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 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. The SDM service wait time is 1 minute. Refer to On-Vehicle Service for enable/disable procedures.

### Conditions for Setting the DTC

The driver side air bag deployment loop resistance is less than 1.1 ohms. The driver side air bag deployment loop consists of the following components:

• | Inflatable restraint driver seat module.

• | Harness wiring of CKT XB100.

• | Harness wiring of CKT AB11.

• | 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 DTC to set are no longer existing, the DTC may be cleared using the scan tool. If the resistance in the inflatable restraint driver seat module circuit is greater than 1.1 ohms, a Current DTC 78 will change to a History DTC 78, which may be cleared using the scan tool.

### Diagnostic Aids

The following can cause an intermittent condition:

• | A short circuit between CKT XB100 and AB11.

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

• | A malfunctioning shorting bar on the inflatable restraint SDM harness connector above SDM harness connector terminals 10 and 11.

• | A malfunctioning shorting bar in the inflatable restraint driver seat yellow 2-way electrical connector.

• | A malfunctioning shorting bar in the yellow 2-way in-line connector C208.

Inspect CKTs XB100 and AB11 carefully for cutting and/or chafing. The diagnostic table directs the technician to note the value of LH SIDE AIR BAG RESIST. Comparing the value of LH SIDE AIR BAG RESIST. 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 following numbers refer to the step numbers on the diagnostic table:

1. This test determines the deployment loop resistance measured by the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM).

2. This test isolates the malfunction to one side of the inflatable restraint driver seat module 2-way integral connector.

3. This test isolates the malfunction to one side of the inflatable restraint driver seat harness located under the LH front seat track cover.

4. This test checks for a short in CKT AB11 to XB100.

#### DTC 78 Driver Side Air Bag Deployment Loop Resistance Low

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the SIR Diagnostic 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 side air bag deployment loop resistance LH SIDE AIR BAG RESIST.

Has LH SIDE AIR BAG RESIST. been read and recorded on the repair order?

--

Go to Step 3

--

3 |

1. Turn the ignition switch OFF.
2. Wait 1 minute until the capacitors in the Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) have discharged.
3. Remove the driver seat back cover. Refer to Seat Back Replacement - Front in Seats.
4. Disconnect the inflatable restraint driver seat module 2-way integral connector.
5. Using the J 38715-30 adapter, connect the J 38715-A to the inflatable restraint driver seat module 2-way integral connector.
6. Turn the ignition switch to the ON position.
7. Using the scan tool, request the data list display.
8. Read the driver side air bag deployment loop resistance LH SIDE AIR BAG RESIST.

Is LH SIDE AIR BAG RESIST. less than the specified value?

1.1 ohms

Go to Step 5

Go to Step 4

4 | Replace the inflatable restraint driver seat module. Refer to Inflatable Restraint Seat Module Replacement - Driver . Is the replacement complete? | -- | Go to Step 14 | --
5 |

1. Turn the ignition switch to the OFF position.
2. Wait 1 minute until the capacitors in the Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) have discharged.
3. Disconnect the inflatable restraint driver seat module yellow 2-way harness connector C208 located under the LH seat track cover.
4. Using the J 38715-55 adapter, connect 38715-A to the inflatable restraint driver seat module 2-way connector C208.
5. Turn the ignition switch to the ON position.
6. Using the scan tool, request the data list display.
7. Read the driver side air bag deployment loop resistance LH SIDE AIR BAG RESIST.

Is the driver side air bag deployment loop resistance less than the specified value?

1.1 ohms

Go to Step 7

Go to Step 6

6 | Replace the inflatable restraint driver seat harness. Is the replacement complete? | -- | Go to Step 14 | --
7 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the J 38715-A.
3. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement .
4. Check for proper connection at terminal 10 and terminal 11 on the SDM harness connector.

Is the harness connector damaged or corroded?

--

Go to Step 8

Go to Step 10

8 | Replace the IP harness. Are the repairs complete? | -- | Go to Step 9 | --
9 | Check for proper connection at terminals 10 and 11 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 11 | Go to Step 14
10 | Check for proper connection at terminals 10 and 11 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 11 | Go to Step 12
11 | 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 14 | --
12 |

1. Insert J 42113 Shorting Bar Tool into the SDM harness connector terminal above terminals 10 and 11 on the SDM harness connect
2. Use the J 39200 to measure the resistance from the SDM harness connector terminal 10 to terminal 11.

Is the resistance reading within the specified values?

0-0.5 ohms

Go to Step 13

Go to Integrity Check

13 | Repair the short circuit between CKT AB11 and CKT XB100. Is the repair complete? | -- | Go to Step 14 | --
14 | Reconnect all of the SIR components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | Go to Step 15 | --
15 | Clear all the SIR DTCs. Have all the DTCs been cleared? | -- | Go to SIR Diagnostic System Check | --