Buick Regal: DTC B370A

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 provide an overview of each diagnostic category.

DTC Descriptor

DTC B370A

Rain Sensor

For symptom byte information, refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

B+ and ground is supplied at all times to the rain sensor. The rain sensor communicates with the body control module (BCM) via serial data. When the ignition is in the ON or ACCESSORY position and the windshield wiper/washer switch is in the intermittent delay position, the BCM monitors the rain sensor data to determine the rain build up on the windshield. As rain builds up on the windshield, the BCM will command the wipers to activate.

The sensitivity of the wiper frequency is controlled by the intermittent delay of the windshield wiper/washer switch.

As the sensitivity is increased, the BCM will command more frequent wiper activation based on rain build up on the windshield.

Conditions for Running the DTC

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

Conditions for Setting the DTC

The system voltage is between 9 - 16 V.

Action Taken When the DTC Sets

• If the BCM loses communication with the Rain Sensor while the Rain Sensor is requesting single wipes, it shall fail soft the wipers operation to front wiper manual - intermittent with a fixed dwell time of 4 seconds.
• If the BCM loses communication with the Rain Sensor while the Rain Sensor is continuously requesting low, it shall fail soft the wipers operation to front wiper manual - low.
• If the BCM loses communication with the Rain Sensor while the Rain Sensor is continuously requesting high, it shall fail soft the wipers operation to front wiper manual - high.

Conditions for Clearing the DTC

A current DTC clears when the diagnostic runs and passes.

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 DTC U151A is not set.

• If the DTC is set

Refer to DTC U1500-U15FF

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

3. Place the S82 Windshield Wiper/Washer Switch in the intermittent delay setting and spray the outside of the windshield in the area of the B177 Rain Sensor with a water bottle. It may be necessary to increase the sensitivity of the intermittent delay to achieve windshield wiper operation.

4. Verify the windshield wipers operate at low speed.

• If the wipers are not operating at low speed

Refer to Circuit/System Testing.

• Go to next step: If the wipers are operating at low speed

5. All OK.

Circuit/System Testing

1. Ignition OFF, all vehicle systems OFF, disconnect the harness connector at the B117 Rain Sensor. 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 2 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.

4. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the test lamp.
2. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the B117 Rain Sensor.

• Go to next step: If the test lamp illuminates

5. Test for 5.0 - 10.0 V between the serial data circuit terminal 3 and ground.

• If less than 5.0 V

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the serial data 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 serial data 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 greater than 10.0 V

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the serial data circuit 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 between 5.0 - 10.0 V

6. Test or replace the B117 Rain Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Inside Air Moisture and Windshield Temperature Sensor Replacement
• Control Module References for BCM replacement, programming and setup

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