Pinpoint Test R: DTC P187A:00

Electronic Locking Differential (ELD) System

Pinpoint Test R: DTC P187A:00



Normal Operation

When the Mode Select Switch (MSS) is engaged into either 4H or 4L mode to lock the rear differential, a Pulse Width Modulated (PWM) signal is sent to the Electronic Locking Differential (ELD) field coil by the Transfer Case Control Module (TCCM) through the differential lock control circuit. This signal is a PWM (Pulse Width Modulated) signal which 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. If after a set period time the differential does not lock, the TCCM (Transfer Case Control Module) sets this code indicating low TCCM (Transfer Case Control Module) system voltage.

- DTC P187A:00 Transfer Case Control Module System Voltage Low - Rear Locking Differential Disabled: No Sub Type Information- The TCCM (Transfer Case Control Module) senses the system voltage below 11.5 volts at the differential lock control circuit. The ELD (Electronic Locking Differential) is disabled until locker switch is disengaged and re-engaged or for the remainder of the ignition cycle

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- TCCM (Transfer Case Control Module)

PINPOINT TEST R : DTC P187A:00

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

R1 CHECK FOR DTCs

NOTE: Failure to place the Mode Select Switch (MSS) 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 Mode Select Switch (MSS) in 2H (vehicles equipped with Electronic Shift-On-The-Fly (ESOF) system) or OFF (vehicles equipped with 2-Wheel Drive (2WD) system).

- Enter the following diagnostic mode on the scan tool: Self-Test- TCCM (Transfer Case Control Module).

Are any DTCs present?

Yes
If only DTC P187A:00 is retrieved, GO to R2.

For any other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Electronic Locking Differential (ELD) System
No
IDENTIFY the customer concern and GO to Symptom Chart - Four-Wheel Drive (4WD) System Electronic Locking Differential (ELD) System.

R2 CHECK BATTERY CONDITION

- Ignition OFF.

- Carry out the Battery Condition Test. Pinpoint Tests

Does the battery pass the condition test?

Yes
If the battery passed the condition test but required a recharge, REFER to Charing System to diagnose the charging system. CLEAR all CMDTCs (Continuous Memory Diagnostic Trouble Codes). TEST the system for normal operation. REPEAT the self-test.

If the battery passed the condition test and did not require a recharge, GO to R3.

No
INSTALL a new battery. CLEAR all CMDTCs (Continuous Memory Diagnostic Trouble Codes). TEST the system for normal operation. REPEAT the self-test.

R3 CHECK THE CHARGING SYSTEM VOLTAGE

NOTE: Do not allow the engine rpm to increase above 2,000 rpm while carrying out this step or the generator may self excite and result in default charging system output voltage. If engine rpm has gone above 2,000 rpm, turn the vehicle OFF and restart the engine before carrying out this step.

- Start the engine.

- Measure the voltage of the battery.
- Turn on headlights and HVAC fan on high, run engine at 1,500 rpm for a minimum of 2 minutes.






Is the battery voltage between 13-15.2 volts?

Yes
GO to R4.

No
REFER to Charging System to diagnose the charging system. CLEAR all CMDTCs (Continuous Memory Diagnostic Trouble Codes). TEST the system for normal operation. REPEAT the self-test.

R4 CHECK THE TCCM (Transfer Case Control Module) SUPPLY VOLTAGE (VBAT_4X4) PID

- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).

Is the VBAT_4X4 PID greater than 12 volts?

Yes
GO to R5.

No
REFER to Charging System to DIAGNOSE the low battery voltage and/or charging system concern.

R5 CHECK RESISTANCE OF THE ELD (Electronic Locking Differential) FIELD COIL

- Ignition OFF.

- Disconnect: ELD (Electronic Locking Differential) Field Coil C4359.

- NOTE: If the temperatures are exceptionally high, a higher than normal resistance reading can result. A lower temperature can 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 R6.

No
INSTALL a new ELD (Electronic Locking Differential) field coil. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.

R6 CHECK THE ELD (Electronic Locking Differential) FIELD COIL GROUND

- Measure the resistance between ELD (Electronic Locking Differential) field coil C4359-2, circuit GD176 (BK/WH), harness side and ground.





Is the resistance less than 5 ohms?

Yes
GO to R7.

No
REPAIR circuit GD176 (BK/WH). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.

R7 CHECK FOR CORRECT TCCM (Transfer Case Control Module) OPERATION

- Ignition OFF.

- Disconnect all TCCM (Transfer Case Control Module) connectors.

- Check for:
- corrosion

- pushed-out pins


- Connect all TCCM (Transfer Case Control Module) connectors and 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. REPEAT the self-test.

No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.