Pinpoint Test B : DTC P187C:00 And P187D:00
- Refer to Four Wheel Drive Systems
for schematic and connector information.
Normal Operation and Fault Conditions
When the ELDMSS is engaged to lock the rear differential, the TCCM sends a PWM signal to the ELD field coil through the differential lock control circuit. This PWM signal is initially 98% duty cycle to lock the differential and then tapers off to a lower duty cycle once the differential is locked. If the differential lock control circuit is open or shorted to ground, the TCCM senses a signal is not reaching the differential and sets a DTC.
DTC Fault Trigger Conditions
DTC Description Fault Trigger Condition TCCM P187C:00 Differential Lock-Up Control Circuit/Open: No Sub Type Information This DTC sets when the TCCM senses the differential lock control circuit is open. The ELD differential is not engaged. TCCM P187D:00 Differential Lock-Up Control Circuit Low: No Sub Type Information This DTC sets when the TCCM senses the differential lock control circuit is shorted to ground. The ELD differential is not engaged. Possible Sources
- Wiring, terminals or connectors
- TCCM
- NOTE: Make sure the battery is fully charged before carrying out this pinpoint test.
- B1 CHECK FOR TCCM DTCS
- Ignition ON.
- Set the ELDMSS to OFF.
- Enter the following diagnostic mode: TCCM Self-Test.
Are any DTCs present?
Yes For DTC P187C:00, GO to B4. For DTC P187D:00, GO to B2 For all other DTCs, REFER to the DTC Chart: TCCM. No VERIFY the customer concern and GO to the Symptom Chart. - B2 CHECK FOR TCCM DTCS WITH THE ELD FIELD COIL DISCONNECTED
- Ignition OFF.
- Disconnect ELD Field Coil C4359.
- Ignition ON.
- Set the ELDMSS to OFF.
- Enter the following diagnostic mode: TCCM Self-Test.
CLEAR the DTCs. REPEAT the self-test. Does DTC P187D:00 return?
Yes GO to B3 No INSTALL a new ELD field coil. REFER to: Differential Carrier - Vehicles With: Electronic Locking Differential (ELD) . REFER to: Differential Carrier - Vehicles With: Electronic Locking Differential (ELD) . CLEAR the DTCs. - B3 CHECK THE ELD DIFFERENTIAL LOCK CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect TCCM C2371B.
- Measure:
Positive Lead Measurement / Action Negative Lead C2371B-9 Ground
Is the resistance greater than 10, 000 ohms?
Yes GO to B4 No REPAIR the circuit. - B4 CHECK THE ELD DIFFERENTIAL LOCK CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect TCCM C2371B.
- Disconnect ELD Field Coil C4359.
Is the resistance less than 3 ohms?
Yes GO to B5 No REPAIR the circuit. - B5 CHECK FIELD COIL GROUND CIRCUIT
- Measure:
Positive Lead Measurement / Action Negative Lead C4359-2 Ground
Is the resistance less than 3 ohms?
Yes GO to B6 No REPAIR the circuit. - Measure:
- B6 CHECK FOR CORRECT TCCM OPERATION
- Ignition OFF.
- Disconnect and inspect all TCCM connectors.
- Check for the following:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary
- Connect all TCCM connectors. Make sure they seat and latch correctly.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes INSTALL a new TCCM. REFER to: Transfer Case Control Module (TCCM) . No The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. ADDRESS the root cause of the connector or pin issues.