Pinpoint Test C: P187A, P187C: 00 And P187D: 00
- Refer to Wiring Diagrams Two Wheel Drive/Four Wheel Drive Systems
for schematic and connector information.
Normal Operation and Fault Conditions
When the ELDMSS is engaged to lock the rear differential, the TCCM sends a PWM signal to the ELD field coil through the differential lock control circuit. This PWM signal is initially 98% duty cycle to lock the differential and then tapers off to a lower duty cycle once the differential is locked. If the differential lock control circuit is open or shorted to ground, the TCCM senses a signal is not reaching the differential and sets a DTC.
DTC Fault Trigger Conditions
DTC Description Fault Trigger Condition TCCM P187A: 00 Transfer Case Control Module System Voltage Low - Rear Locking Differential Disabled: No Sub Type Information This DTC sets when the TCCM senses the differential lock control circuit low voltage. The ELD differential is not engaged. TCCM P187C: 00 Differential Lock-Up Control Circuit/Open: No Sub Type Information This DTC sets when the TCCM senses the differential lock control circuit is open. The ELD differential is not engaged. TCCM P187D: 00 Differential Lock-Up Control Circuit Low: No Sub Type Information This DTC sets when the TCCM senses the differential lock control circuit is shorted to ground. The ELD differential is not engaged. Possible Sources
- Wiring, terminals or connectors
- TCCM
- NOTE: Make sure the battery is fully charged before carrying out this pinpoint test.
- C1 CHECK FOR TCCM (TRANSFER CASE CONTROL MODULE) DTC (DIAGNOSTIC TROUBLE CODE)S
- Ignition ON.
- Set the ELDMSS to OFF.
- Enter the following diagnostic mode on the scan tool: TCCM Self-Test.
Are any DTCs present?
Yes For DTC P187C: 00, GO to C4 For DTC P187D: 00, GO to C2 For all other DTCs, REFER to the Diagnostic Trouble Code (DTC) Chart . No VERIFY the customer concern and GO to the Symptom Chart. - C2 CHECK FOR TCCM (TRANSFER CASE CONTROL MODULE) DTC (DIAGNOSTIC TROUBLE CODE)S WITH THE ELD (ELECTRONIC LOCKING DIFFERENTIAL) FIELD COIL DISCONNECTED
- Ignition OFF.
- Disconnect ELD Field Coil C4359.
- Ignition ON.
- Set the ELDMSS to OFF.
- Enter the following diagnostic mode: TCCM Self-Test.
CLEAR the DTCs. REPEAT the self-test. Does DTC P187D: 00 return?
Yes GO to C3 No INSTALL a new ELD field coil. REFER to: Differential Carrier - Vehicles With: Electronic Locking Differential (ELD) . CLEAR the DTCs. - C3 CHECK THE ELD (ELECTRONIC LOCKING DIFFERENTIAL) DIFFERENTIAL LOCK CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect TCCM C2371B.
- Measure:
Positive Lead Measurement / Action Negative Lead C2371B-6 Ground
Is the resistance greater than 10, 000 ohms?
Yes GO to C4 No REPAIR the circuit. - C4 CHECK THE ELD (ELECTRONIC LOCKING DIFFERENTIAL) DIFFERENTIAL LOCK CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect TCCM C2371B.
- Disconnect ELD Field Coil C4359.
Is the resistance less than 3 ohms?
Yes GO to C5 No REPAIR the circuit. - C5 CHECK FIELD COIL GROUND CIRCUIT
- Measure:
Positive Lead Measurement / Action Negative Lead C4359-2 Ground
Is the resistance less than 3 ohms?
Yes GO to C6 No REPAIR the circuit. - Measure:
- C6 CHECK FOR CORRECT TCCM (TRANSFER CASE CONTROL MODULE) OPERATION
- Ignition OFF.
- Disconnect and inspect all TCCMconnectors.
- Check for the Following:
- Connect all TCCMconnectors. Make sure they seat and latch 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) . . 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.