Pinpoint Test AA: DTC P185C:00
Electronic Locking Differential (ELD) System
Pinpoint Test AA: DTC P185C: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. When the differential is fully locked, the indicator will illuminate steady.
- DTC P185C:00 (Differential Lock-Up Indicator Circuit High: No Sub Type Information)- When the driver engages the ELD (Electronic Locking Differential) the TCCM (Transfer Case Control Module) C2371A-20 senses the indicator circuit has high voltage and is not illuminated.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- TCCM (Transfer Case Control Module)
PINPOINT TEST AA : DTC P185C:00
NOTE:
Make sure the battery is fully charged before performing this pinpoint test.
AA1 OPERATE THE ELD (Electronic Locking Differential) INDICATOR USING THE TCCM (Transfer Case Control Module) REAR LOCKING DIFF LAMP OUTPUT CONTROL OPTIONAL (DIFF_LAMP_OS) PID
- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).
- Command the DIFF_LAMP_OS PID on.
Does the ELD (Electronic Locking Differential) indicator in the MSS (Mode Select Switch) illuminate?
Yes
GO to AA5.
No
GO to AA2.
AA2 CHECK THE ELD (Electronic Locking Differential) INDICATOR CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Disconnect: MSS (Mode Select Switch).
- Ignition ON.
- Measure the voltage between TCCM (Transfer Case Control Module) C2371A-20, circuit CCF33 (GY/YE), harness side and ground.
Is any voltage present?
Yes
REPAIR circuit CCF33 (GY/YE). CLEAR the DTCs. TEST the system for normal operation.
No
GO to AA3.
AA3 CHECK FOR VOLTAGE TO THE MSS (Mode Select Switch)
- Measure and record the battery voltage at the battery.
- Measure the voltage between MSS (Mode Select Switch) C284-7, circuit CBP34 (VT/BN), harness side and ground.
Does the voltage equal the recorded battery voltage?
Yes
GO to AA4.
No
VERIFY BCM (Body Control Module) fuse 34 (10A) is OK. If OK, REPAIR circuit CBP34 (VT/BN). If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short [1][2]Diagrams By Number.
CLEAR the DTCs. TEST the system for normal operation.
AA4 CHECK THE TCCM (Transfer Case Control Module) GROUND CIRCUIT
- Ignition OFF.
- Disconnect: TCCM (Transfer Case Control Module) C2371B.
- Measure the resistance between C2371B-3, circuit GD123 (BK/GY), harness side and ground.
Is the resistance less than 3 ohms?
Yes
GO to AA5.
No
REPAIR circuit GD123 (BK/GY). CLEAR the DTCs. TEST the system for normal operation.
AA5 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.