For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using the 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 B1401: LF Side Impact Sensor (SIS) Short to Ground

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Side Impact Sensor Left Signal Circuit | B1401 | B1400 | B1400 | B1402 | B1400
Side Impact Sensor Left Voltage Circuit | B1401 | B1400 | B1400 | B1402 | B1400

### Circuit/System Description

The inflatable restraint side impact sensor (SIS) utilizes a unidirectional 2-wire circuit. The SIS 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 SIS. When the ignition is turned ON and input power from the SDM is first detected, the SIS 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 SIS continually communicates status messages to the SDM, which determines if a fault is present in the SIS circuit. When a fault is detected, the SDM resets the SIS twice 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

The wiring of the SIS is shorted to ground.

### Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON.

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

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

### Reference Information

#### Schematic Reference

SIR Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

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

• | The SIS

• | The SDM module

• | The SIS wiring harness connector

• | The SDM wiring harness connector

1. Disconnect the left SIS connector. Refer to SIS replacement in Repair Instructions for location of connector.
2. Remove the SDM connector. Refer to SDM replacement in repair instructions for connector location.
3. Test the signal and voltage circuits between the SDM and SIS. Verify that a short to ground, or low resistance does not exist.

⇒ | If any of the above conditions are found, make the appropriate repair.

4. Reconnect all SIR components. Ignition ON, use the scan tool to clear the DTCs then recheck for DTCs. Verify no DTCs are set.

⇒ | If DTC B1401 is current, replace the LF SIS. After replacement, refer to Repair Verification.

### Repair Instructions

• | Inflatable Restraint Side Impact Sensor Replacement

• | 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. Verify no DTCs are set.

⇒ | If DTC B1401 was current, replace the SDM.