For 1990-2009 cars

### Circuit Description

DTC B1071 is an indication of a potential internal SDM malfunction and will set if any of the following conditions are detected:

• | The VLR voltage is out of normal operating range. (Approximately 23 volts)

• | The voltage measured at "Driver Side LO" is greater than three volts, and the voltage measured at "Passenger Side LO" is less than or equal to three volts, (DTC B1018).

• | The voltage measured at "Driver Side LO" is less than or equal to three volts, and the voltage measured at "Passenger Side LO" is greater than three volts, (DTC B1024).

• | The voltage measured at "Driver Side LO" and "Passenger Side LO" are less than three volts.

• | Crash data recording reserved voltage discharge time failure for three consecutive ignition cycles.

• | The calculated checksum for internal memory does not match the store value.

• | The sensing device inside the SDM which converts vehicle velocity changes to an electrical signal is malfunctioning.

• | The driver current source and/or passenger current source is malfunctioning.

• | The temporary memory storage area is malfunctioning.

• | The SDM is unable to read from or write to EEPROM.

• | The voltage measured at "Driver Side LO" and "Passenger Side LO" are greater than or equal to five volts. This indicates that an internal arming sensor is shorted.

• | There is a Micro Processor energy reserve time failure.

### Conditions for Setting the DTC

Any of the indicated malfunctions are detected by the SDM. The malfunctions are tested at different times:

• | "Turn-On" and "Continuous Monitoring

• | "Turn-On"

• | "Continuous Monitoring"

• | "Current Source Diagnostics"

• | Asynchronously

### Action Taken When the DTC Sets

The SDM turns on the AIR BAG telltale lamp and sets DTC B1071. DTC B1071 may or may not be latched with DTC B1018 or DTC B1024.

### Conditions for Clearing the DTC

The malfunction is no longer occurring and the ignition switch is turned OFF, or a scan tool "Clear Codes" command is issued. Some of the indicated malfunctions will only allow the AIR BAG telltale lamp to go out briefly then come back ON. The SDM must be replaced.

### Diagnostic Aids

When DTC B1071 is latched with DTC B1018 or B1024, it is critical to diagnose those DTCs before replacing the SDM. If DTC B1071 returns after the SDM has been replaced, make sure that "Driver Side LO" and "Passenger Side LO" are not less than three volts.

Caution: Be careful when you handle a sensing and diagnostic module (SDM). Do not strike or jolt the SDM. Before applying power to the SDM:

• | Remove any dirt, grease, etc. From the mounting surface.

• | Position the SDM horizontally on the mounting surface.

• | Tighten all of the SDM fasteners and SDM bracket fasteners to the specified torque value.

Failure to follow the correct procedures could cause air bag deployment, personal injury, or unnecessary SIR system repairs.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the SIR Diagnostic System Check? | Go to Step 2 | Go to SIR Diagnostic System Check
2 | Is DTC B1018 also set? | Go to Step 3 | Go to Step 4
3 | Go to DTC B1018. | -- | --
4 | Is DTC B1024 also set? | Go to Step 5 | Go to Step 6
5 | Go to DTC B1024. | -- | --
6 |

1. Turn the ignition switch OFF.
2. Replace the SDM. Refer to "Sensing and Diagnostic Module (SDM)" in this service manual.
3. Repeat the SIR Diagnostic System Check.

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Important: Always replace any SDM with DTC B1071 after repairing all other DTCs.