2001 Monte Carlo ss with a 3.8 liter motor in great condition. The problem is... check engine light on, Temperature gauge not working and cooling fans stay on for 5 minutes after turning car off.

So I took it to autozone.. p0118... ETC (engine temp control ) There are 2.. I changed them both and changed Thermostat.. I disconnected battery to clear code.. cleared...no CEL while driving.. Then turn car off... upon restart CEL comes on and fans continue to run for 5 minutes extra again after I turn off car... SUMMARY... CEL, Fans running unnecessarily, Temp gauge not working............Solution Relay maybe????

First, thank you for your help. Still not resolved unfortunately. As I said, I replaced the ETC and the engine coolant level sensor on radiator just below cap and the thermostat also with no success. New information is the following... when I start the car I sometimes get a loud whining (like pressure equalizing ) I shut it off and it whines down just like pressure releasing. The car runs great, I cannot detect anything in its operation just no temperature gauge, CEL and cooling fans run. I am stuck as to what the issue may be.

  • Have you checked the coolant level and or temp sensors?
    – mikes
    Nov 21, 2013 at 2:40
  • @mikes - "ETC (engine temp control ) There are 2.. I changed them both and changed Thermostat"
    – cinelli
    Nov 21, 2013 at 6:23
  • When the ECT is cold, the sensors internal resistance is high. When the ECT's increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively low ECT signal voltage, which is a high temperature indication, DTC P0117 sets. With a multimeter, check the resistance of the sensor cold, and then observe it as the car warms up. Even if the sensor isn't working observe the sensor to make sure of it's functonality.
    – cinelli
    Nov 21, 2013 at 8:31
  • Did you checked/clean up the connectors between the sensor and PCM? You may have a bad cable or faulty connectors. Feb 3, 2014 at 15:25

2 Answers 2


The ECU can measure 3 primary sensors in the cooling system. Engine thermostat for the engine temperature, the engine coolant temperature tracks this. You can also have a temperature sensor for water temperature into the radiator and a temperature sensor for water temperature out of the radiator. The radiator sensors decide the plausibility of the radiator cooling the cooling system. If the plausibility check of radiator is out of spec the cooling fans are commanded to run, to avoid the sysytem overheating. P0118 indicates a high voltage in the ECT circuit, usually means resistance in the circuit, a disconnection, a thermostat staying open causing an over-cool coolant system, or a failed ECT sensor. P0117 indicates a low voltage in the circuit, usually works out as short in the system, or a failed ECT sensor.


this is a design feature of some thermo fans as another contributor mentioned.If it really annoys you any auto sparky can install a manual override switch on your dash.I would advise using a switch incorporating an on/off light.I turn mine off on cold days to bring engine to operating temp. a.s.a.p.Sooner auto choke is off more fuel you save

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