99 2.7 p0125

So my 316k mile truck just through a p0125 code Insufficient Coolant Temperature for closed loop control.

Now first thing I came across was the ECT Sensor..but after looking over the threads it seems the 1st gens usually get a bad 02 sensor.

The truck has a long tube header on it as well, maybe the 02 is just fried. Seems like a simple bolt in and out sensor.

I'm thinking replace the front air/fuel sensor first...reason is it seems the gas mileage is kinda bad for this 4 banger.

 

If it’s a coolant temp problem, the AF sensor shouldn’t have anything to do with it. I wouldn’t throw parts at things unrelated to the code.

there should be two coolant temp sensors. One for the gauge and one for the computer. Test/replace the one for the computer.