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 00: Front End Sensor 3 (Center)DTC B0091 0F: Front End Sensor 3 (Center) Erratic
DTC B0091 39: Front End Sensor 3 (Center) Internal Electronic Failure
DTC B0091 3A: Front End Sensor 3 (Center) Incorrect Component Installed
DTC B0091 71: Front End Sensor 3 (Center) Invalid Serial Data Received
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Front End Impact Sensor High Signal | B0091 00 | B0091 0F | B0091 00 | B0091 00 | B0091 0F |
Front End Impact Sensor Low Reference | B0091 00 | B0091 0F | B0091 00 | B0091 00 | B0091 0F |
Circuit/System Description
The inflatable restraint front end sensor utilizes a unidirectional 2-wire circuit. The front end 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 end sensor. When the ignition is turned ON and input power from the SDM is first detected, the front end 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 end sensor continually communicates status messages to the SDM, which determines if a fault is present in the front end sensor circuit. When a fault is detected, the SDM may reset the front end 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 end sensor has been shorted to voltage, open, or shorted to ground. |
| • | The front end sensor current has been above 23 mA for longer than 5 milliseconds. |
| • | The SDM has not received a message from the front end sensor for more than 375 milliseconds. |
B0091 0F
The SDM has received erratic messages from the front end sensor.
B0091 39
| • | The SDM has received a NOK message from the front end sensor. |
| • | The SDM has not received a message. |
B0091 3A
| • | The SDM has received an ID message from the front end sensor, which does not match the ID stored in the SDM memory. |
| • | The SDM has reset the front end sensor twice without detecting the correct ID message. |
B0091 71
The SDM has received invalid serial data from the front end 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
Connector End View Reference
Description and Operation
SIR System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the front end sensor and the SDM.
- Ignition ON, test for less than 1 volt between the front end sensor signal circuit terminal 2 and ground.
- Ignition ON, test for less than 1 volt between the front end sensor low reference circuit terminal 1 and ground.
- Test for infinite resistance between the front end sensor signal circuit terminal 2 and ground.
- Test for infinite resistance between the front end sensor low reference circuit terminal 1 and ground.
- Test for less than 1 ohm between the SDM signal circuit terminal 38 and the front end sensor circuit terminal 2 harness connector.
- Test for less than 1 ohm between the SDM low reference circuit terminal 36 and the front end sensor circuit terminal 1 harness connector.
- If all circuits test normal, test or replace the front end sensor.
- Reconnect all SIR components. Ignition ON, verify the DTC is not set as current.
Important: When removing the connectors, inspect for damage or corrosion. Damage or corrosion to the following requires repair or replacement of the affected component/connector:
• Front end sensor • SDM module • Front end sensor wiring harness connector • SDM wiring harness connector
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. |
| ⇒ | If greater than the specified range, test the low reference circuit for a short to voltage. |
| ⇒ | If less than the specified value, test the signal circuit for a short to ground. |
| ⇒ | If less than the specified value, test the low reference circuit for a short to ground. |
| ⇒ | If greater than the specified range, test the signal circuit for an open/high resistance. |
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. |
| ⇒ | If the DTC resets as current, replace the SDM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for SDM replacement, setup, and programming |
