Pinpoint Test R: DTC P187A:00
Electronic Locking Differential (ELD) System
Pinpoint Tests
Pinpoint Test R: DTC P187A:00
Refer to Wiring Diagram Set 34, Four-Wheel Drive Systems for schematic and connector information. Diagrams By Number
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 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 continues to send the signal for a set amount of time. If after a set period time the differential does not lock, the TCCM sets this code indicating low TCCM system voltage.
- DTC P187A:00 Transfer Case Control Module System Voltage Low - Rear Locking Differential Disabled: No Sub Type Information - The TCCM senses the system voltage below 11.5 volts at the differential lock control circuit. The ELD 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
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 (to disable the ELD 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.
- 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. Diagnostic Trouble Code Tests and Associated Procedures
No
IDENTIFY the customer concern and GO to Symptom Chart - Four-Wheel Drive (4WD) System Special Tool(s) Used With Diagnostics.
-------------------------------------------------
R2 CHECK BATTERY CONDITION
- Ignition OFF.
- Carry out the Battery Condition Test. Refer to Battery, Mounting and Cables Testing and Inspection. Pinpoint Tests
- Does the battery pass the condition test?
Yes
If the battery passed the condition test but required a recharge, REFER to Charging System Testing and Inspection to diagnose the charging system. CLEAR all CMDTCs. 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. REFER to Battery, Mounting and Cables Battery and Battery Tray. CLEAR all CMDTCs. 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 Testing and Inspection to diagnose the charging system. CLEAR all CMDTCs. TEST the system for normal operation. REPEAT the self-test.
-------------------------------------------------
R4 CHECK THE TCCM SUPPLY VOLTAGE (VBAT_4X4) PID
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Is the VBAT_4X4 PID greater than 12 volts?
Yes
GO to R5.
No
REFER to Charging System Testing and Inspection to DIAGNOSE the low battery voltage and/or charging system concern.
-------------------------------------------------
R5 CHECK RESISTANCE OF THE ELD FIELD COIL
- Ignition OFF.
- Disconnect: ELD 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 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 field coil. REFER to Rear Drive Axle/Differential - Ford 10.50-Inch Ring Gear Service and Repair. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
-------------------------------------------------
R6 CHECK THE ELD FIELD COIL GROUND
- Measure the resistance between ELD 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 OPERATION
- Ignition OFF.
- Disconnect all TCCM connectors.
- Check for:
- corrosion
- pushed-out pins
- Connect all TCCM 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. REFER to Transfer Case Control Module (TCCM) Service and Repair. 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.
-------------------------------------------------