For 1990-2009 cars

### 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 B0100 : Electronic Front End Sensor 1 Performance
DTC B0101 : Discard Electronic Front End Sensor 1
DTC B0102 : Incorrect Electronic Front End Sensor 1 Installed
DTC B0103 : Electronic Front End Sensor 2 Performance
DTC B0104 : Discard Electronic Front End Sensor 2
DTC B0105 : Incorrect Electronic Front End Sensor 2 Installed

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Front Impact Sensor Signal Circuit Left/Right | B0100, B0103 | B0100, B0103 | B0100, B0103 | B0100, B0103 | B0100, B0103
Front End Sensor Low Reference Circuit Left/Right | -- | B0100, B0103 | B0100, B0103 | -- | B0100, B0103

### Circuit/System Description

The inflatable restraint electronic frontal sensor (EFS) utilizes a unidirectional 2-wire circuit. The EFS modulates current on the interface to send ID, state of health (SOH), and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). The SDM serves as a power source and a ground for the EFS. When the ignition is turned ON and input power from the SDM is first detected, the EFS will respond 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 EFS continually communicates status messages to the SDM, which determines if a fault is present in the EFS circuit. When a fault is detected, the SDM resets the EFS twice by removing and reapplying power. If the fault is still present, the SDM will set a diagnostic trouble code (DTC).

### Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

### Conditions for Setting the DTC

#### B0100 and B0103

• | A valid ID message is not received within 5 seconds of the EFS being powered up.

• | Status message is not received.

• | The SDM has failed twice to reset the EFS.

#### B0102 and B0105

• | The SDM has received an ID message from the EFS that does not match the ID stored in the SDM memory.

• | When 2 EFS resets are attempted without the correct identification being detected by the SDM.

#### B0101 and B0104

Will set when the SDM has received a NOK (Not OK) message from the EFS.

### Action Taken When the DTC Sets

• | The SDM commands the AIR BAG indicator ON.

• | The SDM attempts to reset the EFS.

### Conditions for Clearing the DTC

• | The condition for setting the DTC no longer exists.

• | A history DTC will clear once 255 malfunction-free ignition cycles have occurred.

### Diagnostic Aids

The following can cause an intermittent condition:

• | A short between the EFS signal and voltage circuits

• | High or low resistance in the EFS signal and voltage circuits

• | Inspect the EFS signal and voltage circuits carefully for cutting and/or chafing.

• | Verify the correct EFS is installed in the vehicle.

### Reference Information

#### Schematic Reference

SIR Schematics

#### Connector End View Reference

SIR Connector End Views

#### Description and Operation

SIR System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

Important: Refer to SIR Service Precautions.

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

• | The front end sensor

• | The SDM module

• | The front end sensor wiring harness connector

• | The SDM wiring harness connector

1. Verify that DTC B0101, B0102, B0104, or B0105 are not set.

⇒ | If DTC B0101 or B0102 is set replace the left EFS. If the DTC resets, replace the SDM.

⇒ | If DTC B0104 or B0105 is set replace the right EFS. If the DTC resets, replace the SDM.

2. Ignition OFF, disconnect the harness connector at the appropriate front end sensor and the harness connector at the SDM.

• | If DTC B0100 is set disconnect the left EFS

• | If DTC B0103 is set disconnect the right EFS

3. Test for less than 1 volt between the signal circuit terminal B and ground.

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

4. Test for infinite resistance between the signal circuit terminal B and ground.

⇒ | If greater than the specified range, test the signal circuit short to ground.

5. Test for less than 1 ohm between the low reference circuit terminal A and the SDM connector terminal listed below:

• | If DTC B0100 is set, SDM terminal 26

• | If DTC B0103 is set, SDM terminal 27

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance.

6. Connect the SDM and EFS connectors.
7. Verify that DTC B0100 or B0103 are not set.

⇒ | If DTC B0100 is set replace the left EFS. If the DTC resets, replace the SDM.

⇒ | If DTC B0103 is set replace the right EFS. If the DTC resets, replace the SDM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Inflatable Restraint Front End Sensor Replacement

• | SIR/SRS Wiring Repairs

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