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Tahoe / Yukon Service Manual

DTC B12FC

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 Descriptors Rear Window Washer Relay Control Circuit For symptom byte information, refer to Symptom Byte List. Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
2270 Control B12FC 11 — — —
250 Ground — — — —

Circuit/System Description The KR6 Rear Window Washer Pump Relay supplies B+ to the G24 Windshield Washer Pump and is controlled by the K219 Lighting Control Module. The coil side of the relay receives a constant chassis ground and the switch side receives a constant B+. When rear washer operation is requested, the K219 Lighting Control Module will provide voltage to the coil side of the relay. This will energize the relay, closing the high current contact, and supply B+ to the G24 Windshield Washer Pump, enabling washer pump operation. Conditions for Running the DTC Ignition ON. The system voltage is between 9–16 V. Conditions for Setting the DTC B12FC 11 The K219 Lighting Control Module detects a short to ground in the rear window washer relay control circuit. Action Taken When the DTC Sets Rear washer operation is suspended. Conditions for Clearing the DTC A current DTC clears when the diagnostic runs and passes. A history DTC will clear after 40 consecutive malfunction-free ignition cycles. 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

  1. Ignition OFF and all vehicle systems OFF, disconnect the X1 connector at the X50A Fuse Block - Underhood. It may take up to 2 min for all vehicle systems to power down.
  2. Ignition ON. Connect a test lamp between control circuit terminal C2 and ground circuit terminal A4.
  3. Verify the test lamp turns on and off when commanding the Windshield Washer Pump On and Off with the S82 Windshield Wiper/Washer Switch. ⇒ If the test lamp is always on 3.1. 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. 3.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp is always off 3.1. 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. 3.2. 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. 3.3. Replace the K219 Lighting Control Module. ⇓ If the test lamp turns on and off
  4. Replace the X50A Fuse Block — Underhood. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Control Module References for K219 Lighting Control Module replacement, programming and setup.