Coolant temperature sensor wiring

Coolant temperature sensor wiring

Postby hiker108 [OP] » October 2nd 2010, 7:01pm

I have no temperature guage reading. I removed the "dog house" and see that the wire from the coolant temperature sensor appears to be a single black wire about 12 inches long that is attached to a connector. This connector (blue) is fastened to a bracket right above the sensor. However there is nothing plugged into the other side of the connector. I appear to be missing part of the wiring harness that attaches to this connector and then to ???? at the other end. Maybe related, there are 2 connectors coming out of a harness near the a/c unit under the hood. One of these connectors is same color as
receiving connector in A/c unit. I plugged it in. The other connector is hanging in the air. Since it is colored blue, I'm wondering if this is the "other end" for the coolant temperature sensor wiring. ?????

Anyone have knowledge of the wiring for the coolant sensor??? I'm also wondering why the Haynes Maunal shows a 2-wire setup for the sensor ???

thanks
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Re: Coolant temperature sensor wiring

Postby RECox286 » October 2nd 2010, 9:43pm

Hey hiker,

There are two temperature sensors on the engine. One up front by the water outlet housing that sends info to the PCM, and the sender for the I/P gage. This sensor resides between spark plugs #3 and #5. It will be easiest to get to it from underneath the truck. Remove the connector, and assuming that the harness and circuit is intact, ground out the connection. Go turn the key to RUN, and watch the gage. If it pegs to HOT, then just replace the sender. If no joy, then it's either a problem with the circuit or gage.

Bob
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Re: Coolant temperature sensor wiring

Postby hiker108 [OP] » October 3rd 2010, 4:15pm

I removed the "dog house" inside the van and exposed the sensor that is under the spark plugs. The problem is that the wiring from this sensor
isn't connected to anything!!! A couple of years ago I had someone "fix" a problem. I think they removed part of the wiring harness.....specifically the
wiring that the pigtail from the sensor connects to. I'm not getting a gauge reading because there is no wiring to the gauge! I was hoping that someone
had some knowledge of the wiring harness that goes from the pigtail to the gauge.

thanks
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Re: Coolant temperature sensor wiring

Postby astroturf » October 3rd 2010, 4:24pm

So what you need is a wiring diagram?

When I get home I will try and find one for you unless someone else does it first.

Jim
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Re: Coolant temperature sensor wiring

Postby astroturf » October 3rd 2010, 4:55pm

This will get you started Hiker.

Hope it helps, Jim

1997 engine temp sensor wiring.pdf
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Re: Coolant temperature sensor wiring

Postby RECox286 » October 3rd 2010, 5:36pm

OK. Is there any wiring (harness) that looks close enough to make a connection? ...any wire (same color) in the vicinity that looks like it may have been cut. Keep checking the harness further up stream and see if you have a (same color) wire that goes nowhere in the bundle. With out being there to give it the eyeball, you will have to use some logic to trace this one out. If you find a wire to nowhere, With the key in RUN, try quickly shorting the wire to ground, and watch the gage. If it jumps , then you will know what you have to do.

Good luck

Bob
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Set a man on fire and he will be warm the rest of his life.

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Re: Coolant temperature sensor wiring

Postby hiker108 [OP] » October 3rd 2010, 6:14pm

I have the wiring diagrams in my Haynes astrovan book. The wiring diagram doesn't contain the details of the
physical wiring harnesses and connectors. I think I'll need to go into a chevy dealer to look at detailed parts diagram.

thanks
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Re: Coolant temperature sensor wiring

Postby Phantom » October 4th 2010, 3:03am

A harness that I was looking at has a black wire and a yellow wire for the coolant sensor , yellow is likely to be the one that connects to pcm , is there a yellow wire that has been cut in the area ?
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Re: Coolant temperature sensor wiring

Postby hiker108 [OP] » October 10th 2010, 6:16pm

The plot thickens. I was able to get a complete 1997 astro GM service manual set from ebay. It contains a great picture of the Engine Coolant Temperature sensor wiring harness.
There is a dark green wire coming out of a harness bundle near the ECT connector. The GM manual shows this green wire as being the one that I'm looking for.
It had been cut and stripped. Someone must have tried to test the gauge. It had been destructively disconnected from the ECT connector! I'm going to try bypassing the
ECT connector and connecting the green wire to the single black wire coming from the sensor. It is interesting to see that there is only a single wire coming from the sensor, while some
manuals indicate two wires coming from the sensor.
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Re: Coolant temperature sensor wiring

Postby Leeann_93 » October 11th 2010, 10:44pm

The ECT mounted on the passenger side is a one-wire sensor. The ECT mounted on the front of the engine is a 2-wire sensor. At least, it's that way on my '93 Astro and Bravada with 4.3.
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