For 1990-2009 cars

### Circuit Description

When the ignition switch is first turned ON, the SDM will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1", VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM monitors the voltage at "Driver Side LO" terminal A3 and "Passenger Side LO" terminal A4 to detect shorts to B+ or ignition in the inflator module circuits

### DTC Will Set When

The VLR power supply in the SDM is its normal operating voltage range and neither of the two inflator modules is open. Then, if the voltage measured at "Driver Side LO" is greater or equal to five volts, and voltage is measured at "Passenger Side LO" is less than 5 volts for 500 milliseconds during "Continuous Monitoring" or "Current Source Diagnostics" DTC B1025 will set.

• | No "higher priority faults" are detected during "Turn-On."

• | No "higher priority faults" are detected during "Continuous Monitoring."

• | "Ignition 1" voltage is above a specified value.

### Action Taken

SDM turns ON the AIR BAG telltale lamp and sets, DTC B1025. DTC B1025 will take precedence over DTCs B1015, B1016, B1028, B1021 and B1022.

### DTC Will Clear When

The voltage measured at "Driver Side LO" is less than 4 volts for 500 milliseconds during "Continuous Monitoring". Or, the malfunction no longer exists and the ignition is turned OFF.

### Diagnostic Aids

An intermittent condition is likely to be caused by short to B+ or ignition in the driver inflator module circuits. Inspect circuits 347 and 348 carefully for cutting or chafing. If the wiring pigtail of the SIR coil assembly or the driver inflator module is damaged, the component must be replaced.

When measurements are requested in this chart use SA 91114NE DVM with correct terminal adapter from SA 9206Z. When a check for proper connection is requested refer to Intermittent and Poor Connections. When a wire connector or terminal repair is requested, use the proper repair parts and refer to Wiring Repairs .

### DTC Chart Test Description

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

1. This test determines whether the malfunction is occurring in the driver inflator module, coil assembly, or the circuitry.

2. This test checks for a short from "Driver Side HI" to B+ or ignition.

3. This test checks for a short from "Driver Side LO" to B+ or ignition, or an SDM integrity problem.

Step | Action | Yes | No
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1 | Did you perform the Diagnostic System Check - SIR? | Go to Step 2 | Go to SIR Diagnostic System Check
2 |

1. Turn OFF ignition.
2. Disconnect the driver and passenger inflator module, yellow two-way connectors located at the base of the steering column. Leave passenger side connected.
3. Connect SA 9409Z-A SIR driver/passenger load tool to driver and passenger inflator module harness connectors.
4. Turn ON ignition.

Is DTC B1025 current?

Go to Step 4

Go to Step 3

3 |

1. Turn OFF ignition.
2. Remove inflator module from steering wheel. Refer to Driver Inflator Module.
3. Remove and inspect SIR coil and connecting wires for damage. Determine and repair the cause of damage and replace SIR coil. Refer to SIR Coil Assembly.

Go to Step 9

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4 |

1. Turn OFF ignition.
2. Disconnect SIR driver/passenger load tool.
3. Disconnect SDM.
4. Turn ON ignition.
5. Measure voltage on SDM harness connector from terminal A2 to terminal A6 (ground).

Is voltage 1 volt or less?

Go to Step 6

Go to Step 7

5 | Measure resistance from SDM harness connector terminal A3 to terminal A6 (ground). Is voltage 1 ohm or less? | Go to Chart A | Go to Step 8
6 |

1. Turn OFF ignition.
2. Repair short from circuit 347 to B+, or ignition circuit 1139.

Go to Step 8

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7 |

1. Turn OFF ignition.
2. Repair short from circuit 348 to B+, or ignition circuit 1139.

Go to Step 8

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8 |

1. Reconnect all SIR system components. Ensure all components are properly mounted.
2. Clear SIR diagnostic trouble codes.
3. Repeat SIR Diagnostic System Check.

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