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Coolant temp problem

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mudbog42

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My temperature guage is not reading the temp:mad: , I get a check engine light 14 which states coolant temperature is too high:confused: , on my scanner, it shows the coolant temp at 320 and doesn't change. I know the temperature is not 320 because it hasn't even warmed up.:doah:

Just changed out the sending unit, is there a way to check out what is wrong with this, I would like to have my engine temperature guage working again

Thanks ahead of time:bow: :bow:
 
Coolant temp and temperature gauge use two different senders.

If your scanner is showing 320, I believe that means the wire/sender is fully grounded. (either that or not grounded at all, can't recall which)

Which sending unit did you replace? If you did the one in the head, that's the wrong one. Leave your scanner hooked up, truck off key on, temperature reading, and disconnect the intake mounted 2 wire temp sender. Then jumper the two terminals in the connector. If the temp changes on the scanner from very hot to very cold, then you know the sender is the issue.
 
I changed the one on the manifold with a connecter and two wires connected to it. Not sure what you want me to jump. But when I disconnected it completely, now the scanner reads -4
 
Just put a jumper wire between the two terminals on the connector. That will just ensure there is nothing wrong with the wiring. It should read "full hot". If it does, your sender is bad.

If the wiring was screwed up, it wouldn't matter what you did, the temp to the ECM likely wouldn't change.

I guess theoretically the idiot light switches are two wire, if the connectors were ever the same (I really doubt it) the store could have sold you the wrong sender.
 
ok jumped the connecter and it read full hot, disconnected and -4, so I guess I'm on my way back to the parts store,
Thanks for the help
 
whatever you do, don't use any extra sealant on the sender when you install it or it won't work correctly. There should already be some sort of sealant on the sender that is special. If you use teflon tape or the like it will keep the sender from grounding properly and GM uses ground to activate items.
 
Well take the tape off and reinstall it and see if that does the trick.
 
Yupp you were absolutely right, I took the tape off and now its working again yay....thanks so much because my next sensor would probably have done the same thing after I would have put more tape on it
Thanks again
 
No problem. Just keep that in mind when installing any kind of sensor on a GM vehicle. GM uses ground to activate everything and the tape interferes with the path to ground.
 
Yeah I will definitly remember that next time, but now the scanner is reading correctly, but my gauge still isn't moving, is there a way to test the gauge or that printed circuit behind the cluster???
 
Basically same deal. Disconnect sender in head, then ground the wire, watch that the gauge goes full hot/full cold. If it doesn't, wiring or gauge issue, if it does, temp sender.
 
Ok the one on the left of the gauge goes full hot when grounded and the one on the right just keeps blowing the gage/idle fuse when I try it
 
Do you have an aftermarket gauge or something? I'm not understanding the lingo, there is only one wire you mess with at the head...
 
oh yeah sorry, no the gauge is stock, but I have my dash apart right now also. When taking the connector off at the temp sender and grounding each side the guage does nothing.

But behind the guage in the dash there is three connections. With a multimeter the one on the left and right read 12v and the top 0 so I'm guessing the top is the ground. Now if I ground the screw on the left back of the gauge it will read full hot, but if I try it on the other side, it just blows the fuse
 
Put your cluster/gauge back in place, and do it from the sender wire.

You are blowing the fuse because you are shorting the power supply to the gauge cluster to ground.
 
from the sender wire on the manifold right, off of the sensor I just replaced. There is two wires off of that sender unit, unless I'm checking a different one, I grounded both of those and the gauge does nothing
 
No, that's the wrong one. Temperature GAUGE uses a single wire sender, drivers side head, roughly between cylinders 1 and 3.
 
The coolant temp sensor located in the intake manifold is for the ECM, the engine temp sensor located in the driver side head between the 1-3 cylinders is for the temp guage in the dash. The engine temp sensor should have a single green wire going to it. Ground the green wire and the guage should peg full hot, when the wire is not grounded the guage should drop to cold.
 
Ok yeah I tried that one too actually, when I grounded out the one wire from the sender, the gauge did absolutely nothing.
 
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