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DTC B0091

DTC B0091

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 B0091 01

Center Front Impact Sensor Short to Battery

DTC B0091 02

Center Front Impact Sensor Short to Ground

DTC B0091 04

Center Front Impact Sensor Open Circuit

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

Diagnostic Fault Information

Circuit Short to Ground High Resistance Open Short to Voltage Signal Performance
Center Front Impact Sensor High Signal

B009102

B009104

B009104

B0091 01

B0091 39, B0091 71

Center Front Impact Sensor Low Reference

B009102

B009104

B009104

B0091 01

B0091 39, B0091 71



Circuit/System Description

The impact sensors are equipped on vehicles to supplement the Supplemental Inflatable Restraint (SIR) System performance. The impact sensors are electronic and are not part of the deployment loops, but instead provide inputs to the sensing and diagnostic module (SDM). The impact sensors can assist in determining the severity of some frontal and side collisions. The SDM uses the input from the impact sensors to assist in determining the severity of a collision further supporting air bag deployment. If the SDM determines a deployment is warranted, the SDM will cause current to flow through the deployment loops deploying the appropriate air bags. The center front impact sensor and side impact sensors utilize a bidirectional 2-wire circuit. The sensors modulate current on the interface to send identification, 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 sensors. When the ignition is turned ON and input power from the SDM is first detected, the sensors respond by performing internal diagnostics and sending an identification to the SDM. The SDM considers the identification to be valid if the response time is less than 5 seconds. The sensors continually communicate status messages to the SDM, which determines if a fault is present in the sensor circuit. When a fault is detected, the SDM may reset the sensors 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 V.

Conditions for Setting the DTC

B0091 01

The SDM has detected the center front impact sensor has been shorted to voltage


B0091 02

• The SDM has detected the center front impact sensor has been shorted to ground.

• The center front impact sensor current is greater than 23 mA for greater than 5 milliseconds.



B0091 04

• The SDM has detected an open/high resistance in the center front impact sensor.

• The SDM has not received a message from the center front impact sensor for greater than 375 milliseconds.



B0091 39

• The SDM has received a Not OK (NOK) message from the center front impact sensor.

• The SDM has not received a message.



B0091 3A

• The SDM has received identification message from the center front impact sensor which does not match the identification stored in the SDM memory.

• The SDM has reset the center front impact sensor twice without detecting the correct identification message.


B0091 71

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

Action Taken When the DTC Sets


• The SDM requests the instrument cluster to illuminate the AIR BAG indicator.

• The SIR System is disabled and no deployments are allowed.


Conditions for Clearing the DTC


• The condition responsible 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

Connector End View Reference

Component Connector End Views

Description and Operation

SIR 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

Circuit/System Verification


1. For DTC B0091 39, B0091 3A, B0091 71, replace the the B59 center front impact sensor.

2. For DTC B0091 01, B0091 02, B0091 04, perform the Circuit/System Testing.


Circuit/System Testing


1. Ignition OFF, disconnect the X2 harness connector at the K36 SDM.

2. Test for infinite resistance between the signal circuit terminal 23 and ground.

3. If not the specified value, test the signal circuit for a short to ground.

4. Ignition ON, test for less than 1V between the signal circuit terminal 23 and ground.

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

6. Ignition OFF, test for infinite resistance between the low reference circuit terminal 24 and ground.

7. If not the specified value, test the low reference circuit for a short to ground.

8. Ignition ON, test for less than 1V between the low reference circuit terminal 24 and ground.

9. If greater than the specified range, test the low reference circuit for a short to voltage.

10. Test for 1.8-5.5 Ω between signal circuit terminal 23 and low reference circuit terminal 24

11. If less than the specified range, replace the B59 center front impact sensor

12. If greater than the specified range, test the signal circuit and low reference circuit for an open/high resistance. If the circuits test normal, replace the B59 center front impact sensor

13. If all circuits test normal, replace the K36 SDM.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Front End Inflatable Restraint Discriminating Sensor Replacement

• Control Module References for SDM replacement, setup, and programming