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Tahoe / Yukon Service Manual

DTC B158B or B158C - Liftgate Motor Power Open_Close Malfunction

DTC B158B or B158C - Liftgate Motor Power Open/Close Malfunction Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC B158B Rear Closure Open/Close Motor Open Control Circuit DTC B158C Rear Closure Open/Close Motor Close Control Circuit Symptom Byte Information: Symptom Byte List Diagnostic Fault Information

Circuit number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
4689 Control B158B 11 B158B 13 B158B 12 —
4690 Control B158C 11 B158C 13 B158C 12 —

Circuit/System Description The M31L Liftgate Power Assist Actuator - Left is a bi-directional motor and open or close operation is the result of the direction of the motor rotation. The K194 Rear Gate Module controls the M31L Liftgate Power Assist Actuator - Left through the control circuits by supplying power and ground in the appropriate polarity. The motor control circuits are monitored by the K194 Rear Gate Module prior to activation for a high or low condition and during motor operation for any irregular current flow conditions. When the B70 Liftgate Close Switch is pressed, the K194 Rear Gate Module will detect the voltage drop in the signal circuit 4657 and will command the M31L Liftgate Power Assist Actuator - Left to perform the CLOSE function. When the S45A Liftgate Release Switch-Exterior is pressed, the K9 Body Control Module will detect the voltage drop in the signal circuit 5797 and will send a serial data message to the K194 Rear Gate Module a liftgate open has been requested and will command the M31L Liftgate Power Assist Actuator - Left to perform the OPEN function. Conditions for Running the DTC M31L Liftgate Power Assist Actuator - Left = The component is commanded On Conditions for Setting the DTC B158B 11 Circuit 4689 is shorted to ground B158B 12 Circuit 4689 is shorted to voltage B158B 13 Circuit 4689 has an open/high resistance B158C 11 Circuit 4690 is shorted to ground B158C 12 Circuit 4690 is shorted to voltage B158C 13 Circuit 4690 has an open/high resistance Actions Taken When the DTC Sets M31L Liftgate Power Assist Actuator - Left = Disabled Conditions for Clearing the DTC A current DTC will clear when the diagnostic runs and passes. A history DTC will clear after 40 consecutive malfunction-free ignition cycles. Reference Information Schematic Reference Liftgate Schematics Connector End View Reference Master Electrical Component List Description and Operation Liftgate 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, vehicle doors Unlocked, liftgate mode switch in 3/4 or Full setting
  2. Verify the liftgate will perform the power open function when pressing the S45A Liftgate Release Switch - Exterior ⇒ If the liftgate does not power open Refer to Circuit/System Testing ⇓ If the liftgate does power open
  3. A fault that is not currently present may have been caused by a intermittent condition. Circuit/System Testing
  4. Ignition/Vehicle » Off
  5. Disconnect the electrical connector: X3 @ K194 Rear Gate Module
  6. Ignition » On / Vehicle » In Service Mode 3.1. Test for less than 1 V between the test points: Terminal 1 X3 @ Control module harness & Ground Terminal 5 X3 @ Control module harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇓ If less than 1 V
  7. Test for infinite resistance between the test points: 4.1. Ignition/Vehicle » Off 4.2. Test for infinite resistance between the test points: Terminal 1 X3 @ Control module harness & Ground Terminal 5 X3 @ Control module harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If less than infinite resistance
  8. Connect the electrical connector: X3 @ K194 Rear Gate Module
  9. Ignition » On / Vehicle » In Service Mode
  10. Verify DTC B158B 11, B158B 12, B158C 11, B158C 12 is not set ⇒ If the DTC is set Replace the component: K194 Rear Gate Module ⇓ If the DTC is not set
  11. Test or replace the component: M31L Liftgate Power Assist Actuator - Left Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Liftgate Power Assist Actuator Replacement For control module replacement, programming, and setup refer to: Control Module References