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Tahoe / Yukon Service Manual

DTC C1178

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 DTC C1178 12 Column Lock Supply Voltage Circuit Short to Battery DTC C1178 14 Column Lock Supply Voltage Circuit Short to Ground/Open Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performance
807 B+ C1178 14 C1178 14 C1178 12 —

Circuit/System Description The vehicle theft deterrent subsystem provides the capability to lock or unlock the steering column electrically. The column lock module is allowed to unlock when power mode transitions to a non off power mode and an authenticated driver identification device is present. Once the column is unlocked, a crank request can be allowed. Conditions for Running the DTC The system voltage is between 9–16 V. The DTC can only run when the column lock module is awake. Conditions for Setting the DTC C1178 12 The column lock module detects a short to voltage on the ignition circuit when the power mode is in the RUN or CRANK for greater than 5 s. C1178 14 The column lock control detects a short to ground or an open in the ignition circuit when the power mode is in the OFF/ACC for greater than 3 s. Action Taken When the DTC Sets The column lock module will command the driver information center to display the service column lock warning message. The column lock module indicator is ON. Conditions for Clearing the DTC The DTC will be current for as long as the fault is present. The DTC will be a history DTC when the voltage is present and the power mode is OFF or ACC or when voltage is not present and the power mode is RUN or CRANK. A history DTC will clear after 50 ignition cycles. Reference Information Schematic Reference Column Lock Schematics Power Moding Schematics Connector End View Reference Master Electrical Component List Description and Operation Steering Wheel and Column 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

  1. Ignition ON.
  2. Verify there are no other DTCs set except C1178 ⇒ If any other DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no other DTCs are set except C1178
  3. Refer to Circuit/System Testing. Circuit/System Testing C1178 12
  4. Ignition OFF, disconnect the harness connector at the K60 Column Lock Module, ignition ON.
  5. Test for less than 1 V between the ignition circuit terminal 8 and ground. ⇒ If 1 V or greater Repair the short to voltage on circuit. ⇓ If less than 1 V
  6. Replace the K60 Column Lock Module. C1178 14
  7. Ignition OFF, disconnect the harness connector at the K60 Column Lock Module.
  8. Verify that a test lamp illuminates between the ignition circuit terminal 8 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is OK 2.1. Test ignition circuit 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. Verify the fuse is OK and there is voltage at the fuse. Refer to Power Mode Mismatch. ⇒ If the test lamp does not illuminate and the circuit fuse is open 2.1. Test ignition circuit 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 2.2. Replace the K60 Column Lock Module. ⇓ If the test lamp illuminates
  9. Replace the K60 Column Lock Module. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Control Module References for K60 Column Lock Module replacement, programming and setup.