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 passenger frontal air bag deployment loop resistance is less than 1.1 ohms. The passenger frontal air bag deployment loop consists of the following components.

• | Inflatable restraint IP module.

• | Harness wiring of CKT BA10.

• | Harness wiring of CKT BP10.

• | 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 34 to set are no longer existing, History DTC 34 will set. History DTC 34 may be cleared using the scan tool.

### Diagnostic Aids

The following can cause an intermittent condition:

• | A short circuit between CKT BM30 and B30.

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

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

• | A malfunctioning shorting bar on the SDM harness connector above SDM harness connector terminals 3 and 4.

Inspect CKTs BA10 and BP10 carefully for cutting and/or chafing. The diagnostic table directs the technician to note the value of PASSENGER AIR BAG RES. Comparing the value of PASSENGER 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 the deployment loop resistance measured by the inflatable restraint sensing and diagnostic module.

2. This test checks for proper connection of the orange 2-way connector.

3. This test isolates the malfunction to one side of to the inflatable restraint IP module yellow 2-way connector. This is done by substituting the known good resistance of the load tool and then observing if the malfunction is still present.

4. This test checks for proper contact or corrosion of the SDM connector.

5. This test checks for a short from CKT BA10 to CKT BP10.

#### DTC 34 Pass. 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 data link connector. Follow the directions in the scan tool instruction manual.
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 passenger air bag deployment loop resistance PASSENGER AIR BAG RES.

Has the PASSENGER 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 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 IP module. Refer to Inflatable Restraint Instrument Panel Module Replacement .
5. Check for proper connection at terminals 1 and 2 on the harness side of the inflatable restraint IP module orange 2-way connector.

Are the terminals damaged or corroded?

--

Go to Step 4

Go to Step 6

4 | Use the J 42250 Catera Terminal Repair Kit to repair the SDM wiring harness. Is the replacement complete? | -- | Go to Step 5 | --
5 | Check for proper connection at terminals 1 and 2 on the inflatable restraint IP module yellow 2-way connector. Are the terminals damaged and/or corroded? | -- | Go to Step 7 | Go to Step 17
6 | Check for proper connection at terminals 1 and 2 on the inflatable restraint IP module yellow 2-way connector. Are the terminals damaged and/or corroded? | -- | Go to Step 7 | Go to Step 8
7 | Replace the inflatable restraint IP module. Refer to Inflatable Restraint Instrument Panel Module Replacement . Has the inflatable restraint IP module been replaced? | -- | Go to Step 17 | --
8 |

1. 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.
2. Reconnect the negative battery cable.
3. Turn the ignition switch to the ON position.
4. Use the scan tool to request the SIR data list display.
5. Read the passenger air bag deployment loop resistance PASSENGER AIR BAG RES.

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

1.1 ohms

Go to Step 10

Go to Step 9

9 |

1. Turn the ignition switch to the OFF position.
2. Replace the inflatable restraint IP module. Refer to Inflatable Restraint Instrument Panel Module Replacement .

Has the inflatable restraint IP module been replaced?

--

Go to Step 17

--

10 |

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 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.
6. Inspect the shorting bar above terminals 3 and 4 on the SDM harness connector.

Are the terminals or the shorting bar damaged or corroded?

--

Go to Step 11

Go to Step 13

11 | Use the J 42250 Catera Terminal Repair Kit to repair the SDM wiring harness. Is the replacement complete? | -- | Go to Step 12 | --
12 |

1. Check for proper connection at terminals 3 and 4 on the SDM.
2. Inspect the shorting bar lifting tab above terminals 3 and 4 on the SDM.

Are the terminals or the shorting bar lifting tab damaged or corroded?

--

Go to Step 14

Go to Step 17

13 |

1. Check for proper connection at terminals 3 and 4 on the SDM.
2. Inspect the shorting bar lifting tab above terminals 3 and 4 on the SDM.

Are the terminals or the shorting bar lifting tab damaged or corroded?

--

Go to Step 14

Go to Step 15

14 | 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 . Is the replacement complete? | -- | Go to Step 17 | --
15 |

1. Insert the 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.
2. Zero the J 39200 Digital Multimeter.
3. Use the J 39200 Digital Multimeter to measure the resistance between the SDM terminals 3 and 4.

Is the resistance reading less than the specified value?

OL

Go to Step 16

Go to Integrity Check

16 | Repair a short from CKT BA10 to BP10. Is the repair complete? | -- | Go to Step 17 | --
17 | Reconnect all the SIR system components. Ensure 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 18 | --
18 | Clear the SIR diagnostic trouble codes. Are the SIR diagnostic trouble codes cleared? | -- | Go to SIR Diagnostic System Check | --