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

### Circuit Description

The ECU-B Fuse supplies battery voltage at all times to the AIR BAG warning lamp that is connected to the AIR BAG Indicator Control connector C2 terminal 2. When the ignition switch is turned to ACC or ON, battery voltage is applied to the inflatable restraint Sensing and Diagnostic Module (SDM) at connector C2 terminal 4. The SDM responds by illuminating the AIR BAG warning lamp for approximately six seconds while performing diagnostic tests on the SIR system. The IGN Fuse supplies battery voltage to the SDM at connector C2 terminal 3 when the ignition switch is in the ON or START positions.

### Test Description

1. This test checks for a short to ground in the air bag indicator control circuit or the instrument cluster.

2. This test checks for a short to ground in the air bag indicator control circuit to the instrument cluster.

3. This test checks for a short to ground in the air bag indicator control circuit to the data link connector (underhood).

4. This test checks for a short to ground in the air bag indicator control circuit between the SDM and SP255.

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 | Turn the ignition switch to the LOCK position. Is the AIR BAG warning lamp ON? | -- | Go to Step 3 | Go to Step 12
3 |

1. Turn the ignition switch to the LOCK position.
2. Remove the ECU-B Fuse.
3. Disconnect the splice pack SP255.
4. Measure the resistance by backprobing between the instrument cluster harness connector C1 terminal 10 and ground.

Is the resistance measured within the specified values?

0-5 ohms

Go to Step 4

Go to Step 7

4 |

1. Disconnect the instrument cluster connector C1.
2. Measure the resistance between the instrument cluster harness connector C1 terminal 10 and ground.

Is the resistance measured less than the specified value?

OL

(Infinite)

Go to Step 6

Go to Step 5

5 | Repair a short to ground condition in the BLK/YEL wire between SP255 and the instrument cluster. Refer to Wiring Repair in this section. Are all the repairs complete? | -- | Go to Step 20 | --
6 | Service the instrument cluster. Refer to Instrument Cluster System Check in Instrument Panel, Gauges and Console. Are all the repairs complete? | -- | Go to Step 20 | --
7 | Measure the resistance between the Data Link Connector (Underhood) terminal 5 (AB) and ground. Is the resistance measured within the specified values? | 0-5 ohms | Go to Step 8 | Go to Step 9
8 | Repair a short to ground condition in the BLK/YEL wire between SP255 and the DLC. Refer to Wiring Repair . Are all the repairs complete? | -- | Go to Step 20 | --
9 |

1. Disconnect the inflatable restraint Sensing and Diagnostic Module (SDM).
2. Measure the resistance between the SDM connector C2 terminal 2 and ground.

Is the resistance measured less than the specified values?

OL

(Infinite)

Go to Step 10

Go to Step 11

10 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Are all the repairs complete? | -- | Go to Step 20 | --
11 | Replace SP255. Refer to Wiring Repair . Are all the repairs complete? | -- | Go to Step 20 | --
12 | Remove the ECU-B Fuse. Is the ECU-B Fuse good? | -- | Go to Step 13 | Go to Step 16
13 | Measure the voltage from each terminal of the ECU-B fuseholder. Is either voltage reading greater than the specified value? | 1 V | Go to Step 14 | Go to Step 17
14 |

1. Replace the ECU-B Fuse.
2. Measure the voltage by backprobing from the instrument cluster connector C3 terminal 13 to ground.

Is the voltage reading within the specified value?

9-14 V

Go to the Step 15

Go to Step 18

15 |

1. Remove the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.
2. Remove the AIR BAG warning lamp bulb.

Is the AIR BAG warning lamp bulb good?

--

Go to Step 6

Go to Step 19

16 | Repair a short to ground in the RED/GRN wire. Refer to Wiring Repair . Are all the repairs complete? | -- | Go to Step 20 | --
17 | Repair an open in the power feed to the ECU-B Fuse. Refer to Wiring Repair . Are all the repairs complete? | -- | Go to Step 20 | --
18 | Repair an open in the RED/GRN wire. Refer to Wiring Repair in this section. Are all the repairs complete? | -- | Go to Step 20 | --
19 | Replace the AIR BAG warning lamp bulb. Refer to Instrument Cluster Bulb Replacement in Instrument Panel, Gauges and Console. Are all the repairs complete? | -- | Go to Step 20 | --
20 | Reconnect all the SIR components. Make sure all the components are properly mounted. Have all the SIR components been properly mounted? | -- | Go to SIR Diagnostic System Check | --