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.

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

Scan Tool Reference

Control Module References for diagnostic tester information.

Operate the rear wiper by using the S78 Turn Signal/Multifunction Switch. Verify the M45 Rear Window Wiper Motor activates.

Multifunction Switch Circuit Malfunction

1. Ignition OFF, disconnect the 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.

⇒	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. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module (BCM).
4. Ignition OFF, test for less than 5 Ω between the signal circuit terminal 4 at the S78 Turn Signal/Multifunction Switch harness connector and the X2 harness connector terminal 12 at the K9 Body Control Module (BCM).

⇒	If greater than the specified value, test the ground circuit for an open/high resistance and a short to voltage.

5. If all circuits test normal, replace the S78 Turn Signal/Multifunction Switch.

Rear Wiper Motor Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the M45 Rear Window Wiper Motor.
2. Test for less than 5 Ω between the ground circuit terminal B and ground.

⇒	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 A and ground.

⇒	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 C and ground.

⇒	If the test lamp does not illuminate, test or replace the X50D Fuse Block - Underhood.

5. Install a test lamp between the control circuit terminal A and the ground circuit terminal B.
6. Using the S78 Turn Signal/Multifunction Switch, command the rear wiper ON and OFF. The test lamp should turn ON and OFF as commanded.

⇒	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. If all circuits test normal, test or replace the M45 Rear Window Wiper Motor.

Relay Test

1. Ignition OFF, connect the harness connector X2 at the X50D Fuse Block - Underhood.
2. Disconnect the harness connector X4 at the K9 Body Control Module (BCM).
3. Test for 60-200 Ω between terminal 10 X4 and ground.

⇒	If the resistance is not within the specified range, test the control circuit for a short to ground or an open/high resistance.

⇒	If all circuits test normal, test or replace the X50D Fuse Block - Underhood.

Dynamic Test

1. Ignition OFF, disconnect the harness connector at the M45 Rear Window Wiper Motor.
2. Install a 25 A fused jumper wire between the control terminal A and 12 V. Install a jumper wire between the ground terminal B and ground.
3. Verify the M45 Rear Window Wiper Motor is operating.

⇒	If the M45 Rear Window Wiper Motor is not operating, replace the M45 Rear Window Wiper Motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.