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Tahoe / Yukon Service Manual

Rear Washer System Malfunction

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. Diagnostic Fault Information

Circuit Number Circuit Descriptio Short to n Ground Open/High Resistance Short to Voltage Signal Performan
391 Signal 1 1 1 —
2270 Control B12FC 11 1 2 —
392 Control 1 1 2 —
228 Ground — 1 — —
250 Ground — 1 — —
1. Rear Washer Inoperative 2. Rear Washer Always ON

Circuit/System Description The windshield washer system allows the driver to clean the vehicle’s windshield or rear window using a discrete switch. The washer system uses the S78 Turn Signal Switch as the primary means of driver control. The S78 Turn Signal Switch is a discrete input to the K9 Body Control Module. The K9 Body Control Module communicates with the K219 Lighting Control Module over CAN to control G24 Windshield Washer Pump activation. The K9 Body Control Module also communicates with the K219 Lighting Control Module to control B+ to the M45 Rear Wiper Motor during operation. The windshield washer uses a single windshield washer pump to provide fluid for both the front and rear washers. Changing the polarity of the motor will cause it to spin in opposite directions, feeding fluid to the front or rear. When rear washers are requested, the K219 Lighting Control Module applies voltage to the rear window washer pump relay control circuit. This causes the contacts in the KR6 Rear Window Washer Pump Relay to close and supplies voltage to the G24  Windshield Washer Pump. Ground for the G24 Windshield Washer Pump is provided through the KR11 Windshield Washer Pump Relay, which is switched to ground in it’s at-rest state. Reference Information Schematic Reference Wiper/Washer Schematics Connector End View Reference Master Electrical Component List 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 Windshield Wiper and Washer Switch Malfunction

  1. Ignition OFF and all vehicle systems OFF, disconnect the connector at the S78 Turn Signal Switch. It may take up to 2 min for all vehicle systems to power down.
  2. Verify a test lamp illuminates between the low reference circuit terminal 1 and B+. ⇒ If test lamp does not illuminate 2.1. Test circuit 6009 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 2.2. Replace the K9 Body Control Module. ⇓ If test lamp illuminates
  3. Ignition ON.
  4. Test for 4.8–5.2 V between circuit terminal 4 and ground. ⇒ If greater than 5.2 V 4.1. Test circuit 94 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 4.2. Replace the K9 Body Control Module. ⇒ If less than 4.8 V 4.1. Test circuit 94 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 4.2. Test circuit 94 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 4.3. Replace the K9 Body Control Module. ⇓ If 4.8–5.2 V
  5. Test or replace the S78 Turn Signal Switch. Rear Washer Pump Malfunction
  6. Ignition OFF, and all vehicle systems OFF, disconnect the connector at the G24 Windshield Washer Pump. It may take up to 2 min for all vehicle systems to power down.
  7. Connect a test lamp between the control circuit terminal 1 and the ground circuit terminal 2, ignition ON.
  8. Verify the test lamp does not turn ON and OFF when commanding the Windshield Washer Relay Active and Inactive with a scan tool. ⇒ If the test lamp turns ON and OFF Replace the G24 Windshield Washer Pump ⇓ If the test lamp does not turn ON and OFF
  9. Verify a test lamp illuminates between ground circuit terminal 2 and B+. ⇒ If the test lamp does not illuminate 4.1. Test circuit 228 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 4.2. Test circuit 250 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 4.3. Replace the X50A Engine Wiring Harness Junction Block. ⇓ If the test lamp illuminates
  10. Ignition OFF, connect the connector at the G24 Windshield Washer Pump. Disconnect the X1 connector at the X50A Engine Wiring Harness Junction Block, ignition ON
  11. Verify a test lamp does not illuminate between control circuit terminal A6 and ground. ⇒ If the test lamp illuminates 6.1. Test circuit 228 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 6.2. Replace the G24 Windshield Washer Pump. ⇓ If the test lamp does not illuminate
  12. Connect a 20 A fused jumper wire between the control circuit terminal A6 X1 and B+.
  13. Connect a 20 A fused jumper wire between the ground circuit terminal A5 X1 and ground.
  14. Verify the G24 Windshield Washer Pump activates. ⇒ If the G24 Windshield Washer Pump does not activate 9.1. Test circuit 392 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 9.2. Test circuit 392 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 9.3. Replace the G24 Windshield Washer Pump. ⇓ If the G24 Windshield Washer Pump activates
  15. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
  16. Connect the X1 connector at the X50A Engine Wiring Harness Junction Block. Disconnect the X2 connector at the K219 Lighting Control Module, ignition ON.
  17. Verify the G24 Windshield Washer Pump is not activated. ⇒ If the G24 Windshield Washer Pump is activated 12.1. Test circuit 2270 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 12.2. Replace the X50A Engine Wiring Harness Junction Block. ⇓ If the G24 Windshield Washer Pump is not activated
  18. Connect a 3 A fused jumper wire between the control circuit terminal 2 and B+.
  19. Verify the G24 Windshield Washer Pump activates. ⇒ If the G24 Windshield Washer Pump does not activate 14.1. Test circuit 2270 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 14.2. Test circuit 2270 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 14.3. Replace the X50A Engine Wiring Harness Junction Block. ⇓ If the G24 Windshield Washer Pump activates
  20. Replace the K219 Lighting Control Module. Component Testing Windshield Wiper/Washer Switch
  21. Ignition OFF, disconnect the harness connector at the S78 Turn Signal Switch.
  22. Test for infinite resistance between the signal terminal 4 and the low reference terminal 1 with the switch in the open position. ⇒ If less than infinite resistance Replace the S78 Turn Signal Switch. ⇓ If infinite resistance
  23. Test for 12.02k-13.3k Ω between the signal terminal 4 and the low reference terminal 1 with the switch in the wash position. ⇒ If 2 Ω or greater Replace the S78 Turn Signal Switch. ⇓ If less than 2 Ω
  24. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Windshield Washer Pump Replacement Turn Signal Switch Replacement Control Module References for body control module replacement, programming and setup.