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Tahoe / Yukon Service Manual

DTC B10C8

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 Wiper Switch Signal 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
391 Signal — — — B10C8 23
6009 Ground — — — —

Circuit/System Description With the S78 Turn Signal Switch in the rear wipe position, the discrete signal circuit to the K9 Body Control Module is pulled down through a number of resistors within a resistor ladder to a low reference provided by the K9 Body Control Module. The number of resistors the signal travels through is dependent on the position selection made on the S78 Turn Signal Switch. The K9 Body Control Module interprets this range of voltage pull-down as a request for intermittent, low wiper, or rear washer activation, with each pull-down voltage value equating to the requested speed. Conditions for Running the DTC Ignition ON. The system voltage is between 9–16 V. Conditions for Setting the DTC B10C8 23 The K9 Body Control Module detects a request signal stuck on the rear window washer signal circuit. Action Taken When the DTC Sets Rear wiper/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, disconnect the connector at the S78 Turn Signal Switch.
  2. Verify a test lamp illuminates between low reference circuit terminal 8 and B+. ⇒ If the 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 the test lamp illuminates
  3. Ignition ON.
  4. Test for 4.8–5.2 V between signal circuit terminal 4 and ground. ⇒ If less than 4.8 V 4.1. Test circuit 391 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 391 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 greater than 5.2 V 4.1. Test circuit 391 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 4.8–5.2 V
  5. Replace the S78 Turn Signal Switch. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Turn Signal Switch Replacement Control Module References for BCM replacement, programming, and setup