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 TURN-ON 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 in the frontal and side air bag inflator module and seat belt pretensioner circuits. Then, the SDM proceeds with the RESISTANCE MEASUREMENT test to measure the deployment loop resistances 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.

• | The measured leakage currents to ground in the passenger frontal air bag deployment loop are above a specified value caused by:

- | A short circuit from the passenger frontal air bag deployment loop to ground.

- | A short circuit between the passenger frontal air bag deployment loop and the communication signal return line of the LH or RH inflatable restraint Side Impact Sensor (SIS).

DTC 23 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 23 to set are no longer existing, History DTC 23 will set. History DTC 23 may be cleared using the scan tool.

### Diagnostic Aids

An inflatable restraint I/P module circuit short-to-ground or a short circuit between the communication signal return line of the LH or RH inflatable restraint Side Impact Sensor (SIS) can cause an intermittent condition. Inspect CKTs BA10 and BP10 carefully for cutting and/or chafing. A careful inspection of the circuits and components indicated on the DTC 23 Table is essential to make sure that the replacement SDM will not be damaged. Also inspect CKTs XB42 and XM430 carefully for cutting and/or chafing.

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 General Electrical Diagnosis Procedures in Wiring Systems. When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair .

### Test Description

The numbers below refer to step numbers on the diagnostic table.

1. This test determines whether the malfunction is in the inflatable restraint IP module. This is done by substituting the known good resistance of the load tool and then observing if the malfunction is still present.

2. This test determines whether the malfunction is in CKT BA10.

3. This test determines whether the malfunction is in CKT BP10.

#### DTC 23 Passenger Air Bag Deployment Loop Short to Ground

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 the OFF position.
2. Wait one minute until the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) energy reserve capacitors have discharged.
3. 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.

   .
4. Disconnect the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement .
5. Check for proper connection at terminals 3 and 4 on the SDM harness connector.

Are the terminals damaged and/or corroded?

--

Go to Step 3

Go to Step 5

3 | Replace the body harness. Are the repairs complete? | -- | Go to Step 4 | --
4 | Check for proper connection at terminals 3 and 4 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 6 | Go to Step 13
5 | Check for proper connection at terminals 3 and 4 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 6 | Go to Step 7
6 | Replace the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement . Are the repairs complete? | -- | Go to Step 13 | --
7 |

1. Disconnect the inflatable restraint IP module. Refer to On-Vehicle Service in this section.
2. Use the J 38715-45 adapter to connect the J 38715-A SIR Driver/Passenger Load Tool PASSENGER INFLATOR connector to the inflatable restraint IP module harness connector.
3. Reconnect the SDM harness connector to the SDM.
4. Reconnect the negative battery cable.
5. Turn the ignition switch to the RUN position.
6. Use the scan tool to request the SIR diagnostic trouble code display.

Is DTC 23 still current?

--

Go to Step 9

Go to Step 8

8 |

1. Turn the ignition switch to the OFF position.
2. Inspect the inflatable restraint IP module pigtail for damage.
3. Ensure the pigtail and the nearby wiring are routed correctly.
4. Replace the inflatable restraint IP module. Refer to Inflatable Restraint Instrument Panel Inflator Module On-Vehicle Service in this section.

Is the replacement complete?

--

Go to Step 13

--

9 |

1. Turn the ignition switch to the OFF position.
2. Wait one minute until the SDM energy reserve capacitors have discharged.
3. 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.

   .
4. Disconnect the SDM. Refer to On-Vehicle Service in this section.
5. Disconnect the J 38715-A SIR Driver/Passenger Load Tool.
6. Insert the J 42113 J 42113 Shorting Bar Tool into the SDM harness connector terminal above terminals 3 and 4. This opens the short circuit bridge between terminals 3 and 4.
7. Use the J 39200 to measure the resistance on the SDM harness connector from terminal 3 to terminal 7 (ground).

Is the resistance reading less then the specified value?

OL

Go to Step 10

Go to Step 11

10 | Repair the short to ground condition in CKT BA10. Is the repair complete? | -- | Go to Step 13 | --
11 | Measure the resistance on the SDM harness connector from terminal 4 to terminal 7 (ground). Is the resistance reading less than the specified value? | OL | Go to Step 12 | Go to AIR BAG Warning Lamp Does Not Come On
12 | Repair the short to ground condition in CKT BP10. Is the repair complete? | -- | Go to Step 13 | --
13 | Reconnect all the SIR system components. Ensure that all the SIR system components are properly mounted. Are all the SIR system components reconnected and are all the SIR system components properly mounted? | -- | Go to Step 14 | --
14 | Clear the SIR diagnostic trouble codes. Are the SIR diagnostic trouble codes cleared? | -- | Go to SIR Diagnostic System Check | --