For 1990-2009 cars
SIR Components
SIR Schematics
Handling ESD Sensitive Parts Notice
SIR Caution
SIR Caution
Handling ESD Sensitive Parts Notice

### Circuit Description

The inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) performs tests to diagnose critical malfunctions within itself when the ignition switch is turned ON. The SDM monitors the six firing loops to detect leakage currents to ground and system voltage in the frontal and side air bag inflator module and seat belt pretensioner circuits. The deployment loop resistances are measured to ensure they are within their respective normal resistance ranges. Upon passing these tests, and if the energy reserve is charged up, the firing transistors are tested. The SDM then goes into Continuous Monitoring mode. The SDM service wait time is 1 minute. Refer to On-Vehicle Service for enable/disable procedures.

### Conditions for Setting the DTC

• | The ignition is within normal operating voltage range.

• | An internal fault in the driver Side Impact Sensor (SIS).

The driver Side Impact Sensor (SIS) loop consists of the following components:

• | The inflatable restraint Side Impact Sensor (LH) .

• | The harness wiring of CKT B41.

• | The harness wiring of CKT B42.

• | The harness wiring of CKT XB42.

• | The connector terminal contact.

DTC 71 will set once one of these conditions is met. This test is run during the SDM Turn-ON tests.

### Action Taken When the DTC Sets

• | The SDM sets a Diagnostic Trouble Code.

• | The SDM turns ON the AIR BAG warning lamp.

### Conditions for Clearing the DTC

Current and History DTC codes must be cleared using a scan tool Clear DTC Information command. If the circuit fault has been successfully repaired and the conditions which caused the Current DTC 71 to set are no longer existing, History DTC 71 will set. History DTC 71 may be cleared using the scan tool.

### Diagnostic Aids

An inflatable restraint driver Side Impact Sensor (SIS) circuit short-to-ground can cause an intermittent condition. Inspect CKTs B41, B42 and XB42 carefully for cutting and/or chafing. A careful inspection of the circuits and components indicated on the DTC 71 Table is essential to make sure that the replacement SDM will not be damaged.

When measurements are requested in this table, use J 39200 Digital Multimeter with the correct terminal adapter from J 35616 Connector Test Adapter Kit. When a check for proper connection is requested, refer to Intermittents and Poor Connections . When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair .

### Test Description

The following numbers refer to the step numbers in the diagnostic table:

1. This test checks the communication status of the driver side impact sensor.

#### DTC 71 Driver Side Impact Sensor Comms. Invalid

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the SIR Diagnostic System Check performed? | -- | Go to Step 2 | Go to SIR Diagnostic System Check
2 |

1. Turn the ignition switch to OFF position.
2. Connect a scan tool to the DLC.
3. Turn the ignition switch to the ON position.
4. Request the SIR data list display.
5. Read and record the repair order the communication status of the driver side impact sensor LH SIS MESSAGE STATUS.

Does LH SIS MESSAGE STATUS display the specified value?

NOK

Go to Step 3

Go to Integrity Check

3 |

1. Turn the ignition switch OFF.
2. Disconnect the negative battery cable. Refer to

   Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

   .
3. Replace the inflatable restraint side impact sensor (LH). Refer to Inflatable Restraint Side Impact Sensor Replacement .

Is the replacement complete?

--

Go to Step 4

--

4 | Reconnect all the SIR components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | Go to Step 5 | --
5 | Clear all the SIR DTCs. Have all the SIR DTCs been cleared? | -- | Go to SIR Diagnostic System Check | --