ECM Coolant Temp Sensor (Page 1/2)
Gene1000 AUG 18, 06:22 PM
Hello all,
After some effort, I was able to get to the ECM coolant temperature sensor on my ‘87 Fiero GT. But it’s the original and seems to be frozen in place. Exerting a lot of force on a standard ratchet hasn’t worked and I’m concerned that I may break it while it’s still in place.
Then I’d really be stuck.

There is no way I can get an impact wrench in. I’ve squirted some “liquid wrench” in the cavity and I’m letting it sit. I’m concerned that I may break the sensor while it’s still in place.

Can these sensors take a lot of torque? Am I safe in using a large torque bar to try to free it loose?

Any suggestions?

Thanks all.

Gene
Cherry Hill, NJ
USA
Patrick AUG 18, 06:54 PM

Why are you trying to remove it?

If you already know it's faulty, why are you worried about breaking it?

It's a pipe thread, so it'll be tight, but it will unscrew. I hope you've moved the EGR solenoid out of the way prior to doing this.

For anyone who's never accessed this sensor, I found a video Here that shows a few things.
steve308 AUG 18, 08:49 PM
I've been down the path you are currently on......Under search look for "code 15". Don't be concerned if the bushing that the sensor screws into comes out, it's a common bushing availabe at lowes, home depot etc. I ended up needing a new ecm to finally solve the issue (code 15) . Below is my last update

Hopefully last update. 125 miles today with no issues. For those who may run into a code 15, parts I used were. Standard motor products TX3 temp sensor, Dorman 85100 pigtail, 1/2 - in mip x 3/8-in fip reduction bushing (lowes 977204) and last but not least a Cardone remanufactured computer and of course the assistance of the brain trust here on Pennocks.
Vintage-Nut AUG 18, 08:59 PM
It needs a deep 19mm socket.

IF the reducer fitting comes out with the sensor, no big deal; put the fitting in a vise, then remove the sensor from the fitting...

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

Gene1000 AUG 19, 01:27 AM
Thanks for your input, guys.

Patrick, yes, I moved out the EGR unit and its mounting bracket.
To answer your question, my concern is exerting so much effort to remove the sensor that it cracks or warps and as a result it becomes impossible to remove.
The video you referenced seems to show the fan sensor, not the CTS. The video below is the one I found that depicts the arrangement on my ‘87 GT.

https://youtu.be/u4fqYc7ih3c?si=Jwd6EVaBPixytWYd

The engine runs poorly on a cold startup. After it gets warm, it runs better. As you know, the coolant temperature sensor, CTS, lets the ECM know and when the engine is cold, the ECM will adjust fuel mixture and timing accordingly so it runs properly. So I want to replace it as a possible cause.

Steve, I scanned the codes and nothing came up. So I replaced the MAP sensor and TPS sensor anyway. Next comes the CTS and spark plugs.
Haven’t checked vacuum yet. I’m familiar with the bushing and I’ll see what happens.

Vintage, thanks for your suggestion on the fitting.
I’ll try removing the sensor again tomorrow. If I can somehow use an impact driver, I’ll do so. But it’s very tight down there.

Thanks again, guys.
Gene
1985 Fiero GT AUG 19, 01:41 AM

quote
Originally posted by Gene1000:

The video you referenced seems to show the fan sensor, not the CTS. The video below is the one I found that depicts the arrangement on my ‘87 GT.

https://youtu.be/u4fqYc7ih3c?si=Jwd6EVaBPixytWYd




Hey, what do you know, that's my dad haha, I'll tell him his video is still helping people, he seems suspiciously self sufficient doing this 6 years ago, now that I'm old enough to be doing car stuff, he requires more help haha.
Patrick AUG 19, 02:15 AM

quote
Originally posted by Patrick:

For anyone who's never accessed this sensor, I found a video Here that shows a few things.




quote
Originally posted by Gene1000:

The video you referenced seems to show the fan sensor, not the CTS. The video below is the one I found that depicts the arrangement on my ‘87 GT.

https://yout...EVaBPixytWYd



Ummm... How is the video you found any different than the one I linked to?



quote
Originally posted by Gene1000:

The video you referenced seems to show the fan sensor, not the CTS.



Not a chance.

Me thinks you might have things in the wrong location. Is your configuration different than what is shown below?




quote
Originally posted by Gene1000:

The engine runs poorly on a cold startup. After it gets warm, it runs better. As you know, the coolant temperature sensor, CTS, lets the ECM know and when the engine is cold, the ECM will adjust fuel mixture and timing accordingly so it runs properly. So I want to replace it as a possible cause.

Steve, I scanned the codes and nothing came up. So I replaced the MAP sensor and TPS sensor anyway. Next comes the CTS and spark plugs. Haven’t checked vacuum yet.



So you're just throwing parts at it.

Not only is it a waste of money replacing totally functional older parts, but quite often, the new parts are defective right out of the box!

You also can't rely on "the codes" telling you if a sensor needs replacement. Sometimes, the sensor has degenerated enough to negatively affect engine performance, but it's not bad enough to set a code.

As we tell so many people new to Fieros and to this forum, get a scanner and/or something like WinALDL on there and see what's actually going on with your engine.

PFF member Paul Romsky has recently marketed what you need. Save yourself time and money... and order that device.

[This message has been edited by Patrick (edited 08-19-2025).]

Gene1000 AUG 19, 04:54 AM
Patrick- thanks for the information.

Very strange. When I first clicked on your link, it took me here a number of times.

https://youtube.com/shorts/...?si=8mgutdsVm99NWhbK

He’s replacing the fan switch, not the coolant temperature sensor. But now when I click on your latest link, it takes me to a different video where this time David Cook is indeed replacing the CTS. The video is the same one I linked to earlier. Strange indeed. Could be my phone or the YouTube web site or something else.

In any case, in your diagram the CTS is at the bottom…..which is exactly the one I’m working on. The location is correct.

I don’t look at this as “throwing parts at it” because I wanted to do it whether the codes show a problem or not. I enjoy working on the car. I’m actually going to replace the TPS whether I need it or not. I could care less about the 50 bucks. You look at it as a “waste of money” whereas I look at it as fun and educational. To each our own.

But I think I’m going to take you up on the ALDL monitoring tool. I’m currently on Windows 11. Hopefully the software will wonk on that system. If not, I have older machines. So thanks for the suggestion and the link.
Gene1000 AUG 19, 04:57 AM
Oops. “Work”, not “wonk”.
Vintage-Nut AUG 19, 09:18 AM

quote
I don’t look at this as “throwing parts at it”


Yes, some members are very obstinate on their opinions...


quote
I’m actually going to replace the TPS whether I need it or not.


I'm rejuvenating my GT and replaced many 'working' sensors because age, so I understand...


quote
Romsk:
I am the creator of the Fiero GT ALDL Monitor Adapter and GUI that is sold from The Fiero Store (TFS).


Romsk's tool runs only on a PC with Microsoft Windows 7 and up operating systems.
https://www.fierostore.com/...px?s=51419&d=263&p=1