Pinpoint Test AC: DTC P187C:00 and P187D:00
Electronic Locking Differential (ELD) System
Pinpoint Test AC: DTC P187C:00 and P187D:00
Normal Operation
When the MSS (Mode Select Switch) is engaged to lock the rear differential, a PWM (Pulse Width Modulated) signal is sent to the ELD (Electronic Locking Differential) field coil by the TCCM (Transfer Case Control Module) through the differential lock control circuit. This PWM (Pulse Width Modulated) signal is initially 98% duty cycle to lock the differential and decreases to 40% duty cycle once the differential is locked. If the differential lock control circuit is open or shorted to ground, the TCCM (Transfer Case Control Module) senses a signal is not reaching the differential and sets a DTC.
- DTC P187C:00 (Differential Lock-Up Control Circuit/Open: No Sub Type Information)- The TCCM (Transfer Case Control Module) sends a signal to the differential to lock the differential. The TCCM (Transfer Case Control Module) C2371B pin 9 senses that the differential lock control circuit is open. The ELD (Electronic Locking Differential) differential is not engaged.
- DTC P187D:00 (Differential Lock-Up Control Circuit Low: No Sub Type Information)- The TCCM (Transfer Case Control Module) sends a signal to lock the differential. The TCCM (Transfer Case Control Module) C2371B pin 9 senses that the differential lock control circuit is shorted to ground. The ELD (Electronic Locking Differential) differential is not engaged.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- TCCM (Transfer Case Control Module)
PINPOINT TEST AC : DTC P187C:00 AND P187D:00
NOTE:
Make sure the battery is fully charged before carrying out this pinpoint test.
AC1 CHECK FOR TCCM (Transfer Case Control Module) DTCs
NOTE: Failure to place the MSS (Mode Select Switch) in 2H or OFF prior to carrying out a self-test of the TCCM (Transfer Case Control Module) (to disable the ELD (Electronic Locking Differential) field coil) results in inaccurate self-test.
- Ignition ON.
- Set the MSS (Mode Select Switch) in 2H (ESOF (Electronic Shift-On-The-Fly) or 2 speed-torque-on-demand).
- Set the MSS (Mode Select Switch) in OFF (2WD (2-Wheel Drive) ).
- Enter the following diagnostic mode on the scan tool: Self-Test- TCCM (Transfer Case Control Module).
Are any DTCs present?
Yes
For DTC P187C:00, GO to AC4.
For DTC P187D:00, GO to AC2.
For all other DTCs, REFER to the TCCM (Transfer Case Control Module) DTC Chart Electronic Locking Differential (ELD) System.
No
IDENTIFY the customer concern and GO to Symptom Chart - Electronic Locking Differential (ELD) System. Symptom Chart - Electronic Locking Differential (ELD) System
AC2 CHECK FOR TCCM (Transfer Case Control Module) DTCs WITH THE ELD (Electronic Locking Differential) FIELD COIL DISCONNECTED
- Ignition OFF.
- Disconnect: ELD (Electronic Locking Differential) Field Coil.
- Ignition ON.
- Set the MSS (Mode Select Switch) in 2H (ESOF (Electronic Shift-On-The-Fly) or 2 speed-torque-on-demand).
- Set the MSS (Mode Select Switch) in OFF (2WD (2-Wheel Drive) ).
- Enter the following diagnostic mode on the scan tool: Self-Test- TCCM (Transfer Case Control Module).
CLEAR the DTCs. REPEAT the self-test. Does DTC P187D:00 return?
Yes
GO to AC3.
No
INSTALL a new field coil. CLEAR the DTCs. TEST the system for normal operation.
AC3 CHECK THE ELD (Electronic Locking Differential) DIFFERENTIAL LOCK CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: TCCM (Transfer Case Control Module) C2371B.
- Measure the resistance between TCCM (Transfer Case Control Module) C2371B-9, circuit CCF31 (BN/VT), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to AC4.
No
REPAIR circuit CCF31 (BN/VT). CLEAR the DTCs. TEST the system for normal operation.
AC4 CHECK THE ELD (Electronic Locking Differential) DIFFERENTIAL LOCK CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: TCCM (Transfer Case Control Module) C2371B.
- Disconnect: ELD (Electronic Locking Differential) Field Coil.
- Measure the resistance between TCCM (Transfer Case Control Module) C2371B-9, circuit CCF31 (BN/VT), harness side and ELD (Electronic Locking Differential) field coil C4359-1, circuit CCF31 (BN/VT), harness side.
Is the resistance less than 3 ohms?
Yes
GO to AC5.
No
REPAIR circuit CCF31 (BN/VT). CLEAR the DTCs. TEST the system for normal operation.
AC5 CHECK FOR CORRECT TCCM (Transfer Case Control Module) OPERATION
- Ignition OFF.
- Disconnect and inspect all TCCM (Transfer Case Control Module) connectors.
- Repair:
- 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 (Transfer Case Control Module) connectors. Make sure they are seated correctly.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new TCCM (Transfer Case Control Module). REFER to Transfer Case Control Module (TCCM) . TEST the system for normal operation.
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.