Pinpoint Test B: Four-Wheel Drive (4WD) Clutch Field Coil - Electrical
- Refer to FOUR WHEEL DRIVE SYSTEMS
for schematic and connector information.
Normal Operation and Fault Conditions
When the transfer case is in 4A and 4H modes, the TCCM provides a PWM voltage to the transfer case clutch field coil. The energized field coil moves a ball and ramp cam to engage a clutch as necessary to provide torque to the front axle.
The TCCM4WD clutch field coil driver monitors the circuit for open circuit, short to power, and short to ground. If an electrical fault is detected, the TCCM will store a DTC.
DTC Fault Trigger Conditions
DTC Description Fault Trigger Condition TCCM P1825:00 4-Wheel Drive Clutch Relay Open Circuit: No Sub Type Information This DTC sets when TCCM detect an open circuit. The TCCM disables transfer case clutch operation. TCCM P1826:00 4-Wheel Drive Low Clutch Relay Circuit To Battery: No Sub Type Information This DTC sets when TCCM detect a short to voltage. Transfer case clutch operation, though disabled by the TCCM, is fully engaged when this DTC is present. TCCM P1827:00 4-Wheel Drive Low Clutch Relay Circuit To Ground: No Sub Type Information This DTC sets when TCCM detect a short to ground. The TCCM disables transfer case clutch operation. Possible Sources
- Clutch control circuit short to ground
- Clutch control open circuit
- Clutch control circuit short to voltage
- Clutch control ground open circuit
- Clutch field coil
- B1 CHECK FOR TCCM (TRANSFER CASE CONTROL MODULE) DTC (DIAGNOSTIC TROUBLE CODE)
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TCCMKOEO Self-Test.
Are any DTCs present?
Yes For DTC P1825:00, GO to B3. For DTC P1826:00, GO to B4. For DTC P1827:00, GO to B2
For all other DTC's, the DTC chart: TCCM.No The 4WD clutch field coil is electrically sound at this time. - B2 CHECK CLUTCH CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect Transfer Case C1290 .
- Disconnect TCCM C2371B .
- Measure:
Positive Lead Measurement / Action Negative Lead C1290-2 Ground
Is the resistance greater than 10, 000 ohms?
Yes GO to B3 No REPAIR the short to ground. - B3 CHECK CLUTCH CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect Transfer Case C1290 .
- Disconnect TCCM C2371B .
Is the resistance less than 3 ohms?
Yes GO to B4 No REPAIR the open circuit. - B4 CHECK CLUTCH CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect Transfer Case C1290 .
- Disconnect TCCM C2371B .
- Ignition ON.
- Measure:
Positive Lead Measurement / Action Negative Lead C1290-2 Ground
Is any voltage present?
Yes REPAIR the short to voltage. No GO to B5 - B5 CHECK CLUTCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect Transfer Case C1290 .
- Measure:
Positive Lead Measurement / Action Negative Lead C1290-1 Ground
Is the resistance less than 3 ohms?
Yes CHECK OASIS for any applicable service articles: TSB, GSB, SSM, or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new transfer case clutch coil. No REPAIR the open circuit.