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Tahoe / Yukon Service Manual

DTC B1586 or B1587

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 B1586 Rear Closure Cinch Latch Motor Cinch Control Circuit DTC B1587 Rear Closure Cinch Latch Motor  Release 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
4681 Control B1586 11 B1586 13 B1586 12 —
4682 Control B1587 11 B1587 13 B1587 12 —

Circuit/System Description The liftgate latch has a bi-directional motor for the cinch or unlatch operations, the rear gate module controls the cinch and unlatch operation through the control circuits by supplying power and ground in the appropriate polarity to the control circuits which will cause the liftgate latch to perform the cinch or release function. Conditions for Running the DTC The system voltage is 9–16 V. Conditions for Setting the DTC B1586 11 4681= Short to Ground — For greater than 60 s B1586 12 4681= Short to Voltage — For greater than 60 s B1586 13 4681= Open/High Resistance — For greater than 60 s B1587 11 4682= Short to Ground — For greater than 60 s B1587 12 4682= Short to Voltage — For greater than 60 s B1587 13 4682= Open/High Resistance — For greater than 60 s Actions Taken When the DTC Sets The liftgate will not release and will be inoperative in the power and manual modes. 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. Diagnostic Aids If the liftgate will not release from the closed position, refer to Opening the Liftgate Without Electrical Power for the appropriate procedure Whenever the rear gate module loses power or is disconnected, the ignition must be cycled OFF then ON in order to reactivate the rear gate module. Reference Information Schematic Reference Liftgate Schematics Connector End View Reference Master Electrical Component List Description and Operation Liftgate Description and Operation Electrical Information Reference Testing for Intermittent Conditions and Poor Connections Circuit Testing Wiring Repairs Connector Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Ignition ON.
  2. Verify the A23C Liftgate Latch releases the liftgate when pressing the S45A Liftgate Release Switch - Exterior. ⇒ If the A23C Liftgate Latch does not release Refer to Circuit/System Testing ⇓ If the A23C Liftgate Latch does release
  3. Verify the A23C Liftgate Latch cinches the liftgate to the fully closed position while gently pushing the liftgate closed. ⇒ If the A23C Liftgate Latch does not cinch Refer to Circuit/System Testing ⇓ If the A23C Liftgate Latch cinch works
  4. A fault is not currently present and may be an intermittent condition Circuit/System Testing
  5. Ignition/Vehicle » Off
  6. Disconnect the electrical connector: M45 Rear Window Wiper Motor
  7. Ignition » On / Vehicle » In Service Mode
  8. Manually move the A23C Liftgate Latch to latched position.
  9. Verify the A23C Liftgate Latch performs the unlatch function when pressing the S45A Liftgate Release Switch - Exterior. ⇒ If the A23C Liftgate Latch does unlatch Replace the component: M45 Rear Window Wiper Motor ⇓ If the A23C Liftgate Latch does not unlatch
  10. Ignition/Vehicle » Off
  11. Connect the electrical connector: M45 Rear Window Wiper Motor
  12. Disconnect the electrical connector: A23C Liftgate Latch
  13. Connect a test lamp between the test points: Control circuit terminal 3 & Control circuit terminal 4
  14. Ignition » On / Vehicle » In Service Mode
  15. Operate the component: S45A Liftgate Control Switch - Exterior » Pressed Verify the test lamp state: Not Pressed = Test lamp Off S45A Liftgate Control Switch - Exterior » Pressed = Test lamp flashes On and Off ⇒ If the test lamp is always OFF 11.1. Ignition OFF, remove the test lamp, disconnect the X4 harness connector at the K194  Rear Gate Module 11.2. Test for infinite resistance between the control circuit listed below and ground: Control 4681 and ground Control 4682 and ground ⇒ If less than infinite resistance, repair the short to ground on the circuit. ⇓ If infinite resistance 11.3. Test for less than 2 Ω in the control circuit listed below end to end. Control 4681 end to end. Control 4682 end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, replace the K194 Rear Gate Module ⇒ If the test lamp is always ON 11.1. Ignition OFF, remove the test lamp, disconnect the X4 harness connector at the K194  Rear Gate Module ignition ON. 11.2. Test for less than 1 V between the control circuit listed below and ground: Control 4681 and ground Control 4682 and ground ⇒ If 1 V or greater, repair the short to voltage on the circuit. ⇒ If less than 1 V, replace the K194 Rear Gate Module ⇓ If the test lamp turns ON and OFF
  16. Test or replace the component: A23C Liftgate Latch Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Liftgate Latch Replacement Rear Window Wiper Motor Replacement For control module replacement, programming, and setup refer to: Control Module References