ECT sensors

[Dennis Wilkie]

Can anyone tell me why I would have 2 ECT sensors on my 1992 k1500? I never really paid that much attention until today when I noticed it was taking forever for the truck to warm up, but it dawned on me that there is 1 on the intake with the 2 prong pigtail, and 1 single wire sensor between the 1 and 3 cylinders. The one between the cylinders directly impacted my gauge reading awhile back. I had to clip the wire and put another terminal on it and it worked perfect for a couple months. But now it's not reading above 125° no matter how long it's been running or driven. I replaced the one on the intake awhile back when I replaced the thermostat and radiator, so I know its good, but I don't know what to think about the side sensor now. I'm going to replace the thermostat again tomorrow just to be on the safe side since it's acting like it's stuck closed.

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[df2x4]

If I recall correctly the one between the cylinders feeds a signal to the gauge cluster and the one on the intake feeds a signal to the PCM.

 

[PlayingWithTBI]

If I recall correctly the one between the cylinders feeds a signal to the gauge cluster and the one on the intake feeds a signal to the PCM.

^^^ That's right and they were called CTS (Coolant Temp Sensors) during those years (87-95) FYI.

 

[Dennis Wilkie]

Is the cylinder side sensor known for going out often? Because for some reason i'm getting a weak signal to my gauge after I replaced my intake and head gaskets.

 

[Gramps]

No they are generally pretty reliable. Make sure your ground wires have clean tight connections. (Back off pass cyl head to firewall, block to frame rail, battery neg to frame rail)
That sensor “self grounds” but if your block grounds are poor it can cause the sensor to act up - amungst other issues.

 

[Dennis Wilkie]

If it is a ground problem, I'm pretty sure I know exactly which one it is. Because there are only 2 that I had to mess with, and I thought I might have pinched one by the thermostat housing. I'll look into it in the morning

 

[Schurkey]

The sensor in the head needs to be installed with chemical sealant, NOT THREAD TAPE.

Or use no sealant at all. (I'm not brave enough for that.)

The sensor grounds via the threads, if you put too much sealant on them, you get poor grounding of the sensor.



Test the gauge by pulling the wire off the sensor, and ground the wire. Gauge should peg. Let the wire hang in the air--gauge should peg the other way.

 

[Dennis Wilkie]

I've never touched the sensor other than to connect that clip on it. The wire was barely together so I had to snip it and put another terminal on it. It's on there nic and snug, but maybe it's still the terminal itself. I don't know...i'll just redo that whole section of wiring again tomorrow. That's the only way to be sure