DTC 71

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 DIET, GREASE, ETC. FROM THE MOUNTING SURFACE.
- POSITION THE SDM HORIZONTALLY ON THE MOUNTING SURFACE.
- POINT THE ARROW ON THE SDM TOWARD THE FRONT OF THE VEHICLE.
- 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.

CAUTION: BEFORE PERFORMING DIAGNOSTICS, THE IGNITION SWITCH MUST BE IN THE "OFF" POSITION FOR 10 MINUTES (REFER TO DISABLING AND ENABLING PRECAUTIONS).

NOTICE: When DTC 18 or DTC 24 has been set, it is necessary to replace the Sensing and Diagnostic Module (SDM). Setting DTC 18 or 24 will also cause DTC 71 to set. When a Scan tool "Clear Codes" command is issued and the malfunction is still present, diagnostic trouble codes 18, 24 and 71 will remain current. Ensure that the short to ground condition is repaired prior to installing a replacement SDM to avoid damaging the SDM.

NOTICE: Perform "SIR DIAGNOSTIC SYSTEM CHECK" before proceeding with this chart. SIR Diagnostic System Check

IMPORTANT: Always replace any SDM with DTC 71 after repairing all other DTCs.

CIRCUIT DESCRIPTION
DTC 71 is an indication of a potential internal SDM malfunction and will set if any of the following conditions are detected:
1. VLR voltage out of normal operating range. (Approximately 23 volts.)
2. 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 18).
3. 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 24).
4. The voltage measured at "Driver Side LO" and "Passenger Side LO" are less than three volts.
5. Crash data recording reserved voltage discharge time failure for three consecutive ignition cycles.
6. The calculated checksum for internal memory does not match the store value.
7. The sensing device inside the SDM which converts vehicle velocity changes to an electrical signal is malfunctioning.
8. The driver current source and/or passenger current source is malfunctioning.
9. The temporary memory storage area is malfunctioning.
10. SDM is unable to read from or write to Electrically Erasable Programmable Read Only Memory (EEPROM).
11. 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.
12. There is a Micro Processor energy reserve time failure.

DTC WILL SET WHEN:
Any of the indicated malfunctions are detected by the SDM. The malfunctions are tested at different times:
1. "Turn-On" and "Continuous Monitoring"
2. "Turn-On"
3. "Continuous Monitoring"
4. "Current Source Diagnostics"
5. Asynchronously

ACTION TAKEN:
SDM turns On the AIR BAG telltale lamp and sets DTC 71. DTC 71 may or may not be latched with DTC 18 or 24.

DTC WILL CLEAR WHEN:
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 71 is latched with DTC 18 or 24, it is critical to diagnose those DTCs before replacing the SDM. If DTC 71 returns after the SDM has been replaced, make sure that "Driver Side LO" and "Passenger Side LO" are not less than three volts.