Lincoln Navigator Manuals

Lincoln Navigator: Transmission Cooling / Transmission Cooling. Diagnosis and Testing

Lincoln Navigator 2018-2025 Workshop Manual / Automatic Transmission / Transmission Cooling / Transmission Cooling. Diagnosis and Testing

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices.
REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).

Inspection and Verification

NOTICE: When internal wear/damage occurs in the transmission, metal particles and clutch plate material can travel into the torque converter and the transmission fluid heat exchanger. These contaminants are a major cause of recurring transmission concerns. To prevent future concerns, remove these contaminants from the cooling system before placing the transmission back into use. Refer to the transmission fluid cooler backflushing and cleaning procedure.

  1. Verify the customer concern by operating the vehicle to duplicate the condition.
  1. Visually inspect for obvious signs of mechanical or electrical damage.
  1. If the inspection reveals obvious concerns that can be readily identified, repair as necessary.
  1. Install new components if a transmission fluid leak is found in any of the transmission cooling components.
  1. If the cause is not visually evident, check for diagnostic trouble codes (DTCs). Refer to the DTC Chart.
  1. If no diagnostic trouble codes (DTCs) are present, verify the symptom and refer to the Symptom Chart.

Diagnostic Trouble Code (DTC) Chart

Module DTC Description Action
PCM P0218:00 Transmission Fluid Temperature Sensor 'A' Over Temperature Condition: No Sub Type Information GO to Pinpoint Test A
PCM P2681:00 Engine Coolant Bypass Valve 'A' Control Circuit/Open: No Sub Type Information GO to Pinpoint Test B
PCM P2682:00 Engine Coolant Bypass Valve 'A' Control Circuit Low: No Sub Type Information GO to Pinpoint Test B
PCM P2683:00 Engine Coolant Bypass Valve 'A' Control Circuit High: No Sub Type Information GO to Pinpoint Test B
TCM P1783:00 Transmission Overtemperature Condition: No Sub Type Information GO to Pinpoint Test A

Symptom Chart

  Symptom Chart


Condition Actions
Transmission overheating   GO to Pinpoint Test C
Transmission fluid leak   GO to Pinpoint Test D
Engine coolant in the transmission fluid   GO to Pinpoint Test E

Pinpoint Tests


PINPOINT TEST A: P0218, P1783

Normal Operation and Fault Conditions

The TCM monitors transmission fluid temperature using the TFT sensor in the transmission sump area. If the temperature exceeds a threshold, it sets a DTC . The TCM will communicate an over temperature condition to the PCM , which will also set a DTC and limit powertrain torque to prevent further overheating.

DTC Fault Trigger Conditions

DTC Description Fault Trigger Condition
PCM P0218:00 Transmission Fluid Temperature Sensor 'A' Over Temperature Condition: No Sub Type Information This DTC indicates the PCM detected a transmission fluid over temperature condition. This DTC will limit powertrain torque to prevent further overheating.
TCM P1783:00 Transmission Overtemperature Condition: No Sub Type Information This DTC indicates the transmission fluid temperature was greater than 275°F (135°C) for more than 5 seconds.

Possible Sources

  • TFT sensor circuit fault
  • Transmission fluid heater coolant control valve
  • Transmission overheating condition
A1 CHECK FOR TFT (TRANSMISSION FLUID TEMPERATURE) SENSOR CIRCUIT DIAGNOSTIC TROUBLE CODES (DTCS)
  • Using a diagnostic scan tool, carry out the TCM self-test.

Are any TFT sensor circuit diagnostic trouble codes (DTCs) present?
Yes RESOLVE all TFT sensor circuit diagnostic trouble codes (DTCs) first.
REFER to: DTC Chart and Pinpoint Tests - 3.5L EcoBoost (272kW/370PS) (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Diagnosis and Testing).
No GO to A2

A2 CHECK FOR TRANSMISSION FLUID HEATER COOLANT CONTROL VALVE DIAGNOSTIC TROUBLE CODES (DTCS)
  • Using a diagnostic scan tool, carry out the PCM self-test.

Are diagnostic trouble codes (DTCs) P2681, P2682, and/or P2683 present?
Yes RESOLVE those diagnostic trouble codes (DTCs) first. GO to Pinpoint Test B
No To diagnose an overheating concern, GO to Pinpoint Test C

PINPOINT TEST B: TRANSMISSION FLUID HEATER COOLANT CONTROL VALVE

Refer to Wiring Diagrams Cell 25 for schematic and connector information.

Normal Operation and Fault Conditions

The transmission fluid heater coolant control valve is an electrically controlled solenoid that allows or bypasses the flow of engine coolant through the transmission fluid heat exchanger. This electrically controlled valve is normally open when not energized. The valve receives fused battery voltage when the ignition is in the run or start position and is grounded by the PCM via a low side driver. The PCM monitors the solenoid and circuits for electrical faults and sets an appropriate DTC .

DTC Fault Trigger Conditions

DTC Description Fault Trigger Condition
PCM P2681:00 Engine Coolant Bypass Valve 'A' Control Circuit/Open: No Sub Type Information This DTC indicates an open circuit in the transmission fluid heater coolant control valve circuit.
PCM P2682:00 Engine Coolant Bypass Valve 'A' Control Circuit Low: No Sub Type Information This DTC indicates an open circuit or a short to ground in the transmission fluid heater coolant control valve circuit.
PCM P2683:00 Engine Coolant Bypass Valve 'A' Control Circuit High: No Sub Type Information This DTC indicates a short to power in the transmission fluid heater coolant control valve circuit.

Possible Sources

  • Connectors damaged or pushed-out terminals, corrosion, loose wires and missing or damaged seals
  • Circuit open or shorted
  • BJB fuse F8
  • Transmission fluid heater coolant control valve
  • PCM
B1 RETRIEVE AND RECORD ALL DIAGNOSTIC TROUBLE CODES (DTCS)
  • Using a diagnostic scan tool, carry out the PCM self-test.

Is DTC P2681, P2682, or P2683 present?
Yes GO to B2
No The system is operating correctly at this time. The concern may have been caused by a loose connector.

B2 CHECK THE TRANSMISSION FLUID HEATER COOLANT CONTROL VALVE POWER CIRCUIT FOR VOLTAGE
  • Disconnect Transmission fluid heater coolant control valve C1702 .
  • Inspect the connector for damaged or pushed out terminals.
  • Ignition ON.
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C1702-1   Ground

Is the voltage greater than 11 volts?
Yes GO to B3
No CHECK BJB fuse F8.
If the fuse is OK, REFER to the Wiring Diagrams manual to identify and repair an open circuit.
If the fuse is not OK, REFER to the Wiring Diagrams manual to identify and repair a short to ground.

B3 CHECK THE TRANSMISSION FLUID HEATER COOLANT CONTROL VALVE CONTROL CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Disconnect PCM C175T .
  • Inspect the connector for damaged or pushed out terminals.
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C1702-2   C175T-76

Is the resistance less than 3 ohms?
Yes GO to B4
No REPAIR the open circuit.

B4 CHECK THE TRANSMISSION FLUID HEATER COOLANT CONTROL VALVE CONTROL CIRCUIT FOR A SHORT TO GROUND
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C1702-2   Ground

Is the resistance greater than 10,000 ohms?
Yes GO to B5
No REPAIR the short to ground.

B5 CHECK THE TRANSMISSION FLUID HEATER COOLANT CONTROL VALVE CONTROL CIRCUIT FOR A SHORT TO POWER
  • Ignition ON.
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C1702-2   Ground

Is any voltage present?
Yes INSTALL a new transmission fluid heater coolant control valve.
REFER to: Transmission Fluid Heater Coolant Control Valve (303-03 Engine Cooling - 3.5L EcoBoost (272kW/370PS), Removal and Installation).
No REPAIR the short to power.

PINPOINT TEST C: TRANSMISSION OVERHEATING

Normal Operation and Fault Conditions

  • Damaged transmission fluid heat exchanger
    • Inspect the transmission fluid heat exchanger for damage and leaks. INSTALL new components as necessary. REFER to: Transmission Fluid Heat Exchanger (307-02 Transmission Cooling, Removal and Installation).
  • Excessive vehicle or towing loads, severe vehicle use
    • Refer to the Owner's Literature for more information on vehicle load, GVW and trailer towing.
  • Incorrect transmission fluid level
    • Check the transmission fluid level. ADJUST the transmission fluid level as necessary. REFER to: Transmission Fluid Level Check (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, General Procedures).
  • Transmission fluid condition
    • Collect a transmission fluid sample and inspect it for debris or contamination. REFER to: Preliminary Inspection (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Diagnosis and Testing).
  • Engine overheating
    • Check the engine cooling system for proper operation. REFER to: Cooling Fan Control (303-03 Engine Cooling - 3.5L EcoBoost (272kW/370PS), Diagnosis and Testing).
      REFER to: Engine Cooling (303-03 Engine Cooling - 3.5L EcoBoost (272kW/370PS), Diagnosis and Testing).
      REFER to: Engine Temperature (303-03 Engine Cooling - 3.5L EcoBoost (272kW/370PS), Diagnosis and Testing).
  • Transmission cooling system clogged or restricted
    • Carry out the Transmission Fluid Cooler Backflushing and Cleaning procedure. If transmission fluid cooling system flow is low after backflushing, INSTALL new components as necessary. REFER to: Transmission Fluid Cooler - Backflushing and Cleaning (307-02 Transmission Cooling, General Procedures).
  • Transmission fluid heater coolant control valve malfunctioning
    • INSTALL a new transmission fluid heater coolant control valve. REFER to: Transmission Fluid Heater Coolant Control Valve (303-03 Engine Cooling - 3.5L EcoBoost (272kW/370PS), Removal and Installation).
  • Internal transmission concerns
    • Resolve any transmission performance diagnostic trouble codes (DTCs) or symptoms, especially those related to the TCC or clutch applications. REFER to: DTC Chart and Pinpoint Tests - 3.5L EcoBoost (272kW/370PS) (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Diagnosis and Testing).
      REFER to: Diagnosis By Symptom (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Diagnosis and Testing).
    • Inspect the internal transmission components for wear or damage. Check all clutches and bearings for signs of overheating. INSTALL new components as necessary. REFER to: Transmission (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Overhaul).

Possible Sources

  • Damaged or restricted transmission fluid heat exchanger
  • Incorrect transmission fluid level or condition
  • Transmission fluid heater coolant control valve
  • Internal transmission components
Diagnostic steps are not provided for this symptom or DTC.  REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).
PINPOINT TEST D: TRANSMISSION FLUID LEAK

Normal Operation and Fault Conditions

  • Transmission fluid heat exchanger
    • Check the transmission fluid heat exchanger for leaks. Inspect the exchanger inlet and outlet, and the exchanger element. INSTALL a new transmission fluid heat exchanger as necessary. REFER to: Transmission Fluid Heat Exchanger (307-02 Transmission Cooling, Removal and Installation).
  • Transmission seals and gaskets
    • If the transmission cooling system is not the source of the leak, check the transmission for leaking seals and gaskets. REFER to: Leakage Inspection (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Diagnosis and Testing).

Possible Sources

  • Transmission fluid heat exchanger
  • Transmission seal or gasket
Diagnostic steps are not provided for this symptom or DTC.  REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).
PINPOINT TEST E: ENGINE COOLANT IN THE TRANSMISSION FLUID

Normal Operation and Fault Conditions

  • Transmission fluid heat exchanger internal leak
    • INSTALL a new transmission fluid heat exchanger. REFER to: Transmission Fluid Heat Exchanger (307-02 Transmission Cooling, Removal and Installation).
    • Carry out the necessary repairs for a Water in Transmission Fluid concern. REFER to: Preliminary Inspection (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Diagnosis and Testing).
      REFER to: Transmission (307-01 Automatic Transmission - 10-Speed Automatic Transmission – 10R80, Overhaul).

Possible Sources

  • Transmission fluid heat exchanger
Diagnostic steps are not provided for this symptom or DTC.  REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).

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