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

### Circuit Description

When the ignition switch is turned to the ON position, the inflatable restraint sensing and diagnostic and seat belt pretensioner module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM monitors the six deployment loops to detect leakage currents to ground and to B+ in the frontal air bag deployment loops, the side air bag deployment loops and the seat belt pretensioner deployment loops. Then, the deployment loop resistances are measured to ensure they are within their respective normal resistance ranges. During one portion of the RESISTANCE MEASUREMENT test, the SDM does the following:

• | Measures the voltage difference between the PASSENGER FRONTAL HIGH and the PASSENGER FRONTAL LOW.

• | Uses the measured voltage to calculate the resistance of the passenger frontal air bag deployment loop.

Upon passing these tests, the energy reserve is charged and the firing transistors are tested. The SDM then goes into CONTINUOUS MONITORING mode. The SDM service wait time is 1 minute. Refer to ENABLE/DISABLE procedures.

### Conditions for Setting the DTC

The passenger frontal air bag deployment loop resistance is less than 1.6 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 contact.

The RESISTANCE MEASUREMENT test checks for this malfunction. This test only occurs once each ignition cycle when the IGNITION is within the normal operating voltage range.

### Action Taken When the DTC Sets

• | The SDM sets a DTC 34.

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

### Conditions for Clearing the DTC

The resistance of the passenger frontal air bag deployment loop is more than 1.6 ohms. You must issue a scan tool Clear Codes command to clear a Current or History DTC.

### Diagnostic Aids

The following can cause an intermittent condition:

• | A short between CKT BA10 and CKT BP10.

• | A malfunctioning shorting bar within the inflatable restraint IP module yeloow 2-way connector.

• | A malfunctioning shorting bar within the inflatable restraint sensing and diagnostic and seat belt pretensioner module (SDM) wiring harness connector.

The diagnostic table directs the technician to note the entry value of the PASSENGER AIR BAG RESISTANCE. Comparing the value of the PASSENGER AIR BAG RESISTANCE over multiple ignition cycles can be helpful in determining if an intermittent condition exists.

### Test Description

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

1. This step checks to see if the inflatable restraint IP module is defective.

2. This step checks terminal 3 and terminal 4 of the SDM wiring harness connector for damaged terminals or corrosion.

3. This step determines if there is a short between CKT BA10 and CKT BP10 or if there is a malfunctioning SDM.

#### DTC 34 Passenger Frontal Air Bag Deployment 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. Install the scan tool.
3. Turn the ignition switch to the ON position.
4. Use the scan tool to request the SIR data list display.
5. Read and record on the repair order the passenger frontal 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. Remove the ignition key from the ignition switch.
3. Wait 1 minute for the SDM energy reserve capacitors to discharge.
4. Disconnect the inflatable restraint IP module yellow 2-way connector. Refer to Inflatable Restraint Instrument Panel Module Replacement .
5. Use the J 38715-55 adapter to connect the J 38715-A SIR Driver/Passenger Load Tool PASSENGER INFLATOR connector to the inflatable restraint IP module wiring harness connector.
6. Turn the ignition switch to the ON position.
7. Use the scan tool to request the SIR data list display.
8. Read the passenger frontal air bag deployment loop resistance PASSENGER AIR BAG RES.

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

1.6 ohms

Go to Step 5

Go to Step 4

4 |

1. Turn the ignition switch to the OFF position.
2. Remove the ignition key from the ignition switch.
3. Wait 1 minute for the SDM energy reserve capacitors to discharge.
4. Replace the inflatable restraint IP module. Refer to Inflatable Restraint Instrument Panel Module Replacement .

Is the repair complete?

--

Go to Step 12

--

5 |

1. Turn the ignition switch to the OFF position.
2. Remove the ignition key from the ignition switch.
3. Wait 1 minute for the SDM energy reserve capacitors to discharge.
4. Remove the J 38715-A SIR Driver/Passenger Load Tool.
5. 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 .
6. Check terminal 3 and terminal 4 of the SDM wiring harness connector for damaged terminals or corrosion.

Are the SDM wiring harness connector terminals damaged or corroded?

--

Go to Step 6

Go to Step 8

6 | Use the J 42250 Catera Terminal Repair Kit to repair the SDM wiring harness connector. Is the repair complete? | -- | Go to Step 7 | --
7 | Check for proper connection at terminal 3 and terminal 4 of the SDM. Are the SDM terminals damaged or corroded? | -- | Go to Step 9 | Go to Step 12
8 | Check for proper connection at terminal 3 and terminal 4 of the SDM. Are the SDM terminals damaged or corroded? | -- | Go to Step 9 | Go to Step 10
9 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement . Is the repair complete? | -- | Go to Step 12 | --
10 |

1. Insert the J 42113 Shorting Bar Tool into the SDM wiring harness connector above terminal 3 and terminal 4.
2. Zero the J 39200 Digital Multimeter (DMM).
3. Use the J 39200 to measure the resistance between terminal 3 and terminal 4 of the SDM wiring harness wiring harness connector.

Is the measured resistance less than the specified value?

OL

Go to Step 11

Go to Sensing and Diagnostic Module Integrity Check

11 |

1. Locate a short between CKT BA10 and CKT BP10.
2. Repair the short between CKT BA10 and CKT BP10.

Is the repair complete?

--

Go to Step 12

--

12 | Reconnect all the SIR components, making sure all the components are properly mounted. Have all SIR components been reconnected and properly mounted? | -- | Go to Step 13 | --
13 | Use the scan tool to clear all current and history SIR DTCs. Have all current and history SIR DTCs been cleared? | -- | Go to SIR Diagnostic System Check | --