[TheKrieg]

Hello i need some help. I just put new spark plugs and new wires on my truck. It's a 2003 sonoma with the 4.3. It starts up but it's very rough at idle and the check engine light came on and instead of me thinking its a misfire, it's a p0118(engine coolant tempature sensor circuit high voltage which wasn't there before please help asap, thank you.

 

[hogster]

Hello i need some help. I just put new spark plugs and new wires on my truck. It's a 2003 sonoma with the 4.3. It starts up but it's very rough at idle and the check engine light came on and instead of me thinking its a misfire, it's a p0118(engine coolant temperature sensor circuit high voltage which wasn't there before please help asap, thank you.

the "rough idle" and the coolant sensor warning are probably separate issues.....Possibly could have disturbed the elec conn/wiring for the temp sensor during driver's side plug changes-check & confirm all a-ok...see this vid for its location: chevy 4.3 coolant temperature sensor location - Bing video ....as far as the "rough idle"?.... may be due to a "barely/parially" engaged plug wire, either @ the plug, or @ the Dist. cap.. I had a BEAR of a time getting a good sealed conn @ the Dist cap when I changed plug wires.

 

[oldeerslayer]

You have a faulty ECT sensor or the wiring has a problem like a corroded connector or it's unplugged. It's at the front of the intake manifold and will have a black and yellow wire connected to it.
You should not have come anywhere near it changing plugs or wires, but I wasn't there. Maybe you set your tool box on it.
Probably just a coincidence. Not good for your motor to drive w/o it because the engine will run extremely rich. If it clogs your catalytic converter the cost to replace that will be astronomical on an 03 4.3L.
That likely explains your rough idle. If the PCM thinks it's -40° the fueling will be way too rich.
Which can foul spark plugs, among other things.
They are easy to replace, but if you need help unplugging the connector or unscrewing the sensor there are plenty of Youtube vids. Just be sure it is for the correct location as Chevy moved that sensor around a lot over the 4.3's 30+ year production run and most on You tube vids are the wrong one, for the gauge sender in the cylinder head of older 4.3's. Like the video linked above. It is not for your truck. You also don't need to drain the cooling system. These engines can be a bit difficult to get all the air out of if you do that. Almost nothing will come out during the 2 seconds you have old ECT sensor out and the new one going in. Trick is to leave the radiator cap on so the system is air tight.
Finding the video for correct year is the trick. In the 40 years that I have been working on S-10s the most important thing I've learned is that no 2 are the same.

 

[hogster]

You have a faulty ECT sensor or the wiring has a problem like a corroded connector or it's unplugged. It's at the front of
the intake manifold and will have a black and yellow wire connected to it.
You should not have come anywhere near it changing plugs or wires, but I wasn't there. Maybe you set your tool box on it.
Probably just a coincidence. Not good for your motor to drive w/o it because the engine will run extremely rich. If it clogs your catalytic converter the cost to replace that will be astronomical on an 03 4.3L. They are easy to replace, but if you need help unplugging the connector or unscrewing the sensor there are plenty of Youtube vids. Just be sure it is for the correct location as Chevy moved that sensor around a lot over the 4.3's 30+ year production run and most on You tube vids are the wrong one, for the gauge sender in the cylinder head of older 4.3's
Some You tube vids are very helpful, some not so much. Finding the correct year is the trick.
View attachment 367560

wow, Deer..guess so!..the pic u posted shows stuff, like the air snorkle and filter box, located completely diff than my 2000 V6 S10..what yr/model S10 was this pic from?

 

[oldeerslayer]

Oh, crap. My bad. That's a pic of a Silverado or Tahoe. The 5.0, 5.7, and 4.3 all have the same CTS location and that's what I was looking at when searching Google pics that showed it's location. Didn't even look at the back of the engine.
Important part is it does show where the late Vortec ECT sensor is located. They are no longer in the side of the cylinder head by 03.
Some years had 2 the ECT sensor in the intake and the gauge sender in the head.
IIRC it was in 2001, when the GM started using the 0411 computer on all the trucks, that they realized having a separate analog sender, wiring and gauge was redundant since they already had serial data going from the PCM to the gauge cluster and that by making the temp gauge digital they could eliminate the other stuff. Which would save them money.

 

[Hoosier Rick]

Coolant sensor should be in driver side cylinder head. Make sure sensor is not broken or connector unhooked.

 

[TheKrieg]

You have a faulty ECT sensor or the wiring has a problem like a corroded connector or it's unplugged. It's at the front of the intake manifold and will have a black and yellow wire connected to it.
You should not have come anywhere near it changing plugs or wires, but I wasn't there. Maybe you set your tool box on it.
Probably just a coincidence. Not good for your motor to drive w/o it because the engine will run extremely rich. If it clogs your catalytic converter the cost to replace that will be astronomical on an 03 4.3L.
That likely explains your rough idle. If the PCM thinks it's -40° the fueling will be way too rich.
Which can foul spark plugs, among other things.
They are easy to replace, but if you need help unplugging the connector or unscrewing the sensor there are plenty of Youtube vids. Just be sure it is for the correct location as Chevy moved that sensor around a lot over the 4.3's 30+ year production run and most on You tube vids are the wrong one, for the gauge sender in the cylinder head of older 4.3's. Like the video linked above. It is not for your truck. You also don't need to drain the cooling system. These engines can be a bit difficult to get all the air out of if you do that. Almost nothing will come out during the 2 seconds you have old ECT sensor out and the new one going in. Trick is to leave the radiator cap on so the system is air tight.
Finding the video for correct year is the trick. In the 40 years that I have been working on S-10s the most important thing I've learned is that no 2 are the same.


View attachment 367560

Thank yall very much yea the connection wasnt plugged in all the way and i got tricked with tempature sensor because i did sparkplugs and thought it was a misfire still getting used to thia and learning from my mistakes fixed it though and running much better now didnt run it more than 2 minutes like that so no damage was done luckily.Thank you.Have a good day

 

[Hoosier Rick]

Thank yall very much yea the connection wasnt plugged in all the way and i got tricked with tempature sensor because i did sparkplugs and thought it was a misfire still getting used to thia and learning from my mistakes fixed it though and running much better now didnt run it more than 2 minutes like that so no damage was done luckily.Thank you.Have a good day

They run terrible if the sensor gets unplugged. The lock was broken on my Jimmy. One day the wire came off about halfway to work. Had to stop and plug it back on.