I just bought a 98 blazer 2wd with 4.3l v6. The temp sensor for the gauge which is in the side of the drivers head has it's wire running up on top of motor and plug is attached to bracket. But there is no wire coming from the harness to the plug.

I have searched all over for this missing wire. I have even looked in the harness loom in-case it was cut or broke. But I can't find it.

Can someone tell me where the wire comes out of the main harness? Is the wire black in color?

Anyone have an engine wire diagram?

 

How many wires does the sensor have going to it? '98 was the first year for the single, two-wire sensor which was used by both the PCM & the instrument cluster. The ECT sensor was located in the lower intake manifold near the t-stat housing which was the same location from '96 through sometime in '98 or '99. After that it was moved to the driver side cylinder head where the older '96-'97 engines had a 1-wire temperature sending unit.

Could you take a picture of the noted area and post it?

 

The sensor in the head has 1 wire. There is the sensor on the front that has 2 wires.

Do you think they but the sensor in the motor but never used it?


My main issue is the temp gauge doesn't work, which is when I found the sensor in the head had no wire going to it's plug.

Other gauges are not working either.

 

What else isn't working? Have you tried to see if the PCM is getting the proper temp data?

 

First, thank you for helping, I see you answer a lot of questions here. Thank You.

Here is the whole story:
I just bought the blazer and the temp, oil, fuel gauges do not work. The volt, rpm, mph do work. Dash lights do not work.

Driving to work the first time(no a/c on) ran great no issues. Coming home it was close to 100 degrees outside and had a/c on, about 30 minutes into the trip the motor lost power, would not rev and died. I put it in neutral and coast a minute then restarted it.

It started back up drove 2 miles and did it again. Was close to home so restarted and drove fine. Did it one last time.

Pulled it in garage. Without temp gauge I could not see if it was overheating. Thats when I noticed the temp sensor in drivers head not plugged in. Guess they put one in it but not used for 98 model year.

The motor did feel hot, but I am not a thermometer. When I pulled the oil dipstick the metal stick was to hot to touch. So may be overheating.

I got stuck on finding the missing plug for the temp sensor and have not drove it but a short trip and it ran fine.

Tonight(after work) I will ground the sensor wire and see if the gauge moves. If so I will get a new sensor. If not I am thinking it might be the gauge cluster.

If it is the cluster, I have read here they have bad solder joints. I can fix that so will try that first.

Any thoughts on why it died and started back up fine? Usualy if they die from heat(if you don't damage motor) they run bad right after till cooled down.

 

Have you checked the GAUGES fuse in the instrument panel fuse box?

 

Yes. When I pull the fuse the gauges do drop to low. With fuse on and turn the key gauges rise a bit. Gas gauge goes to half and stays there the whole time.

Might be sending unit on gas gauge, will have to check resistance on it.

 

Turned out to be temp sensor on front of motor. Weird that it has the unused sensor in head. Thanks for the help.

 

Glad to help!