.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the KR12C Windshield Wiper Speed Control Relay.
  20. Connect a test lamp between the control circuit terminal 4 and ground.
  21. Using the S78 Turn Signal/Multifunction Switch, command the high speed wipers ON and OFF. The test lamp should turn ON and OFF as commanded.
    22. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the KR12C Windshield Wiper Speed Control Relay.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the KR12C Windshield Wiper Speed Control Relay.
  22. Wipers OFF, verify a test lamp illuminates between the signal circuit terminal 1 and ground.
    23. ⇒If the test lamp does not illuminate, test the signal circuit for a short to ground or an open high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).
  23. If all circuits test normal, test or replace the M75 Windshield Wiper Motor.

Component Testing

Multifunction Switch

Static Test

  1. Disconnect the X1 harness connector at the S78 Turn Signal/Multifunction Switch.
  2. With the S78 Turn Signal/Multifunction Switch in the HIGH position, test for less than 5 Ω between the low reference terminal 2 and the signal terminal 1.
    3. ⇒If greater than the specified value, replace the S78 Turn Signal/Multifunction Switch.
  3. While cycling the S78 Turn Signal/Multifunction Switch through each delay and speed position, test for the specified resistance between the low reference terminal 2 and the signal terminal 3.

Note: If the switch tests open in any switch position other than OFF, test the signal circuits for a short to voltage before replacing the switch.

Wiper Switch Values

Switch Position

Resistance

Off

Infinite

Mist

300-364 Ω

Delay 1

3.48k-4.25k Ω

Delay 2

2.52k-3.08k Ω

Delay 3

1.78k-2.18k Ω

Delay 4

1.17k-1.44k Ω

Delay 5

697-951 Ω

Low

300-364 Ω

High

300-364 Ω

⇒If any switch position is not within the specified range, replace the S78 Turn Signal/Multifunction Switch.

Windshield Wiper Motor

Dynamic Test

  1. Ignition OFF, disconnect the harness connector X1 at the M75 Windshield Wiper Motor.
  2. Install a 25 A fused jumper wire between the control terminal 2 and 12 V. Install a jumper wire between the ground terminal 3 and ground.
  3. Verify the M75 Windshield Wiper Motor is operating in the low speed mode.
    4. ⇒If the M75 Windshield Wiper Motor is not in the low speed mode, replace the M75 Windshield Wiper Motor.
  4. Install a 25 A fused jumper wire between the control terminal 4 and 12 V. Install a jumper wire between the ground terminal 3 and ground.
  5. Verify the M75 Windshield Wiper Motor is operating in the high speed mode.
    6. ⇒If the M75 Windshield Wiper Motor is not in the high speed mode, replace the M75 Windshield Wiper Motor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure

    •  Windshield Wiper Motor Replacement
    •  Relay Replacement
    •  Windshield Wiper and Washer Switch Replacement
    •  Control Module References for BCM replacement, setup, and programming