C1400

C1400-TRANSFER CASE RANGE SELECT SWITCH PERFORMANCE





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 is not receiving a valid voltage for any switch position.

Possible Causes

- INTERMITTENT TRANSFER CASE RANGE SELECT SWITCH PERFORMANCE
- (K77) TRANSFER CASE POSITION SENSE CIRCUIT OPEN
- (K77) TRANSFER CASE POSITION SENSE CIRCUIT SHORTED TO GROUND
- (T525) TRANSFER CASE RETURN CIRCUIT OPEN
- (T525) TRANSFER CASE RETURN CIRCUIT SHORT TO GROUND
- TRANSFER CASE POSITION SENSOR
- FINAL DRIVE CONTROL MODULE

Diagnostic Test
1. DTC IS ACTIVE Ignition on, engine not running.

NOTE: Repair any system undervoltage or overvoltage DTCs that are set in this module before proceeding. With the scan tool, select View DTCs in the Final Drive Control Module.

Is the status Active for this DTC?
Yes >>Go To 2
No >>Go To 9

2. (K77) TRANSFER CASE POSITION SENSE CIRCUIT VOLTAGE





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.

Is the voltage between 4.7 and 5.2 volts?
Yes >>Go To 5
No >>Go To 3

3. (K77) TRANSFER CASE POSITION SENSE CIRCUIT OPEN





Turn the ignition off.
Disconnect the Final Drive Control Module harness connector.
Measure the resistance of the (K77) Transfer Case Position Sense circuit.

Is the resistance greater than 5.0 ohms?
Yes >>Repair the (K77) Transfer Case Position Sense circuit for an open.
Perform the FDCM VERIFICATION TEST.
No >>Go To 4

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





Measure the resistance between the (K77) Transfer Case Position Sense circuit and ground.

Is the resistance less than 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 8

5. TRANSFER CASE POSITION SENSOR





Ignition on, engine not running.
With the scan tool in Data Display, read the 4wd Range Switch Voltage with the Transfer Case Position Sensor harness connector disconnected.
The switch voltage should be approximately 0 volts.
Turn the ignition off.
Connect a jumper wire between the (K77) Transfer Case Position Sense circuit and the (T525) Transfer Case Return circuit in the Transfer Case Position Sensor harness connector.
Ignition on, engine not running.
With the scan tool in Data Display, read the 4wd Range Switch Voltage.
The switch voltage should be approximately 5 volts.

Does the voltage display as described?
Yes >>Replace the Transfer Case Position Sensor.
Perform the FDCM VERIFICATION TEST.
No >>Go To 6

6. (T525) TRANSFER CASE RETURN CIRCUIT OPEN





Turn the ignition off.
Disconnect the Final Drive Control Module harness connector.
Measure the resistance of the (T525) Transfer Case Return circuit between the Transfer Case Position Sensor harness connector and the Final Drive Control Module harness connector.

Is the resistance above 5.0 ohms?
Yes >>Repair the (T525) Transfer Case Return circuit for an open.
Perform the FDCM VERIFICATION TEST.
No >>Go To 7

7. (T525) TRANSFER CASE RETURN CIRCUIT SHORT TO GROUND





Measure the resistance between the (T525) Transfer Case Return circuit and ground.

Is the resistance less than 5.0 ohms?
Yes >>Repair the (T525) Transfer Case Return circuit for a short to ground.
Perform the FDCM VERIFICATION TEST.
No >>Go To 8

8. FINAL DRIVE CONTROL MODULE
View repair.

Repair
Replace the Final Drive Control Module in accordance with the Service Information.
Perform the FDCM VERIFICATION TEST.
9. INTERMITTENT TRANSFER CASE RANGE SELECT SWITCH PERFORMANCE
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.
While monitoring the scan tool data relative to this circuit, move the selector switch to each position several times.
Look for the data to change other than as expected or for the DTC to reset.

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