For a while I havent been able to get my fans to run normal. Originally I started off with replacing the thermostat, coolant temp sensor, and fan switch. Still couldn't get anything. I now purchased an aftermarket relay kit with its own sensor.

I removed the factory coolant temp sensor and replaced it with the temp sensor from the aftermarket kit. Would this cause the check engine light to come on? If so, is there a fix?

Yes it will.

The ECU uses the coolant temp sensor to regulate the AFR among other things.

IIRC, no CTS will make your car run pig rich.

There is not a fix for this, put it back!

You could tap a hole for your external sensor in the therm housing if you wanted to.

Where would you recommend tapping this. It's the same size and thread as the coolant temp sensor.

Here is a picture of the aftermarket sensor I need to tap on the left



Here is thermostat picture to reference.



Thanks for the help.

Mine is tapped in the left hand side flat spot for my GM cts. It's thin, but it's thick enough to get about four threads cut in, and it seals fine.

This says it can be tapped into the engine block or intake manifold also, what would be the best recommendation as for ease of the install, also its 3/8" thread.

side of thermostat housing

Originally posted by zwickyj
also its 3/8" thread.

You mean 3/8" NPT? That is a different than 3/8".

3/8"-18NPT

Originally posted by zwickyj
This says it can be tapped into the engine block or intake manifold also, what would be the best recommendation as for ease of the install, also its 3/8" thread.

You're not going to find a spot on the block, and our intake manifolds don't have coolant passing through them.

Thermostat housing is the place to go.

Scroll down a bit to the Coolant sensor heading. That will show you where/how;

http://www.2gnt.com/index.php?d=MSnS_INSTALL_(parts/wiring_only!)

That's perfect, I was actually thinking about teeing of the fitting for both originally, but I might as well just tap that and my compressor housing while I'm at it. Thanks everyone.