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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 27 (Supplemental Restraints System) >> Diagnostic Information and Procedures >> DTC B0021 or B0029 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
  • Refer to SIR Service Precautions .
  • Refer to SIR Disabling and Enabling .
  • Inspect all terminals for damage or corrosion when disconnecting connectors. Damage or corrosion in the following requires repair or replacement of the affected component/connector.
    • Roof rail air bag
    • Roof rail air bag wiring harness connector
    • Restraints Control module
    • Restraints Control module wiring harness connector
  • The connector and connector position assurance (CPA) may seat independent of each other. Both the connector and CPA should seat with an audible and/or tactile click.
  1. Ignition OFF.
  2. Verify the SIR system is disabled.
  3. Scan tool disconnected. Disconnect the harness connector at the appropriate F105 Roof Rail Air Bag. It may take up to 2 min for all vehicle systems to power down.
  4. Test for greater than 13 Ω between the control circuit terminals 1 and 2.
    • If 13 Ω or less 
    1. Disconnect the X2 harness connector at the K36 Restraints Control module.
    2. Test for infinite resistance between the two control circuits.
      • If less than infinite resistance, repair the short between the two circuits.
      • If infinite resistance, replace the K36 Restraints Control module.
    • Go to next step: If greater than 13 Ω 
  5. Ignition ON.
  6. Verify the SIR system is disabled.
  7. Test for less than 11 V between the control circuit terminals listed below and ground:
    • Control circuit terminal 1
    • Control circuit terminal 2
    • If 11 V or greater 
    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 control 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 less than 11 V 
  8. Ignition OFF.
  9. Verify the SIR system is disabled.
  10. Test for greater than 13 Ω between the control circuit terminals listed below and ground:
    • Control circuit terminal 1
    • Control circuit terminal 2
    • If 13 Ω or less 
    1. Disconnect the X2 harness connector at the K36 Restraints Control module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K36 Restraints Control module.
    • Go to next step: If greater than 13 Ω 
  11. Ignition OFF.
  12. Verify the SIR system is disabled.
  13. Install a 3 A fused jumper wire between the control circuit terminals 1 and 2. Ignition ON.
  14. Verify the scan tool Deployment Loop Resistance parameter is less than 2 Ω.
    • If 2 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 each control 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 2 Ω 
  15. Ignition OFF, connect the harness connector at the F105 Head Curtain Control Module, press in the CPA (if equipped) until an audible and/or tactile click is heard.
  16. Ignition ON, clear DTCs. Operate the vehicle within the Conditions for Running the DTC.
  17. Verify DTC B0021 or B0029 is not set.
    • If DTC B0021 or B0029 is set 

      Test or replace the F105 Head Curtain Control Module.

    • Go to next step: If DTC B0021 or B0029 is not set 
  18. A fault is not currently present and may be an intermittent condition.
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