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B0091




DTC B0091

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC B0091 00
- Center Front Impact Sensor

DTC B0091 01
- Center Front Impact Sensor Short to Battery

DTC B0091 02
- Center Front Impact Sensor Short to Ground

DTC B0091 05
- Center Front Impact Sensor Short to Battery or Open

DTC B0091 0F
- Center Front Impact Sensor Erratic

DTC B0091 39
- Center Front Impact Sensor Internal Electronic Failure

DTC B0091 3A
- Center Front Impact Sensor Incorrect Component Installed

DTC B0091 71
- Center Front Impact Sensor Invalid Serial Data Received

Circuit/System Description

The front impact sensor utilizes a unidirectional 2-wire circuit. The front impact sensor modulates current on the interface to send ID, state of health, and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). The SDM serves as a power source and a ground for the front impact sensor. When the ignition is turned ON and input power from the SDM is first detected, the front impact sensor responds by performing internal diagnostics and sending an ID to the SDM. The SDM considers the ID to be valid if the response time is less than 5 seconds. The front impact sensor continually communicates status messages to the SDM, which determines if a fault is present in the front impact sensor circuit. When a fault is detected, the SDM may reset the front impact sensor up to 2 times by removing and reapplying power to it. If the fault is still present, the SDM will set a DTC.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

B0091 00
* The front impact sensor has been shorted to voltage, open, or shorted to ground.
* The front impact sensor current has been above 23 mA for longer than 5 milliseconds.
* The SDM has not received a message from the front impact sensor for more than 375 milliseconds.

B0091 01
* The front impact sensor has been shorted to voltage.
* The front impact sensor current has been above 23 mA for longer than 5 milliseconds.
* The SDM has not received a message from the front impact sensor for more than 375 milliseconds.

B0091 02
* The front impact sensor has been shorted to ground.
* The front impact sensor current has been above 23 mA for longer than 5 milliseconds.
* The SDM has not received a message from the front impact sensor for more than 375 milliseconds.

B0091 05
* The front impact sensor has been shorted to voltage.
* The front impact sensor circuit is open.
* The front impact sensor current has been above 23 mA for longer than 5 milliseconds.
* The SDM has not received a message from the front impact sensor for more than 375 milliseconds.

B0091 0F

The SDM has received erratic messages from the front impact sensor.

B0091 39
* The SDM has received a NOK message from the front impact sensor.
* The SDM has not received a message.

B0091 3A
* The SDM has received an ID message from the front impact sensor, which does not match the ID stored in the SDM memory.
* The SDM has reset the front impact sensor twice without detecting the correct ID message.

B0091 71

The SDM has received invalid serial data from the front impact sensor.

Action Taken When the DTC Sets

* The SDM requests the instrument panel cluster (IPC) to illuminate the AIR BAG indicator.
* The frontal SIR System is disabled and no frontal deployments are allowed. Side deployments and rollover detection is still enabled.

Conditions for Clearing the DTC

* The condition for setting the DTC no longer exists.
* A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Reference Information
Schematic Reference

SIR Schematics [1][2]Air Bag Systems
Connector End View Reference

Component Connector End Views Connector Views
Description and Operation

SIR System Description and Operation Description and Operation
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. For DTC B0091 39, B0091 3A, B0091 71, replace the the B59 center front impact sensor.
2. For DTC B0091 00, B0091 01, B0091 02, B0091 05, and B0091 0F, perform the Circuit/System Testing.

Circuit/System Testing

Important: When removing connectors, inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector:


* Front impact sensor

* SDM module

* Front impact sensor wiring harness connector

* SDM wiring harness connector


1. Ignition OFF, disconnect the front impact sensor harness connector.
2. Remove the SDM harness connector.
3. Test for infinite resistance between the front impact sensor signal circuit terminal 1 and ground.

• If less than the specified value, test the circuit for a short to ground.

4. Ignition ON, test for less than 1 volt between the front impact sensor signal circuit terminal 1 and ground.

• If greater than the specified range, test the circuit for a short to voltage.

5. Ignition ON, test for less than 1 volt between the front impact sensor low reference circuit terminal 2 and ground.

• If greater than the specified range, test the circuit for a short to voltage.

6. Test for less then 1 ohm between the front impact sensor signal circuit terminal 1 and the SDM terminal.

• If greater than the specified range, test the circuit for an open/high resistance.

7. Test for less then 1 ohm between the front impact sensor low reference circuit terminal 2 and the SDM terminal.

• If greater than the specified range, test the circuit for an open/high resistance.

8. If the circuits test normal, replace the appropriate front impact sensor.
9. Reconnect all SIR components. Ignition ON, with a scan tool clear and recheck for DTCs.

• If the front impact sensor DTC returns and is current, replace the SDM.

Repair Instructions

* Inflatable Restraint Front End Sensor Replacement (1500) Inflatable Restraint Front End Sensor Replacement (1500)
* SIR/SRS Wiring Repairs SIR/SRS Wiring Repairs
* Control Module References Control Module References for SDM replacement, setup, and programming

Repair Verification

Ignition ON, use the scan tool to clear the DTCs, then recheck for DTCs.

If DTC B0091 was current, replace the SDM.

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