Trouble Code help?

RT8 · February 15, 2006

I know the GM Tech is out for a while, but I figured someone else here may can help.

1998 Z71 Silverado, 350, Auto, stock. 101K miles. Has new fuel filter, thermostat, & AC Delco platinum plugs.

I got an SES light, scan shows only 1 code: P0125. AutoZone ticket says

"The PCM has determined that the amount of time it took for the coolant temperature sensor to reach an input value consisten with closed loop operation was too excessive."

Ok, so what's that REALLY mean?

Conditions when SES light came on:

Cold and rainy. Truck had been sitting for a day or 2. Cranked and hit the interstate. Within 2 minutes of startup (~60mph) the SES light came on and stayed on for 2 days. 3rd day it was cold but very dry, light didn't come back on.

This morning it is again cool and very damp outside. Light came on again ~2 minutes into the trip and is still on.

100R1 · February 15, 2006

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

Things to check:

* faulty coolant temperature sensor

* faulty thermostat (sticking in open position)

* incorrect thermostat temperature range

Some people get this code when they put a 160 degree F. thermostat in. The engine does not get to closed loop stays in open loop and sets the SES light.

RT8 · February 15, 2006

It has a new thermostat, I put the OEM temp in it because I had already read on here about the problems with the 160.

I'm thinking its the sensor. I noticed yesterday that the temp gauge kept wandering from 180-225 or so and back pretty quickly. It was doing that before, THAT is why I changed the thermostat in the first place. It stopped...for a while.

Thanks for the input.

Anybody else?

Rookie · February 15, 2006

i would still check the t-stat. get a cheap food service thermometer put it in a pot of water and start boiling it see when it opens and chech the temp.

just my.02

Mr. Smith · February 15, 2006

Change the sensor. It is around 8 bucks or so. The sensor for the computer and not the one for the indicator. That one should be in the left cylinder head. The one you want is located under the top hose, front screwed into the lower intake. It is 2 wire with a weather pack connector on it.

RT8 · February 15, 2006

Thanks. I'll change the temp sensor (NOT the sending unit sensor) ASAP.

To reset the SES light, can't I just disconnect-reconnect the battery?

Mr. Smith · February 16, 2006

Thanks. I'll change the temp sensor (NOT the sending unit sensor) ASAP.

To reset the SES light, can't I just disconnect-reconnect the battery?

<{POST_SNAPBACK}>

That will work just fine. Good Luck

RT8 · February 16, 2006

actually, it didn't.

After changing the sensor, I unhooked the battery, reconnected and SES light still on.

Repeated several times (with both + & - terminal disconnected), no luck. Took it back to AutoZone, had 2 codes; the 125 plus a 118 (something about voltage to the sensor). I cleared them both with his scanner. They haven't come back...yet.