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Home >> GMC >> 2021 >> Yukon AT4 >> Repair and Diagnosis >> Restraints >> Restraints Control Systems >> Seat Belts >> Diagnostic Information and Procedures >> DTC B1921 >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF. Disconnect the harness connector at the B60RR Passenger Seat Belt Reminder Occupant Presence Sensor - Right Rear, wait 120 seconds.
  2. Test for less than 30 Ω between the low reference circuit terminal 1 and ground.
    • If 30 Ω or greater 
    1. Ignition OFF.
    2. Verify the SIR system is disabled.
    3. Disconnect the X2 harness connector at the K36 Restraints Control Module.
    4. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K36 Restraints Control Module.
    • Go to next step: If less than 30 Ω 
  3. Ignition ON.
  4. Test for 4.75 - 5.25 V between the signal circuit terminal 2 and ground.
    • If less than 4.75 V 
    1. Verify the SIR system is disabled.
    2. Disconnect the X2 harness connector at the K36 Restraints Control Module.
    3. Test for infinite resistance between the signal circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
    4. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K36 Restraints Control Module.
    • If greater than 5.25 V 
    1. Ignition OFF.
    2. Verify the SIR system is disabled.
    3. Disconnect the X2 harness connector at the K36 Restraints Control Module. Ignition ON.
    4. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K36 Restraints Control Module.
    • Go to next step: If between 4.75 - 5.25 V 
  5. Replace the B60RR Passenger Seat Belt Reminder Occupant Presence Sensor - Right Rear.
    • Go to next step: If DTC B1921 is not set 
  6. All OK.