DTC B0021 or B0029

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptors DTC B0021 Left Front Roof Rail Air Bag High Control DTC B0029 Right Front Roof Rail Air Bag High Control Diagnostic Fault Information

Circuit	Short to Ground	Open/Hig Resistanc	h Low eResistanc	Short to e Voltage	Signal Performan
Control — Terminal 1, 2 @ F105LA Front and Rear and 3rd Row Roof Rail Airbag- Left	B0021 11	B0021 1B, B0021 13	B0021 1A	B0021 12	—
Control — Terminal 1, 2 @ F105RA Front and Rear and 3rd Row Roof Rail Airbag- Right	B0029 11	B0029 1B, B0029 13	B0029 1A	B0029 12	—

Circuit/System Description For an overview of the component/system, refer to: Supplemental Inflatable Restraint System Description and Operation

Circuit	Description
Control — Terminal 1	The output circuit is switched to 12 V to activate the component.
Control — Terminal 2	The output circuit is switched to ground to activate the component.

	Component	Description
	F105 Front and Rear and 3rd Row Roof Rail Airbag	The pyrotechnic unit contains an ignitor, which, when supplied with voltage, ignites the propellant in the gas generator.
	K36 Restraints Control Module	The control module monitors several sensors that can detect a collision. When a collision is detected, the control module will trigger certain air bags and

Component	Description
	seat belt pretensioners, depending on the angle and severity of the impact.

Conditions for Running the DTC Ignition voltage is between 9–16 V. Conditions for Setting the DTC B0021 12, B0029 12 The air bag control circuit is shorted to voltage for 2 seconds. B0021 11, B0029 11 The air bag control circuit is shorted to ground for 2 seconds. B0021 13, B0029 13 The air bag control circuit is open for 2 seconds. B0021 1B, B0029 1B The air bag deployment loop resistance is greater than 4.2 Ω for 2 seconds. B0021 1A, B0029 1A The air bag deployment loop resistance is less than 1.4 Ω for 2 seconds. Action Taken When the DTC Sets Air Bag Malfunction Indicator = On. Conditions for Clearing the DTC A current DTC will clear when the diagnostic runs and passes. A history DTC will clear after 100 consecutive malfunction-free ignition cycles. Diagnostic Aid

Note

The following diagnostic aids apply for both current and history DTCs. Refer to SIR Disabling and Enabling. Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with a reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections. An incorrectly seated connector can cause an open/high resistance condition. Check the circuit terminals for fretting or incorrectly seated connector if a DTC with symptom byte 1B is set. Reference Information Schematic Reference SIR Schematics Connector End View Reference Master Electrical Component List Description and Operation Supplemental Inflatable Restraint System Description and Operation Electrical Information Reference Circuit Testing Testing for Intermittent Conditions and Poor Connections Wiring Repairs Connector Repairs Scan Tool Reference Control Module References for scan tool information Special Tools EL-38125-580 Terminal Release Tool Kit Circuit/System Verification

Note

The condition may be intermittent and require driving the vehicle, then reviewing the snapshot to verify resistance parameters do not drop out or spike. Refer to Testing for Intermittent Conditions and Poor Connections

1. Verify the appropriate scan tool Deployment Loop Resistance parameters stay consistently between 2.1 and 4.0 Ω: F105LA Front and Rear and 3rd Row Roof Rail Airbag — Left F105RA Front and Rear and 3rd Row Roof Rail Airbag — Right ⇒ If less than 2.1 or greater than 4.0 Ω Refer to Circuit/System Testing. ⇓ If within 2.1 and 4.0 Ω
2. A fault is not currently present and may be an intermittent condition. Circuit/System Testing

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. Scan tool disconnected. It may take up to 2 min for all vehicle systems to power down.
2. Verify the SIR system is disabled.
3. Disconnect the harness connector at the appropriate F105 Roof Rail Air Bag.
4. Test for greater than 13 Ω between the control circuit terminals 1 and 2. ⇒ If 13 Ω or less 4.1. Disconnect the X2 harness connector at the K36 Restraints Control module. 4.2. 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. ⇓ 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 7.1. Ignition OFF. 7.2. Verify the SIR system is disabled. 7.3. Disconnect the X2 harness connector at the K36 Restraints Control module. Ignition ON. 7.4. 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. ⇓ 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 10.1. Disconnect the X2 harness connector at the K36 Restraints Control module. 10.2. 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. ⇓ If greater than 13 Ω
11. Install a 3 A fused jumper wire between the control circuit terminals 1 and 2. Ignition ON.
12. Verify the scan tool Deployment Loop Resistance parameter is less than 2 Ω. ⇒ If 2 Ω or greater 12.1. Ignition OFF. 12.2. Verify the SIR system is disabled. 12.3. Disconnect the X2 harness connector at the K36 Restraints Control module. 12.4. 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. ⇓ If less than 2 Ω
13. Ignition OFF, connect the harness connector at the F105 Roof Rail Airbag, press in the CPA (if equipped) until an audible and/or tactile click is heard.
14. Ignition ON, clear DTCs. Operate the vehicle within the Conditions for Running the DTC.
15. Verify DTC B0021 or B0029 is not set. ⇒ If DTC B0021 or B0029 is set Test or replace the F105 Roof Rail Airbag. ⇓ If DTC B0021 or B0029 is not set
16. A fault is not currently present and may be an intermittent condition. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Front and Rear and 3rd Row Roof Rail Airbag Replacement - Left Side Front and Rear and 3rd Row Roof Rail Airbag Replacement - Right Side SIR/SRS Wiring Repairs Control Module References for Restraints Control module replacement, programming and setup