C1408

C1408- TRANSFER CASE BRAKE CONTROL CIRCUIT HIGH





When Monitored:
Ignition on. Battery voltage between 9 and 16 volts.

Set Condition:
FCM detects high voltage for 0.5 seconds on the Transfer Case Brake Control Circuit with the feature ON

Possible Causes
- INTERMITTENT CONDITION
- (T300) SHIFT MOTOR BRAKE SIGNAL CIRCUIT SHORTED TO VOLTAGE
- (T300) SHIFT MOTOR BRAKE SIGNAL CIRCUIT OPEN
- SHIFT MOTOR/MODE SENSOR ASSEMBLY
- POWER DISTRIBUTION MODULE
- FRONT CONTROL MODULE

Theory of Operation
The purpose of the Shift Motor Brake is to provide a means of physically holding the Transfer Case actuator in place. The Shift Motor Brake consists of a solenoid which releases the Transfer Case actuator when current is applied.

The FCM applies a ground to the Shift Motor Brake to release the Transfer Case actuator:
1. Any time a shift is taking place.
2. For a predetermined amount of time before and after the shift based on a timer.
3. Any time a Shift Motor Brake DTC is active.

No shifting will take place if either a Shift Motor Brake DTC is present or the Shift Motor Brake timer is active. While the timer is active, or if a Shift Motor Brake short to ground DTC is present, static braking is implemented to keep the actuator in place

Diagnostic Test
1. SHIFT MOTOR BRAKE DTC IS ACTIVE





Note: This DTC indicates that the FCM has detected high voltage on the Shift Motor Brake Signal circuit while the Shift Motor Brake was released by the FCM during a shift. Carefully inspect the related wiring and connectors for a short to voltage.

Ignition on, engine not running.
With the scan tool, Clear DTCs.
Move the Shift control to each position, while monitoring the Data Display on the scan tool.
Does the DTC reset?
Yes >>Go to 2
No >>Go to 7

2. (T300) SHIFT MOTOR BRAKE SIGNAL CIRCUIT SHORTED TO VOLTAGE





Turn the ignition off.
Disconnect the Shift Motor/Mode Sensor Assembly connector.
Remove the Front Control Module from the Power Distribution Module.
Turn the ignition on.
Measure the voltage of the (T300) Shift Motor Brake Signal circuit at the Shift Motor/Mode Sensor Assembly connector.
Is there any voltage present?
Yes >>Go to 3
No >>Go to 4

3. POWER DISTRIBUTION MODULE





Turn the ignition off.
Disconnect the Power Distribution Module C1 connector.
Turn the ignition on.
Measure the voltage of the (T300) Shift Motor Brake Signal circuit at the Shift Motor/Mode Sensor Assembly connector.
Is there any voltage present?
Yes >>Repair the (T300) Shift Motor Brake Signal circuit for a short to voltage.
Perform the TRANSFER CASE VERIFICATION TEST VER 1. Transfer Case Verification Test
No >>Replace the Power Distribution Module in accordance with the Service information.
Perform the TRANSFER CASE VERIFICATION TEST VER 1.

4. (T300) SHIFT MOTOR BRAKE SIGNAL CIRCUIT OPEN





Measure the resistance of the (T300) Shift Motor Brake Signal circuit.
Is the resistance above 5.0 ohms?
Yes >>Repair the (T300) Shift Motor Brake Signal circuit for an open.
Perform the TRANSFER CASE VERIFICATION TEST VER 1.
No >>Go to 5

5. SHIFT MOTOR/MODE SENSOR ASSEMBLY





Turn the ignition off.
Reconnect the disconnected FCM C3 connector.
Connect one end of a jumper to the (T300) Shift Motor Brake Signal circuit.
While monitoring the T-Case Brake State on the scan tool, momentarily connect the other end of the jumper to ground.
Does the T-Case Brake State change from Off to On when the jumper wire is connected to ground.
Yes >>Replace the Shift Motor/Mode Sensor Assembly.
Perform the TRANSFER CASE VERIFICATION TEST VER 1.
No >>Go to 6

6. FRONT CONTROL MODULE
View repair.
Repair
Replace the Front Control Module in accordance with the Service information.

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 TRANSFER CASE VERIFICATION TEST- VER 1.
No >>Test complete.