Buick Regal: DTC B370B

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 Descriptor

DTC B370B

Rear Wiper Function Control Circuit

For symptom byte information, refer to Symptom Byte List.

Diagnostic Fault Information

1. Rear Wiper Inoperative
2. Rear Wiper Always ON

Circuit/System Description

The body control module (BCM) controls the rear wiper motor based on an input from the rear wiper switch, which is part of the windshield wiper/washer switch. The BCM monitors the windshield wiper/washer switch through two separate signal circuits and a low reference circuit. The rear wiper switch uses a resistor ladder to determine low speed, intermittent, and rear washer operation. The BCM monitors applies and monitors voltage on the rear wiper switch signal circuit. 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 will respond by commanding the specific rear wiper function.

The rear wiper motor is controlled by the BCM through the rear wiper relay. A constant B+ and ground are supplied to the rear wiper motor. When rear wiper operation is requested, the BCM will apply voltage to the rear wiper relay control circuit. This will cause the contacts in the rear wiper relay to close and apply B+ to the rear wiper motor through the rear wiper control circuit, enabling rear wiper operation. When the rear wiper request is no longer present, the contacts in the rear wiper relay will open, removing B+ from the rear wiper motor control circuit. The rear wiper motor will continue to operate using the constant B+ circuit until it is in the park position.

Conditions for Running the DTC

• Ignition ON
• The system voltage is between 9 - 16 V.

Conditions for Setting the DTC

B370B 02

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

Action Taken When the DTC Sets

Rear wiper operation is disabled.

Conditions for Clearing the DTC

The DTC will clear when the conditions for setting the DTC are no longer 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 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 Door Ajar Indicator Malfunction

• Go to next step: If the parameter changes

3. Verify the Scan Tool Rear Wiper Switch Parameter changes between ON and OFF when cycling the rear wiper switch 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

4. Verify the M45 Rear Wiper Motor cycles when commanding the rear wiper ON with the rear wiper switch

• If the M45 Rear Wiper Motor does not cycle

Refer to Refer to Circuit/System Testing - Rear Wiper Motor Malfunction

• Go to next step: If the M45 Rear Wiper Motor cycles

5. Verify the M45 Rear Wiper Motor returns to the park position when the rear wipers are turned OFF

• If the M45 Rear Wiper Motor does not return to the park position

Refer to Circuit/System Testing - Rear Wiper Motor Malfunction

• Go to next step: If the M45 Rear Wiper Motor returns to the park position

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.

• 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 harness connector at the M45 Rear Wiper Motor. 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 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

3. Ignition ON.

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

• 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, test or replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

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

6. Verify the test lamp does NOT turn ON and OFF when commanding the rear wiper ON and OFF with the rear wiper switch.

• 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

7. Ignition OFF, connect the harness connector at the M45 Rear Wiper Motor. Disconnect the X1 and X5 harness connector at the X50A Fuse Block - Underhood, It may take up to 2 min for all vehicle systems to power down.

8. Test for less than 10 Ω between each ground circuit terminal listed below and ground:

• Terminal K8 X1
• Terminal H2 X5
• 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

9. Ignition ON.

10. 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

11. Connect a 20 A fused jumper wire between both of the circuits listed below and B+.

• B+ Circuit Terminal H4
• Control Circuit Terminal 47 at X210

12. 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

13. 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.

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

• If the M45 Rear Wiper Motor is activated

1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood, ignition ON.
2. Test for less than 1 V between the control circuit terminal 10 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

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

16. 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 X1 harness connector at the X50A Fuse Block - Underhood.
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 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

17. 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 wiper switch in the OFF position.

• If less than infinite resistance

Replace the S82 Windshield Wiper/Washer Switch.

• Go to next step: If infinite resistance

3. Verify the resistance is within the range specified below between the signal circuit terminal 4 and the low reference circuit terminal 2 by cycling the switch between Rear Wiper position and Rear Washers position.

• Rear Wiper : 624 - 644 Ω
• Rear Wiper Sweep : 1.8 - 2.2 kΩ
• Rear Washer : 5.9 - 6.4 kΩ
• If not within the specific range

Replace the S82 Windshield Wiper/Washer Switch.

• Go to next step: If within the specific range

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)
• Engine Wiring Harness Junction Block Replacement (LTG) Engine Wiring Harness Junction Block Replacement (LGX)
• Windshield Wiper and Washer Switch Replacement
• Control Module References for body control module replacement, programming, and setup.

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