Buick Regal: DTC B3715 or B3875

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.

DTC Descriptors

DTC B3715

Windshield Wiper Relay Circuit

DTC B3875

Windshield Wiper High Speed Relay Circuit

For symptom byte information, refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The windshield wiper motor is controlled by the body control module (BCM) through the windshield wiper relay and the windshield wiper speed control relay. When low speed windshield wiper operation is requested, the BCM will apply voltage to the windshield wiper relay control circuit. This will cause the contacts in the windshield wiper relay to close and apply B+ to the windshield wiper motor through the windshield wiper low speed control circuit, enabling low speed wiper operation. When high speed windshield wiper operation is requested, the BCM continues to apply voltage to the windshield wiper relay control circuit and also applies ground to the windshield wiper speed control relay control circuit. This will cause the contacts in the windshield wiper speed control relay to close and apply B+ to the windshield wiper motor through the windshield wiper high speed control circuit, enabling high speed wiper operation. When the windshield wiper request is no longer present. the BCM uses an algorithm to keep relays engaged to keep wiper motor going at the last required speed until it sees that the motor is in the park position and then it will remove the necessary control drivers to stop the motor.

Conditions for Running the DTC

• The DTC runs only when a wiper output is actively being requested by the BCM.
• The system voltage is between 9 - 16 V.

Conditions for Setting the DTC

B3715 01

A short to voltage is detected in the windshield wiper relay control circuit.

B3715 02

A short to ground is detected in the windshield wiper relay control circuit.

B3715 04

An open or high resistance is detected in the windshield wiper relay control circuit.

B3875 01

A short to voltage is detected in the windshield wiper high speed relay control circuit.

B3875 02

A short to ground is detected in the windshield wiper high speed relay control circuit.

B3875 04

An open or high resistance is detected in the windshield wiper high speed relay control circuit.

Action Taken When the DTC Sets

The BCM will not activate the wiper output.

Conditions for Clearing the DTC

• A current DTC will clear when the condition for setting the fault is no longer present.
• A history DTC will clear after 50 consecutive ignition cycles without a fault present.

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 Testing

DTC B3715

1. Ignition OFF and all vehicle systems OFF, disconnect the KR12B Windshield Wiper Relay. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 85 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. 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. Ignition ON. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.

4. Verify the test lamp turns ON and OFF when commanding the Windshield Wiper Motor Relay On and Off with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, remove the test lamp, and disconnect the X4 harness connector at the K9 Body Control Module.
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 K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, remove the test lamp, and disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit 16 X4 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

5. Test or replace the KR12B Windshield Wiper Relay.

DTC B3875

1. Ignition OFF and all vehicle systems OFF, disconnect the KR12C Windshield Wiper Speed Control Relay.

2. Verify a test lamp Illuminates between the B+ circuit terminal 86 and ground.

• If the test lamp does not illuminate

Replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

3. Ignition ON. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.

4. Verify the test lamp turns ON and OFF when commanding the Windshield Wiper Motor Relay High and Stop with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, remove the test lamp, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal 24 X5 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Ignition OFF.
4. 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 K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, remove the test lamp, disconnect the X5 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit terminal 24 X5 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

5. Test or replace the KR12C Windshield Wiper Speed Control Relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the appropriate relay.

2. Test for 60 - 200 Ω between terminals 85 and 86.

• If less than 60 or greater than 200

Replace the relay.

• Go to next step: If between 60 - 200 Ω

3. Test for infinite resistance between the terminals listed below:

• 30 and 86
• 30 and 87
• 30 and 85
• 85 and 87
• If less than infinite resistance

Replace the relay.

• Go to next step: If infinite resistance

4. Test for less than 5 Ω between terminals 30 and 87A.

• If 5 Ω or greater

Replace the relay.

• Go to next step: If less than 5 Ω

5. Install a 10 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground.

6. Test for less than 5 Ω between terminals 30 and 87.

• If 5 Ω or greater

Replace the relay.

• Go to next step: If less than 5 Ω

7. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
• Control Module References for BCM replacement, setup, and programming

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