1659/ FMI 1 THERMOSTAT MONITOR ERROR DETECTED

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Description Thermostat Error Detected
Monitored Parameter Coolant Inlet temperature sensor
Typical Enabling Conditions Always Enabled
Monitor Sequence None
Execution Frequency Once Per Drive Cycle
Typical Duration 30
Dash Lamps MIL
Engine Reaction
Verification Allow Engine to Cool Down Such That Coolant Inlet Temperature is Less Than 50°C (122°F), Drive Vehicle for 30 Minutes, Preferably with a Trailer (Loaded or Unloaded), Do Not Idle Engine Except When Necessary

 

    1. Are any cooling system issues present?
        1. Yes; repair cooling system issues first.

      1. No; Go to step 2.

    1. Check for other fault codes. Is fault code SPN 110/FMI Any or SPN 4193/FMI Any also present?
        1. Yes; diagnose other fault code first.

      1. No; Go to step 3.

To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.

    1. Start engine and bring to operating temperature to 85°C (185°F).

    1. Does engine reach operating temperature 85°C (185°F).
        1. Yes; Go to step 5.

      1. No; replace the engine cooling system thermostat. 

    1. Shut engine OFF.

    1. Disconnect inlet and outlet coolant temperature sensors.

    1. Inspect inlet and outlet coolant temperature sensors, harness connectors for bent, spread or corroded pins.
        1. If pin damage is found, repair as necessary.

      1. If no pin damage is found, Go to step 8.

  1. Check coolant sensor resistance; refer to chart for specifications, replace sensor which is out of range.

    Coolant Sensor Resistance Chart
    Temp °C Temp °F Resistance (Ω) Nominal Resistance Low (Ω) Resistance High (Ω) Nominal Voltage (V) Voltage Low (V) Voltage High (V)
    0 32 5872.8 5496.4 6249.2 2.56 2.51 2.61
    10 50 3769 3640.3 3897.7 2.37 2.33 2.41
    20 68 2480.7 2260.0 2701.4 2.14 2.05 2.22
    30 86 1693.2 1613.4 1773.0 1.89 1.83 1.95
    35 95 1401.1 1338.4 1463.8 1.75 1.69 1.81
    40 104 1166.8 1117.5 1216.1 1.62 1.56 1.67
    50 122 829.5 798.2 860.8 1.36 1.30 1.41
    60 140 593.8 574.5 613.1 1.12 1.07 1.17
    70 158 435.4 423.1 447.7 0.91 0.86 0.95

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