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Tahoe / Yukon Service Manual

DTC B1956-B1959

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 B1956 Front Side Door Window Regulator Motor - Driver DTC B1957 Front Side Door Window Regulator Motor - Passenger Symptom Byte Information: Symptom Byte List Circuit/System Description For an overview of the component/system, refer to: Power Windows Description and Operation

Circuit Description
B+ — M74D Front Side Door Window Regulator Motor - Driver Supplied from a fuse.
B+ — M74P Front Side Door Window Regulator Motor - Passenger Supplied from a fuse.
Ground — M74D Front Side Door Window Regulator Motor - Driver Chassis Ground
Ground — M74P Front Side Door Window Regulator Motor - Passenger Chassis Ground
Component Description
M74D Front Side Door Window Regulator Motor - Driver The motor M74D is a bidirectional DC motor that moves the component: Driver Power Window
M74P Front Side Door Window Regulator Motor - Passenger The motor M74P is a bidirectional DC motor that moves the component: Passenger Power Window

Conditions for Running the DTC Ignition » On / Vehicle » In Service Mode Conditions for Setting the DTC B1956 54, B1957 54 The BCM will automatically attempt to download the calibration program into the window motor (as will occur when the window motor has been replaced). If the first calibration program fails to load, the BCM will attempt to download the calibration program a second time. If this download fails, the BCM will set appropriate DTC. B1956 55, B1957 55 The BCM has detected that the window motor is not configured and the DTC can set for the following reasons: The battery has been disconnected The battery has been replaced The door wiring harness has been disconnected The window motor has been disconnected. Excessive and repeated Up and Down window switch use Actions Taken When the DTC Sets B1956 54 The driver window motor will be inoperative B1957 54 The passenger window motor will be inoperative B1956 55 Express Up function will be inoperative The driver information center will display the message: Open, then Close Driver Window B1957 55 Express Up function will be inoperative The driver information center will display the message: Open, then Close Passenger Window Conditions for Clearing the DTC B1956 54 The driver window motor must be replaced before DTC can be cleared B1956 55, B1957 55 DTC will automatically clear after performing express function normalization procedure: Window Motor Programming - Express Function B1957 54 The passenger window motor must be replaced before DTC can be cleared Reference Information Schematic Reference Moveable Window Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References Circuit/System Verification

  1. Ignition ON
  2. Verify the M74 Front Side Door Window Regulator Motor listed below performs the UP and DOWN functions while pressing and pulling the each window switch on the S79D Front Side Door Window Control Switch - Driver M74D Front Side Door Window Regulator Motor - Driver M74P Front Side Door Window Regulator Motor - Passenger ⇒ If the Up and Down functions do not work Replace the appropriate M74 Front Side Door Window Regulator Motor ⇓ If the UP and DOWN functions works
  3. Command the appropriate M74 Front Side Door Window Regulator Motor DOWN by pressing the window switch on the S79D Front Side Door Window Control Switch - Driver
  4. Verify the M74 Front Side Door Window Regulator Motor listed below performs the Express Up functions pulling and releasing the window switch on the S79D Front Side Door Window Control Switch - Driver M74D Front Side Door Window Regulator Motor - Driver M74P Front Side Door Window Regulator Motor - Passenger ⇒ If a M74 Front Side Door Window Regulator Motor does not perform the Express Up function Normalize the M74 Front Side Door Window Regulator Motor, refer to Window Motor Programming - Express Function. ⇓ If the M74 Front Side Door Window Regulator Motor performs the Express Up functions
  5. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
  6. Ignition ON
  7. Command the appropriate M74 Front Side Door Window Regulator Motor DOWN by pressing the window switch on the S79D Front Side Door Window Control Switch - Driver
  8. Verify the M74 Front Side Door Window Regulator Motor listed below performs the Express Up functions pulling and releasing the window switch on the S79D Front Side Door Window Control Switch - Driver M74D Front Side Door Window Regulator Motor - Driver M74P Front Side Door Window Regulator Motor - Passenger ⇒ If a M74 Front Side Door Window Regulator Motor does not perform the Express Up function Replace the M74 Front Side Door Window Regulator Motor ⇓ If the M74 Front Side Door Window Regulator Motor performs the Express Up function
  9. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Front Side Door Window Regulator Motor Replacement