coolant temperature sensor, sending unit, or gauge?

[mimiddru]

My temperature gauge starting shooting straight up to the highest point with the key at the "on" position and when running. I replaced the coolant temperature sensor, no change. I replaced the coolant temperature sensor again, no change. I replaced the coolant sending unit, change. The gauge no longer shoots straight up. It does; however, go quickly to a quarter up when the key is in the "on" position and when I start the car, it slowly climbs all the way to overheating withing about a minute or so. I've also replaced the harness and traced the wires for shorts or bad connections. Couldn't find anything. I'm wondering if the gauge didn't go out of whack from quickly shooting all the way up over and over again before I replaced the sending unit?

[96 SSEi]

hi, maybe something with the dash servo that controls the gauge? when you start the car, do you remember the gauge sweep from zero to max and back again?

[J Wikoff]

Does a 91 have two coolant temp sensors like 92-95 does? One for the pcm and one for the gauge.

[RJolly87]

hi, maybe something with the dash servo that controls the gauge? when you start the car, do you remember the gauge sweep from zero to max and back again?

'91 does not gauge sweep.

I do know that there are two coolant temp signals going on, one for the gauge, one for the PCM, but I can't remember if it's two sensors, or 2 feeds off of the same sender.

[mimiddru]

The gauge slowly climbs all the way up and stays there. It doesn't come back down til I shut off the engine. There's a coolant temperature sensor and a coolant temperature sending unit. It never did that before. It would stay at 0 and slowly climb as the engine warmed up and then stop. Another thing that it has done the last two times I test drove it... it starts fine, idles a little high, drives ok for about five minutes, and then I can't seem to go past second gear. Like it's in a limp mode or something. It's never done this before. It kind of makes me think that there's more going on than a bad temperature gauge in the cluster. I wouldn't think that a bad cluster gauge would influence the car to go into a limp mode, if that is indeed what's happening.

[mimiddru]

*dang*. I traced the wires and just don't know. If I disconnect the sending unit, it just doesn't register anything. If I disconnect the coolant temperature sensor, nothing really changes. I wonder if that means it's the coolant sensor.

[RJolly87]

If it is in your long term plans to do diagnostics and troubleshooting on this car, and you are willing to learn many things about it, it may be a good move to get a scanner that can read live data. That takes much of the guesswork out of many things.

In this case, it could tell you what the actual coolant temperature is according to the pcm, and help you track down which sender is doing what, and help rule out what the problem is.

[SSEBonne4evr]

If it is in your long term plans to do diagnostics and troubleshooting on this car, and you are willing to learn many things about it, it may be a good move to get a scanner that can read live data. That takes much of the guesswork out of many things.

In this case, it could tell you what the actual coolant temperature is according to the pcm, and help you track down which sender is doing what, and help rule out what the problem is.

limited scan apps for this yr. For OBD II you can buy an app for you phone.

[RJolly87]

If it is in your long term plans to do diagnostics and troubleshooting on this car, and you are willing to learn many things about it, it may be a good move to get a scanner that can read live data. That takes much of the guesswork out of many things.

In this case, it could tell you what the actual coolant temperature is according to the pcm, and help you track down which sender is doing what, and help rule out what the problem is.

limited scan apps for this yr. For OBD II you can buy an app for you phone.

Or a bluetooth solution is possible too, however not nearly as popular as the OBD II options.

I have an actron CP9145 myself, and it works great with OBD 1 and OBD 1.5. It will still read some live data on OBD2, as well as codes, but the information seems very limited compared to OBD 1 and 1.5.

[Jrs3800]

There is a single wire sensor for the dash that lives above the exhaust manifold crossover and below the throttle body.. Is this the one you replaced?

[mimiddru]

I did replace that single wire sensor (coolant temperature sender) as well as the coolant temperature sensor. I took the coolant temperature sensor and swapped it out for another one as it was still under warranty. All fix. New coolant temperature sensor was faulty. Duralast.