Circuit Description
The ignition switch supplies Ignition 1 voltage to the inflatable restraint sensing and diagnostic module (SDM) at terminal A1 using the SDM Fuse. The ignition switch also supplies Ignition 1 voltage to the instrument cluster at terminal A13 using the IPC Fuse. The AIR BAG warning lamp is controlled by the SDM via Class 2 serial data. When the ignition switch is first turned to the ON position, the SDM responds by performing tests on the SIR system and then commanding the AIR BAG warning lamp OFF after it has flashed seven times. If IGNITION 1 is outside of the normal operating voltage range (9 volts-16 volts), the AIR BAG warning lamp will stay ON with no DTCs set.
Diagnostic Aids
The loss of serial data communication between the SDM and the instrument cluster will cause the AIR BAG warning lamp to stay ON. Refer to Diagnostic System Check - Data Link Communications in Data Link Communications.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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This step checks to see if the AIR BAG warning lamp flashes seven times when the ignition key is turned to the ON position.
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This step checks to see if DTC U1088 is present in the instrument cluster.
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This step checks to see if the AIR BAG warning indicator is being commanded ON.
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This step checks to see if the ignition voltage to the SDM is more than 9 V.
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This step determines if the ignition voltage to the SDM is more than 16 V or if there is a malfunctioning SDM.
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This step checks to see if the SDM wiring harness connector is corroded or damaged.
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This step determines if there is an open or a high resistance in CKT 1139 or if there is a high resistance in the power feed circuit to the SDM Fuse.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System check performed? | -- | ||
2 | Was the Instrument Cluster Indicator System Check performed? | -- | Go to Indicator System Check in Instrument Panel, Gauges and Console | |
Does the AIR BAG warning lamp flash seven times? | -- | |||
4 | Replace the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console. Is the repair complete? | -- | -- | |
Is DTC U1088 set? | -- | Go to Diagnostic System Check - Data Link Communications in Data Link Communications | ||
Use the scan tool to request the instrument cluster display list. Is the AIR BAG warning lamp being commanded ON? | -- | |||
Is the ignition voltage displayed on the scan tool more than the specified value? | 9 V | |||
Is the ignition voltage displayed on the scan tool more than the specified value? | 16 V | Go to Battery Is Undercharged or Overcharged in Engine Electrical | ||
Is the SDM wiring harness connector corroded or damaged? | -- | |||
10 | Replace the SDM wiring harness connector. Refer to Wiring Repair . Is the repair complete? | -- | -- | |
Is the measured resistance within the specified value? | 0-2 ohms | |||
12 |
Is the repair complete? | -- | -- | |
13 |
Is the repair complete? | -- | -- | |
14 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Is the replacement complete? | -- | -- | |
15 | Reconnect all SIR and instrument cluster components, making sure that all components are properly reconnected and properly mounted. Have all SIR and instrument cluster components been properly reconnected and properly mounted? | -- | -- |
