2001 Temp Guage.

Temp Guage quit working. Now the the cooling fan comes on. No messages. Heat works good. Plenty of coolant. What should I check.

There are a few things it could be:

The thermostat could be stuck open, in which case it would need to be replaced. The signs of an open thermostat would that the engine takes a very long time to heat up and would never get up to normal operating temperature, and your heater would not work ( it may be warm but wouldn't get hot).

The sending unit or gauge could be bad, or it could even be a loose wire that connects them. the sign of one of these problems would be that everything functions normally, except the gauge doesn't move.

All these things can be tested:

To test the thermostat take it out, look at it, (Is it open?) put it in water on the stove, it should open around 195 degrees

To test the wires and gauge, ground the wire to the sending unit with the key on, the gauge should read full scale.

To test the sending unit, according to Haynes:
1. Remove the sending unit from the engine and clip ohmmeter leads to the sending unit body and the terminal. Place the sending unit in a pan of water on the stove, with a cooking thermometer in the water. On a cold (50-80 degrees F) sender, the resistence should be 5,700 to 2,200 ohms. When it has warmed up to operating temperature (170 to 200 degrees F) the resistence should drop to 200-300 ohms.

I had the same problem on my car (2001 Impala). Changed the temp sensor, got the same problem a couple days later, Found out if you pull the PCM fuse, that resets the temp sending unit and haven't had a problem since then. The PCM fuse is under the hood on the passenger side, top fuse box. Pull it out, wait a couple of mins, then put it back in.

I had the same problem.I changed the sending unit and that didnt fix it finally i bought a sending unit that had new wires on it .That was the prob. its been fine since.Mine would work when it was warm out but not when it was cold out.Fix it soon cause the bearings in my elec fans went from running all the time and the fans were a pain in the ass to change.i got them from junkyard for 200 as new ones were over 500.You have to change the whole fan assembly.

Mins stopped working again after about 10 days so i just pulled the pcm fuse ill let you no how it does

Temp Guage quit working. Now the the cooling fan comes on. No messages. Heat works good. Plenty of coolant. What should I check.

I have solved the problem of; intermitent temp gauge function, fans start running when the key is shut off, and AC not working when temp gage quits. There is a GROUND wire above the left (driver's side) headlight under the hood. Remove bolt and the wires, sand the paint away and clean up the wire end. Reinstall the bolt and wire and your problem should be solved..


This drove me crazy for a long time finally solved and needed to share!

I have solved the problem of; intermitent temp gauge function, fans start running when the key is shut off, and AC not working when temp gage quits. There is a GROUND wire above the left (driver's side) headlight under the hood. Remove bolt and the wires, sand the paint away and clean up the wire end. Reinstall the bolt and wire and your problem should be solved..


This drove me crazy for a long time finally solved and needed to share!


Wow. Cool. I'm about to replace the BCM so I will try this when the lady comes home.

We had a police car that had the same problem. You would start it up, the gauge didn't work and the cooling fans would kick in non-stop. Well i remember reading on here about disconnecting the battery. I tried it for the first time and it kept doing the same thing. I tried it again leaving the battery disconnected for about five minutes. After starting and running it, it was fine. I left a note in there for the next officer in there to watch for the symptoms. This car is usually ran all day and all night with approximately 88900 miles on it. It's about about a week since it happened and i haven't heard anything yet. I will keep you guys posted....:)

Mike