Temp sensor malfunction?

Asked by Aug 23, 2017 at 03:37 PM about the 1998 Pontiac Trans Sport 4 Dr Montana Passenger Van

Question type: Maintenance & Repair

I have a 1998 Pontiac Transport Montana. Recently the check engine light
came on and the van overheated / has been overheating. The problem, I
think, has to do with the radiator fans. They don't turn on when the engine
reads hot.

I believe that the temperature gauge is working correctly. When I'm idled at a
light, the temperature slowly creeps up. When I start driving the temperature
slowly goes down.

I've read other questions on the forum  that deal with this sort of problem but
MY question is; if the temperature gauge is working correctly is the
temperature sensor still potentially at fault?

I would think that the component that tells the fans to kick on is the same
part that tells the gauge what to display.


9 Answers


hello..when you are going down the road the incoming air is your fan...so, you need to go to pepboys,autozone,checkers and get the fan temp switch..they can also tell you where its at...


also..have you put 12 volts/ground to the fan???


How about testing those fans? It is simple. 2 wires with alligator clips. Unhook the negative battery terminal. Unhook the fan from pigtail. Put a wire on each terminal of fan and touch one on battery negative and one on battery positive. Fan should run immediately. Doesn't matter about polarity they will run backwards or forwards. With the age of that car you are probably looking at dead fan motors

1 people found this helpful.

I will check the fans as my next step then


Obviously if fans work, plug in fan pigtails before reconnecting negative battery terminal.

1 people found this helpful.

Fans both work...


Have you had the system and cap pressure tested? How old is coolant? 5 years or more is too old. 50/50 mix? How old is thermostat? Any air in the system? Your radiator if original might not be dissipating heat as it should and might be somewhat filled with gunk and sediment. Head gasket leak? Pressure test will confirm that. Leaks? Pressure test will again confirm. Do not use tap water to mix your concentration of antifreeze. Use distilled water. Unless you buy it already mixed.


You can test that CTS


The computer turns on the radiator cooling fans. On some vehicles there's a coolant temperature sensor, for the computer, and a separate coolant temperature sending unit for the gauge on the dash. What trouble codes do you have? The engine overheating shouldn't trigger the check engine light. Unless, for example, a coil pack or something burned out because of the overheating. If you find that the cooling fans work, unplug the coolant temperature sensor and start the engine. The check engine light will be on because the sensor is unplugged. Ignore it. The cooling fans should immediately come on at high speed with the sensor unplugged. HTH. -Jim

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