Two trucks that run like crap! Coolant temp sensor problem.

[Mike Robinson]

I'm baffled. I'm having the same problem with two of my trucks, 94 K1500 and 93 C1500 both 5.7/4L60. The service engine light would come on occasionally showing a code 15. They were both running fine. So I replaced the temp sensor (next to the thermostat) and now they both run like crap. They both barely run and are running very rich. I didn't touch anything else. Simply unscrewed the old sensor and screwed in the new one. Thanks in advance for any info!

 

[skylark]

There is a ground located on the stud for the thermostat housing, it is possible that you disturbed it but more likely if you got the sensorsfrom the same place you could have a couple of bad ones. Throw the old ones back in and see if it runs like it used to.

 

[Justin S]

if both were changed and both run bad, sounds like you were sold the wrong sensors?

 

[Mike Robinson]

They were changed at two different times. I had this problem with the 93 a few months ago but I haven't had time to mess with it yet because it's being painted. The service engine light has been coming on occasionally in this 94 so I figured I'd fix it today. Now it is acting exactly the same as the other truck. The grounds at the thermostat are good. I reinstalled the old sensor and disconnectedthe battery. Still runs like crap. It'll barely start unless you give it throttle and even then it'll barely run.

 

[Justin S]

so it ran fine until you changed the sensor, and didn't change back when you put the old one back?

 

[Mike Robinson]

Exactly. I'm starting to think it's a bad connector. The wires are extremely short and bent at a 90 from the factory. It's like that on both trucks. I bet there's a break in there somewhere.

 

[Dylan1991_1500]

I have seen the terminals inside the connector get really green with corrosion. That would cause reading errors that could tweak out the ECM. That's why they sell replacement pigtails to go with those new sensors. Just don't try to install an ECM sensor where the gauge sensor goes.

 

[Mike Robinson]

Well it looks like Dylan is the winner. It was a bad connection inside the connector itself.

 

[Justin S]

Dylan's only had a Chevy for a few months and is already an expert. Is that the case on both trucks?

 

[Dylan1991_1500]

That's is why you hire me...I am expert.