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 and system voltage 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 driver frontal air bag deployment loop resistance is less than 1.7 ohms. The driver frontal air bag deployment loop consists of the following components.

• | Inflatable restraint steering wheel module.

• | Inflatable restraint steering wheel module coil.

• | Harness wiring of CKT BM30.

• | Harness wiring of CKT B30.

• | Connector terminal contacts, including shorting bars.

The deployment loop resistance test checks for this malfunction.

### 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 32 to set are no longer existing, History DTC 32 will set. History DTC 32 may be cleared using the scan tool.

### Diagnostic Aids

The following can cause an intermittent condition:

• | A short circuit between CKT BM30 and CKT B30.

• | A malfunctioning shorting bar in the inflatable restraint steering wheel module.

• | A malfunctioning shorting bar in the inflatable restraint steering wheel module coil .

• | A malfunctioning shorting bar on the inflatable restraint SDM harness connector above SDM harness connector terminals 1 and 2.

Inspect CKTs BM30 and B30 carefully for cutting and/or chafing. The diagnostic table directs the technician to note the value of DRIVER AIR BAG RES. Comparing the value of DRIVER AIR BAG RES. over multiple ignition cycles can be helpful in determining if an intermittent condition exists.

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 numbers below refer to step numbers on the diagnostic table.

1. This test determines whether the malfunction is in the inflatable restraint steering wheel module. This is done by substituting the known good resistance of the inflatable restraint steering wheel module. Then, observing if the malfunction is still present.

2. This test determines whether the malfunction is in the inflatable restraint steering wheel module coil.

3. This test determines whether the malfunction is between CKT BM30 and CKT B30.

#### DTC 32 Driver Air Bag Deploy. Loop Resistance Low

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. 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 on the repair order the driver frontal air bag deployment loop resistance DRIVER AIR BAG RES.

Has DRIVER AIR BAG RES. been read and recorded on the repair order?

--

Go to Step 3

--

3 |

1. Turn the ignition switch to the OFF position.
2. Wait one minute until the SDM energy reserve capacitors have discharge.
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 steering wheel module. Refer to Steering Wheel Inflator Module Replacement in Steering Wheel and Column--Tilt.
5. Use the J 38715-30 adapter to connect the J 38715-A SIR Driver/Passenger Load Tool STEERING COLUMN connector to the inflatable restraint steering wheel module integral harness connector.
6. Reconnect the negative battery cable.
7. Turn the ignition switch to the ON position.
8. Use the scan tool to request the SIR data list display.
9. Read the driver frontal air bag deployment loop resistance DRIVER AIR BAG RES.

Is the DRIVER AIR BAG RES. less than the specified value?

1.7 ohms

Go to Step 5

Go to Step 4

4 |

1. Turn the ignition switch to the OFF position.
2. Inspect the inflatable restraint steering wheel module integral harness connector for damage.
3. Ensure the nearby wiring is routed correctly.
4. Replace the inflatable restraint steering wheel module. Refer to Steering Wheel Inflator Module Replacement in Steering Wheel and Column--Tilt.

Is the replacement complete?

--

Go to Step 14

--

5 |

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. Remove the inflatable restraint steering wheel module coil from the top of the steering column. Refer to Steering Wheel Inflator Module Coil Replacement in Steering Wheel and Column--Tilt.
5. Use the J 38715-40 adapter to connect the J 38715-A SIR Driver/Passenger Load Tool BASE OF COLUMN connector to the inflatable restraint steering wheel module coil connector at the top of the steering column.
6. Turn the ignition switch to the ON position.
7. Use the scan tool to request the SIR data list display.
8. Read the driver frontal air bag deployment loop resistance DRIVER AIR BAG RES.

Is the DRIVER AIR BAG RES. less than the specified value?

1.7 ohms

Go to Step 7

Go to Step 6

6 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the J 38715-A SIR Driver/Passenger Load Tool.
3. Inspect the inflatable restraint steering wheel module coil for damage.
4. Inspect the inflatable restraint steering wheel module coil connecting wires for damage.
5. Replace the inflatable restraint steering wheel module coil. Refer to Steering Wheel Inflator Module Coil Replacement in Steering Wheel and Column--Tilt.

Is the replacement complete?

--

Go to Step 14

--

7 |

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 inflatable restraint Sensing and Diagnostic Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement .
5. Check for proper connection at terminals 1 and 2 on the SDM harness connector.

Are the terminals damaged and/or corroded?

--

Go to Step 7

Go to Step 8

8 | Use the J 42250 Catera Terminal Repair Kit to repair the SDM harness connector. Is the replacement complete? | -- | Go to Step 9 | --
9 | Check for proper connection at terminals 1 and 2 on the SDM. Are the terminals damaged and/or corroded? | -- | Go to Step 11 | Go to Step 14
10 | Check for proper connection at terminals 1 and 2 on the SDM. Are the terminals damaged and/or corroded? | -- | Go to Step 11 | Go to Step 12
11 | Replace the inflatable restraint Sensing and Diagnostic Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement . Is the replacement complete? | -- | Go to Step 14 - | --
12 |

1. Disconnect the J 38715-A SIR Driver/Passenger Load Tool.
2. Insert the J 42113 Shorting Bar Tool into the SDM harness connector terminal above terminals 1 and 2. This opens the short circuit bridge between terminals 1 and 2.
3. Zero the J 39200 Digital Multimeter.
4. Use the J 39200 Digital Multimeter to measure the resistance on the SDM harness connector from terminal 1 to terminal 2.

Is the resistance reading within the specified value?

0-0.5 ohms

Go to Step 13

Go to Integrity Check

13 | Repair the short circuit between CKT BM30 and CKT B30. Is the repair complete? | -- | Go to Step 14 | --
14 | Reconnect all the SIR system components. Ensure all the components are properly mounted. Are all the SIR system components reconnected and are all the SIR system components properly mounted? | -- | Go to Step 15 | --
15 | Clear the SIR diagnostic trouble codes. Are the SIR diagnostic trouble codes cleared? | -- | Go to SIR Diagnostic System Check | --