C2122

C2122-T-CASE/DIFFERENTIAL SWITCH SUPPLY VOLTAGE CIRCUIT LOW





For a complete wiring diagram refer to diagrams.
^ When Monitored:
With the ignition on and no system undervoltage or overvoltage condition present.
^ Set Condition:
The Final Drive Control Module detects that the Drivetrain Sensor Supply voltage is below 4.75 volts for 300 mS.

Possible Causes

- INTERMITTENT T-CASE/DIFFERENTIAL SWITCH SUPPLY VOLTAGE CIRCUIT LOW
- (K77) TRANSFER CASE POSITION SENSE CIRCUIT SHORT TO GROUND
- (T537) LOCKER SWITCH SUPPLY CIRCUIT SHORT TO GROUND
- TRANSFER CASE SELECTOR SWITCH
- AXLE LOCK SWITCH
- FINAL DRIVE CONTROL MODULE

Diagnostic Test
1. TRANSFER CASE POSITION SENSE VOLTAGE EQUAL TO 0 VOLTS





Turn the ignition on. Measure the voltage of the Transfer Case Position Sense circuit by backprobing the Transfer Case Position Sensor harness connector.

Is the voltage equal to 0 volts?
Yes >>Go to 2
No >>Go to 7

2. TRANSFER CASE POSITION SENSOR





Turn the ignition off.
Disconnect the Transfer Case Position Sensor harness connector.
Turn the ignition on.
Measure the voltage of the (K77) Transfer Case Position Sense circuit at the Transfer Case Position Sensor harness connector.

Is the voltage above 4.75 volts?
Yes >>Replace the Transfer Case Position Sensor in accordance with the Service Information.
Perform the FDCM VERIFICATION TEST.
No >>Go to 3

3. AXLE LOCK SWITCH





Turn the ignition off.
Disconnect the Axle Lock Switch harness connector.
Turn the ignition on.
Measure the voltage of the (T537) Locker Switch Supply circuit at the Axle Lock Switch harness connector.

Is the voltage above 4.75 volts?
Yes >>Replace the Axle Lock Switch in accordance with the Service Information.
Perform the FDCM VERIFICATION TEST.
No >>Go to 4

4. (K77) TRANSFER CASE POSITION SENSE CIRCUIT SHORT TO GROUND





Turn the ignition off.
Disconnect the Final Drive Control Module harness connector.
Measure the resistance between the (K77) Transfer Case Position Sense circuit at the Transfer Case Position Sensor harness connector and ground.

Is the resistance below 5.0 ohms?
Yes >>Repair the (K77) Transfer Case Position Sense circuit for a short to ground.
Perform the FDCM VERIFICATION TEST.
No >>Go to 5

5. (T537) LOCKER SWITCH SUPPLY CIRCUIT SHORT TO GROUND





Measure the resistance between the (T537) Locker Switch Supply circuit at the Axle Lock Switch harness connector and ground.

Is the resistance below 5.0 ohms?
Yes >>Repair the (T537) Locker Switch Supply circuit for a short to ground.
Perform the FDCM VERIFICATION TEST.
No >>Go to 6

6. FINAL DRIVE CONTROL MODULE
View repair.

Repair
Replace the Final Drive Control Module in accordance with the Service information.
Perform the FDCM VERIFICATION TEST.
7. INTERMITTENT WIRING AND CONNECTORS
The conditions necessary to set this DTC are not present at this time.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
While monitoring the scan tool data relative to this circuit, wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.

Were any problems found?
Yes >>Repair as necessary.
Perform the FDCM VERIFICATION TEST.
No >>Test complete.