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 B0021 01 : RH Front Side Deployment Loop Short to Battery
DTC B0021 02 : RH Front Side Deployment Loop Short to Ground
DTC B0021 04 : RH Front Side Deployment Loop Open Circuit
DTC B0021 0D : RH Front Side Deployment Loop Resistance Above Threshold
DTC B0021 0E : RH Front Side Deployment Loop Resistance Below Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
RH Front Side Module High Circuit | B0021 02 | B0021 0D | B0021 04 | B0021 01 | B0021 0E
RH Front Side Module Low Circuit | B0021 02 | B0021 0D | B0021 04 | B0021 01 | B0021 0E

### Circuit/System Description

If a malfunction is detected, a DTC will be stored in non-volatile memory. During a side or frontal crash of sufficient force the inflatable restraint sensing and diagnostic module (SDM) will allow current to flow through the deployment loop in order to deploy the RH front side module. The SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. A shorting bar used within the RH front side module connector which will short together both RH front side module high and low circuits when the connector is disconnected. This will help to prevent unwanted deployment of the inflator module during servicing.

### Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

### Conditions for Setting the DTC

#### B0021 01

The RH front side module high and/or low circuit is short to voltage.

#### B0021 02

The RH front side module high and/or low circuit is short to ground.

#### B0021 04

The RH front side module high and/or low circuit is open.

#### B0021 0D

The RH front side module deployment loop resistance is more than 3.54 ohms.

#### B0021 0E

The RF side module deployment loop resistance is less than 1.77 ohms.

### Action Taken When the DTC Sets

• | The SDM commands the AIR BAG indicator ON via serial data communications.

• | 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 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

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

• | The I/P module

• | The SDM module

• | The I/P wiring harness connector

• | The SDM wiring harness connector

1. Ignition OFF, disconnect RH front side module in-line connector.
2. Disconnect the SDM connector. Refer to SDM replacement in Repair Instructions for connector location.
3. Test the high and low circuits between the SDM and RH front side module for a short to voltage, short to ground, short between circuits or open/high resistance. Verify that a short to voltage, short to ground, short between circuits or open/high resistance does not exist.

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

4. If all circuits test normal then replace the SDM.
5. Ignition ON, use a scan tool to observe the SIR DTC display. Verify DTC B0021 is set current.

⇒ | Replace the RH front side module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Inflatable Restraint Instrument Panel Module Replacement

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