Had a horrible realization yesterday... When I bought my car it overheated so I corrected the problem by grounding out the temp sending unit's wire to the frame. I then installed a mechanical guage and cut the wire to the sensor that fed the guage in the dash cluster.

From the computer's point of view, how bad was this? From what I have been reading it seems that this was a huge blunder on my part. Am I correct?? Did the computer not seeing the coolant temp adversely effect my cars performance?

 

The ecm doesn't use the same sender as the guage.

 

Right, but does the other one in the passenger side cyl. head send any signal to the ECM? That one is the temp sending unit correct? Or is that simply a fan switch? I never had any SES lights or codes so...

 

It's only a fan switch that grounds the wire to the block when it reaches a certain temp. The wire is the ground wire for the pass. side fan relay, so I intercepted that wire and ran a new wire to the dash where I have a manual fan switch. The ECM doesn't know or care when that fan is on/off, at least in the MAF cars...

 

Other than the fan temp switch, is there more than one temp sending unit? Thought there was only one. Not counting the cold start switch and the MAT. Although, I had intermittent failure on my dash display while the ECM was still reading fine...

 

ECM Temp Sensor is in the front of your intake next to the Cold Start Switch (if you have one), also next to the manifold coolant port.