For 1990-2009 cars

The following diagnostic procedure must be used when all circuitry outside the sensing and diagnostic module (SDM) has been found to operate properly, as indicated by following the appropriate DTC table. The procedure verifies the need for SDM replacement.

### Circuit Description

When the SDM recognizes ignition voltage greater than 9 volts at the SDM, the air bag indicator flashes 7 times to verify operation. At this time the SDM performs turn-on tests followed by resistance measurement tests and continuous monitoring tests.

When malfunction is detected, the SDM sets a current DTC and illuminates the air bag indicator.

When the malfunction is no longer detected and/or the ignition switch is cycled, the SDM will clear current DTCs and move them to a history file, except for the DTCs B1620, B1650, B1651, B1652, B1657. DTCs B1620, B1650, B1651, B1652, B1657 will not be cleared by a scan tool because these codes require replacement of the SDM. The SDM must be replaced only after the malfunction that set the DTC has been repaired.

Step | Action | Yes | No
--- | --- | --- | ---
Caution: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Caution in the Preface section. Caution: Refer to Sensing and Diagnostic Module Handling Caution in the Preface section. Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views
1 |

1. Turn the ignition to LOCK and remove the key.
2. Connect all SIR components and ensure that all the components are properly mounted.
3. Ensure that the ignition switch has been OFF for at least 30 seconds.
4. Observe the air bag indicator as the ignition is turned ON.

Does the indicator lamp flash 7 times?

Go to Diagnostic System Check - Vehicle

Go to Step 2

2 |

1. Turn the ignition to LOCK and remove the key.
2. Connect the scan tool to the data link connector (DLC).
3. Turn ON the ignition.
4. Request the SIR DTC display with the scan tool.

Is the same DTC displayed that occurred when the Diagnostic System Check - Vehicle was previously performed?

Go to Step 3

Go to Diagnostic Trouble Code (DTC) List - Vehicle

3 |

1. Clear the SIR DTCs.
2. Turn OFF the ignition for at least 30 seconds.
3. Observe the air bag indicator as the ignition is turned ON.

Does the indicator lamp flash 7 times?

System OK

Go to Step 4

4 |

1. Turn the ignition to LOCK and remove the key.
2. Disconnect the sensing and diagnostic module (SDM) connector.
3. Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
4. Connect the SDM connector and ensure that all components are properly mounted.

Did you complete the action?

Go to Diagnostic System Check - Vehicle

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