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DTC B370B

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 02

Rear Wiper Function Control Circuit Short to Ground

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Rear Wiper Switch Signal 2 1 1 -
Rear Window Wiper Control 1 1 2 -
Rear Window Wiper Relay Control B370B 02 1 2 -
Rear Window Wiper Ground - 1 1 -
1. Washer Inoperative 2. Washer Always ON


Circuit/System Description

The body control module (BCM) controls the single speed rear wiper motor by its active high output to the external rear wiper motor relay. When the BCM activates its output and applies battery to the coil of the relay, the relay energizes, allowing battery voltage from the fuse to be applied through the switched contacts of the rear wiper motor relay to the control input of the rear wiper motor . The motor then operates continuously at low speed.

Conditions for Running the DTC


• Ignition ON.

• The system voltage is between 9-16 V.


Conditions for Setting the DTC

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

Action Taken When the DTC Sets

Rear wiper operation is suspended.

Conditions for Clearing the DTC

A current DTC clears when the diagnostic runs and passes.

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

Operate the rear wiper by using the S82 Windshield Wiper/Washer Switch in the continuous and the intermittent position. Verify the M45 Rear Wiper Motor activates.

Circuit/System Testing


1. Ignition OFF, disconnect the KR7 Rear Wiper Relay.

2. Test for less than 5 Ω between the ground circuit terminal 86 and ground.

3. If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, test or replace the X50A Fuse Block - Underhood.

4. Connect a test lamp between the control circuit terminal 85 and ground.

5. Ignition ON, command the rear washer relay ON and OFF using the wiper switch. The test lamp should turn ON and OFF when changing between the commanded states.

6. 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.

7. 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 K9 Body Control Module.

8. If all circuits test normal, test or replace the KR7 Rear Wiper Relay.


Component Testing


Relay Test

1. Ignition OFF, connect the KR7 Rear Window Wiper Relay.

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

3. If the resistance is not within the specified range, replace the relay.

4. Test for infinite resistance between the following terminals:

• 30 and 86

• 30 and 87

• 30 and 85

• 85 and 87

5. If not the specified value, replace the relay.

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

7. If greater than the specified range, replace the relay.

8. Install a 10 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 5 Ω between terminals 30 and 87.

9. If greater than the specified range, replace the KR7 Rear Window Wiper Relay.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)

• Rear Window Wiper Motor Replacement

• Control Module References for BCM replacement, programming and setup