Pinpoint Test AB: DTC P185D:00

Electronic Locking Differential (ELD) System

Pinpoint Test AB: DTC P185D: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 does not lock, the TCCM (Transfer Case Control Module) continues to send the signal for a set amount of time. Once the differential is locked, the indicator will illuminate steady.

- DTC P185D:00 (Differential Lock-up Control Circuit Performance: No Sub Type Information)- The TCCM (Transfer Case Control Module) sends a signal to the lock up solenoid to lock the differential. After several unsuccessful attempts, the TCCM (Transfer Case Control Module) sets this DTC alerting the driver the ELD (Electronic Locking Differential) is inoperative. Fault may be due to a wheel speed condition or due to a mechanical failure within the driveline/axle subsystem.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- ELD (Electronic Locking Differential) field coil

PINPOINT TEST AB : DTC P185D:00

NOTE:
Make sure the battery is fully charged before carrying out this pinpoint test.

AB1 CHECK THE ABS MODULE WHEEL SPEED SENSOR PIDs

- Enter the following diagnostic mode on the scan tool: DataLogger- ABS Module.

- While driving the vehicle at 30 km/h (18 mph), monitor the following wheel speed sensor PIDs:
- Left Front Wheel Speed Sensor (LF_WSPD)
- Left Rear Wheel Speed Sensor (LR_WSPD)
- Right Front Wheel Speed Sensor (RF_WSPD)
- Right Rear Wheel Speed Sensor (RR_WSPD)


- Compare the speedometer reading to the wheel speed sensor PIDs.

Do the wheel speed sensor PIDs and speedometer speeds match within 1.5 km/h (1 mph)?

Yes
GO to AB2.
No
VERIFY that the 4 road wheels are the same size and have similar tread depth. CHECK the ABS for faults. TEST the system for normal operation.

AB2 CHECK RESISTANCE OF THE ELD (Electronic Locking Differential) FIELD COIL

- Ignition OFF.

- Disconnect: ELD (Electronic Locking Differential) Field Coil.

- NOTE: If the temperatures are exceptionally high, a higher than normal resistance reading could result. A lower temperature could result in a lower resistance reading.
Measure the resistance between ELD (Electronic Locking Differential) field coil C4359 pins 1 and 2, component side.







Is the resistance between 2-4 ohms?

Yes
GO to AB3.
No
INSTALL a new ELD (Electronic Locking Differential) field coil. CLEAR the DTCs. TEST the system for normal operation.

AB3 CHECK THE ELD (Electronic Locking Differential) FIELD COIL GROUND

- Measure the resistance between ELD (Electronic Locking Differential) field coil C4359-2, circuit GD123 (BK/GY), harness side and ground.






Is the resistance less than 3 ohms?

Yes
REFER to Differential Assembly &/or Axle Shaft Assembly to repair the rear differential. CLEAR the DTCs. TEST the system for normal operation.
No
REPAIR circuit GD123 (BK/GY). CLEAR the DTCs. TEST the system for normal operation.