Coolant temp readings going nutzo...

[Fraser]

My coolant temp input is going insane and it correspondingly is making the car run like shite! I think it's been doing this for some time, I just only recently hooked the computer up to actually realize what was going on. I just threw in a new CTS with no change, which it probably needed anyway, I bet the old one was 25 years old. With key/ecu on but not running it seems to show an accurate temp reading, but once the motor is running it goes crazy. I gather there's something from the running engine that's throwing interference into the temp sensor circuit...is there anything in particular I should look for besides ripping apart the wiring to follow it from the sensor to the ecu?

The log shows the same thing the video does, the CLT going batshit.

Here's a link to a video of TS https://drive.google.com/open?id=1qx...fPLh9tY1ucN4Cy
Here's a link to the log file: https://drive.google.com/open?id=1uD...badDKWEwO2GZpT

[Digitalwave]

Bad sensor, or bad wiring, or both.

[ForcedFirebird]

The round c109 plug under the intake manifold has both the coolant temp sensor/senders and injectors all running through it. It's common for them to be corroded these days, worth looking there.

[Fraser]

The round c109 plug under the intake manifold has both the coolant temp sensor/senders and injectors all running through it. It's common for them to be corroded these days, worth looking there.

I forgot that that connector is exclusively the injectors and temp sensors- it's gotta be a problem with that. Gonna rip it apart this afternoon. Thanks for the tip!

[Fraser]

Just for the sake of closing out this thread- I got this sorted this morning. It was indeed some light corrosion that had started to corrupt the c191 connector under the intake manifold. A little cleanup and dielectric grease fixed the problem entirely. Mine didn't actually look to bad but I'll definitely keep an eye on it in the future. I should add that the screwy temp sensor readings were really messing with the whole program, all sorts of drivability and idle issues immediately went away once it was fixed. Thanks for the help!

[ForcedFirebird]

Great! Typo in my part with c109 lol. Glad you knew what I meant tho. :) I've had some come in the shop where they are running on 3cyl and the connections are completely green and chalky - with the corrosion wicking up the wires.