Are there 2 different 3 wire coolant sensors?

I ask because in my 4.9 swap, I finally grounded the wire on the 3 wire coolant sensor that I bought. The ECM reads in the normal range between 100 and 110 C while driving by by 80C my gauge has moved past 260F. What voltage the the gauge send to the sensor because I suspect it's sending 12v instead of 5v which would explain why it's reading more than double. And yes, the C and F designations were intentioal. Recall 212F = 100C.

Interesting thought.

Mine did the same thing. I just switched back to the 2 wire sensor.

quote Originally posted by lou_dias: Are there 2 different 3 wire coolant sensors? I ask because in my 4.9 swap, I finally grounded the wire on the 3 wire coolant sensor that I bought. The ECM reads in the normal range between 100 and 110 C while driving by by 80C my gauge has moved past 260F. What voltage the the gauge send to the sensor because I suspect it's sending 12v instead of 5v which would explain why it's reading more than double. And yes, the C and F designations were intentioal. Recall 212F = 100C.

I have the only three wire part number I've come across in the Northstar. Two pins go to the ECM CTS input and ECM sensor ground. My understanding is that the third pin grounds through the shell, just like the old single pin 12V gauge senders. If you grounded the third wire, then you've grounded the input to your gauge... naturally it will be pegged.

Mine didn't peg at the outset. Just climbed very rapidly and eventually passed the red.

quote Originally posted by Will: I have the only three wire part number I've come across in the Northstar. Two pins go to the ECM CTS input and ECM sensor ground. My understanding is that the third pin grounds through the shell, just like the old single pin 12V gauge senders. If you grounded the third wire, then you've grounded the input to your gauge... naturally it will be pegged.

That's just it though, it "moves" in accordance with the ECM temp, just at a 2.x faster rate. I had the same problem with the TPS where it would read 1.2v at closed throttle instead of .5v because I had 12v going to the TPS instead of 5v and at WOT I'd be at 240% throttle with 66% at idle according to the PCM...

In other words, it doesn't peg and stay pegged as soon as I start the car. The temp gauge moves as the motor warms up.
I wonder if part of the problem is that I am grounding that and the TPS to the strut tower for now instead of back to the PCM...

Did your 4.9 already have a 3 pin CTS in it or did you purchase one?

quote Originally posted by phonedawgz: Did your 4.9 already have a 3 pin CTS in it or did you purchase one?

I purchased one to attempt to run the dash gauge... It's a GM part, just don't know if they made various 3-wire versions...

Any chance you know the part number or the application? If you used one for a S2 3800 SC it should work fine. The gauge temperature curve goes way back to the days where they were drawn out by hand.



If inclined, you might want to check the actual resistance of the sender with the engine warm.

[This message has been edited by phonedawgz (edited 11-19-2012).]

quote Originally posted by lou_dias: Are there 2 different 3 wire coolant sensors? I ask because in my 4.9 swap, I finally grounded the wire on the 3 wire coolant sensor that I bought. The ECM reads in the normal range between 100 and 110 C while driving by by 80C my gauge has moved past 260F. What voltage the the gauge send to the sensor because I suspect it's sending 12v instead of 5v which would explain why it's reading more than double. And yes, the C and F designations were intentioal. Recall 212F = 100C.

Well that is your problem.


The sensor is grounded when you screw it into the block.

3 wires:

The 1st wire feeds the ECM via pin E11 supplies power to the temp sender (and TPS) - 5v if you were wondering. (pin A on the sensor)
The 2nd wire returns to the ECM via pin E16 is the "reading". (pin B on the sensor)
The 3rd wire feeds the Temp gage on the dash via the C500 plug, pin C2. (pin C on the sensor)

Curious as to which wire you grounded?

Got a part #? It's easier to just plug in a new one.
Again, what's weird is that the line going to the ECM is fine, just the gauge is off.

Even though I'm a computer programmer, using a volt/ohm meter is like learning a foreing language and I always as somebody else to do it for me. I can also look up what part number I did buy at Autozone since I would have bought it this summer.

quote Originally posted by lou_dias: Got a part #? It's easier to just plug in a new one. Again, what's weird is that the line going to the ECM is fine, just the gauge is off. Even though I'm a computer programmer, using a volt/ohm meter is like learning a foreing language and I always as somebody else to do it for me. I can also look up what part number I did buy at Autozone since I would have bought it this summer.

Part numbers are listed in my wiring thread:

quote Temp sender (also see NOTE): Located in the thermostat housing (from a 2 wire unit to a 3 wire): use these parts numbers for the correct sender: GM 10096181 AC-Delco 213-815 Borg Warner WT3024 CarQuest TX66 Filko CS-43 GP Sorensen 38-5124 Niehoff DR134TA Napa/Echlin ECHTS4020 Connector comes off a 92 Cavalier or the 3800SC - but most 80-90's GM tps sensor plug will work. pin "A" BLK wire on the switch goes to ecm "E11" pin "B" YEL wire on the switch goes to ecm "E16" pin "C" GRN wire on the switch goes to C500 gage connection

Still have no idea 'what wire you grounded' - if the PCM was always working then it was just a matter of hooking up the gage to the 3rd and last wire via the C500 connector.

If the gage is off - move the needle.

[This message has been edited by Mickey_Moose (edited 11-19-2012).]

Like Lou... My ECM was also reading the correct temperature.
My gauge, OTOH, started out "normal" and then went to "scream" as the engine warmed up.

Well, if my PCM reads right and my gauge moves as the car warms up, I grounded the ground wire.

I should have pre-faced this with: this was originally a Fiero Factory conversion...

[This message has been edited by lou_dias (edited 11-19-2012).]

Delco #10096181

http://www.rockauto.com/cat...305403&parttype=4748

I believe I have the right switch. I think the problem is electrical. For some reason, I am getting 12v to the TPS again. I think what I need to do is make sure the 5v grounds go back the the PCM instead of the chasis.