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HOMESERVICE MANUALSMERCURY2010MARINER PREMIER, 2.5 7, FWDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - PINPOINT TEST DL: CYLINDER HEAD TEMPERATURE (CHT) SENSOR THROUGH PINPOINT TEST DX: ENGINE COOLANT TEMPERATURE (ECT) SENSOR - (EXCEPT DIESEL & HYBRID)PINPOINT TEST DL: CYLINDER HEAD TEMPERATURE (CHT) SENSORTEST PROCEDURE
2010 Mercury Mariner Premier, 2.5 7, FWD

Test Procedure

2010 Mercury Mariner Premier, 2.5 7, FWDSECTION Test Procedure
  1. DL1 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTCS) 

    Are DTCs P0116, P0119, P0125, P0128, P1116, P1285, P1288, P1289, P128A, P1290, or P1299 present? 

    Yes No
    For DTCs P1116 or P1288, GO to  DL2.
    For KOEO and KOER DTCs P1289 or P1290, GO to  DL8.
    For continuous memory DTCs P0119, P1289, P128A, or P1290, GO to  DL15.
    For KOEO or continuous memory DTC P1299, GO to  DL21.
    For continuous memory DTCs P0125 or P0128, GO to  DL22.
    For continuous memory DTC P0116, GO to  DL24.
    For DTC P1285, GO to  DL18.    		 For temperature warning indicator lamp or gauge (applications with CHT sensor only) symptom, GO to  DL29.
    For all others, GO to DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS .
  2. DL2 SELF-TEST DTCS P1288 OR P1116: CHECK THE COOLING SYSTEM 
    WARNING: TO AVOID PERSONAL INJURY DO NOT UNSCREW THE COOLANT PRESSURE RELIEF CAP WHILE THE ENGINE IS OPERATING OR HOT. THE COOLING SYSTEM IS UNDER PRESSURE. STEAM AND HOT LIQUID CAN COME OUT FORCEFULLY WHEN THE CAP IS LOOSENED SLIGHTLY. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
    • The DTC indicates the temperature sensor is out of self-test range. The engine is not at normal operating temperature.
    • Check the vehicle coolant level.

    Is the cooling system OK? 

    Yes No
    GO to  DL3. REFER to the appropriate Engine Cooling article for loss of coolant diagnosis.
    REPAIR as necessary.
    CLEAR the DTCs. REPEAT the self-test.
  3. DL3 CHECK IF THE VEHICLE ENGINE STARTS 
    • Attempt to start the engine.

    Does the engine start and run normally? 

    Yes No
    GO to  DL6. GO to  DL4.
  4. DL4 CHECK THE RESISTANCE OF THE CHT SENSOR WITH THE ENGINE OFF 
    NOTE: Refer to the chart at the beginning of this test for the resistance specifications.
    • Ignition OFF.
    • CHT Sensor connector disconnected.
    • Measure the resistance between:
      (+) CHT Sensor Connector, Component Side (-) CHT Sensor Connector, Component Side
      CHT SIGRTN

    Is the resistance within specification? 

    Yes No
    GO to  DL5. INSTALL a new CHT sensor.
    REFER to the appropriate Electronic Engine Controls article .
    CLEAR the DTCs. REPEAT the self-test.
  5. DL5 CHECK THE CIRCUIT FROM THE MODULE TO THE COMPONENT 
    NOTE: Refer to the chart at the beginning of this test for the resistance specifications.
    • CHT Sensor connector connected.
    • Ignition ON, engine OFF.
    • Access the PCM and monitor the CHT PID.
    • Using the data collected from the previous step, compare temperature resistance measured at the sensor to the PID temperature voltage measured at the PCM.

    Does the measured value at the sensor agree with measured PID value at the PCM? 

    Yes No
    The concern is elsewhere. RETURN to NO DIAGNOSTIC TROUBLE CODES (DTCS) PRESENT SYMPTOM CHART INDEX , for further direction. GO to  DL12.
  6. DL6 CHECK THE CHT SENSOR OPERATION 
    • Run the engine until the engine temperature stabilizes.
    • Verify the radiator hoses are hot and the cooling system is pressurized.
    • Carry out the PCM self-test.

    Are DTCs P1116 or P1288 present? 

    Yes No
    GO to  DL7. The engine temperature was not stabilized. REPAIR any other DTCs as necessary.
  7. DL7 CHECK THE RESISTANCE OF THE CHT SENSOR 
    NOTE: Refer to the chart at the beginning of this test for the resistance specifications.
    • The vehicle must be at normal operating temperature.
    • Ignition OFF.
    • CHT Sensor connector disconnected.
    • Measure the resistance between:
      (+) CHT Sensor Connector, Component Side (-) CHT Sensor Connector, Component Side
      CHT SIGRTN

    Is the resistance within specification? 

    Yes No
    GO to  DL31. INSTALL a new CHT sensor.
    REFER to the appropriate Electronic Engine Controls article .
    CLEAR the DTCs. REPEAT the self-test.
  8. DL8 DTCS P1289 OR P1290: ACCESS THE CHT PID AND CHECK THE VOLTAGE 
    • Ignition ON, engine OFF.
    • Access the PCM and monitor the CHT PID.

    Is the voltage less than 0.2 V? 

    Yes No
    GO to  DL9. GO to  DL10.
  9. DL9 CHECK FOR A GROUNDED CIRCUIT 
    • CHT Sensor connector disconnected.
    • Ignition ON, engine OFF.
    • Access the PCM and monitor the CHT PID.

    Is the voltage greater than 4.6 V? 

    Yes No
    INSTALL a new CHT sensor.
    REFER to the appropriate Electronic Engine Controls article .
    CLEAR the DTCs. REPEAT the self-test.    		 GO to  DL14.
  10. DL10 CHECK THE CHT CIRCUIT FOR A SHORT TO VOLTAGE 
    • CHT Sensor connector disconnected.
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      (+) CHT Sensor Connector, Harness Side (-)
      CHT Ground

    Is the voltage greater than 5.5 V? 

    Yes No
    REPAIR the short circuit to PWR. CHECK the CHT sensor for damage.
    GO to  DL11.    		 GO to  DL11.
  11. DL11 CHECK THE RESISTANCE OF THE CHT SENSOR WITH THE ENGINE OFF 
    NOTE: Refer to the chart at the beginning of this test for the resistance specifications.
    • Ignition OFF.
    • CHT Sensor connector disconnected.
    • Measure the resistance between:
      (+) CHT Sensor Connector, Component Side (-) CHT Sensor Connector, Component Side
      CHT SIGRTN

    Is the resistance within specification? 

    Yes No
    GO to  DL12. INSTALL a new CHT sensor. REFER to the appropriate Electronic Engine Controls article .
    CLEAR the DTCs. REPEAT the self-test.
  12. DL12 CHECK THE SIGNAL AND SIGRTN CIRCUITS FOR AN OPEN IN THE HARNESS 
    • PCM connector disconnected.
    • Measure the resistance between:
      (+) CHT Sensor Connector, Harness Side (-) PCM Connector, Harness Side
      CHT CHT
      SIGRTN SIGRTN

    Are the resistances less than 5 ohms? 

    Yes No
    GO to  DL13. REPAIR the open circuit. CLEAR the DTCs. REPEAT the self-test.
  13. DL13 CHECK THE SENSOR SIGNAL FOR A SHORT TO VREF 
    • Ignition OFF.
    • PCM connector disconnected.
    • Measure the resistance between:
      (+) PCM Connector, Harness Side (-) PCM Connector, Harness Side
      CHT VREF

    Is the resistance greater than 10K ohms? 

    Yes No
    GO to  DL31. REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test.
  14. DL14 CHECK THE SENSOR SIGNAL FOR A SHORT TO GROUND 
    • Ignition OFF.
    • PCM connector disconnected.
    • Measure the resistance between:
      (+) PCM Connector, Harness Side (-) PCM Connector, Harness Side
      CHT SIGRTN
    • Measure the resistance between:
      (+) PCM Connector, Harness Side (-) 12 Volt Vehicle Battery
      CHT Negative terminal

    Is the resistance greater than 10K ohms? 

    Yes No
    GO to  DL31. REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test.
  15. DL15 DTCS P0119, P1289, P1290 OR P128A: INTERMITTENT CHECK 
    • Ignition ON, engine OFF.
    • Access the PCM and monitor the CHT PID.
    • While observing the PID, carry out the following:
      • tap on the sensor to simulate road shock
      • wiggle the sensor connector

    Is there a large change in the voltage reading? 

    Yes No
    DISCONNECT and INSPECT the connector. If OK, INSTALL a new CHT sensor. REFER to the appropriate Electronic Engine Controls article .
    CLEAR the DTCs. REPEAT the self-test.    		 GO to  DL16.
  16. DL16 CHECK THE ELECTRONIC ENGINE CONTROL (EEC) WIRING HARNESS 
    • Access the PCM and monitor the CHT PID.
    • While observing the PID, wiggle, shake, and bend small sections of the wiring harness while working from the sensor to the PCM.

    Is there a large change in the voltage reading? 

    Yes No
    ISOLATE the concern.
    REPAIR as necessary.
    CLEAR the DTCs. REPEAT the self-test.    		 GO to  DL17.
  17. DL17 CHECK THE PCM AND VEHICLE HARNESS CONNECTORS 
    • PCM connector disconnected.
    • CHT Sensor connector disconnected.

    Are the connectors and terminals OK? 

    Yes No
    GO to  DL31. REPAIR as necessary.
    CLEAR the DTCs. REPEAT the self-test.
  18. DL18 SELF-TEST DTC P1285: EARLY WARNING OF ENGINE OVERHEAT CONDITION 
    WARNING: TO AVOID PERSONAL INJURY DO NOT UNSCREW THE COOLANT PRESSURE RELIEF CAP WHILE THE ENGINE IS OPERATING OR HOT. THE COOLING SYSTEM IS UNDER PRESSURE. STEAM AND HOT LIQUID CAN COME OUT FORCEFULLY WHEN THE CAP IS LOOSENED SLIGHTLY. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.