Does anybody know exactly what what sensor is involved with a PO125 OBD II code? It is a temperature sensor warmup fault. I was told to replace temperature switch PRC 3505. What is this switching

Any thoughts would be appreciated!!

Cheers,

 

that is the coolant temperature sensor. try checking your coolant level before you have the sensor changed. low coolant levels can trigger this code.

 

What year and model are you driving??

 

Sorry, I should know better - its a 96 with the 4.0L V8 with about 220K on it

Cheers

 

Is your truck warming up? If your thermostat is stuck open, your truck will not get up to operating temp, if your coolant level is not right or you have air, it will cause this problem, and if your switch is faulty, it will cause this problem.

 

Truck warms up fine, stays in normal operation range on the dash gauge. Only reason I know about it is from the OBD codes. The Sender to the panel gauge is a different unit. I don't know if the acutal unit is a sender or a switch. Its refered to as both in different documentation.

Secondly, where the ?#@$%@ is it?

The parts guide shows it either on the theromstat housing on early models and a vague indication of it being on the upper right side of the engine on the later models. I'm starting to think it buried under the intake manifold .....

Cheers,

 

OKDisco-
Is that true? I was always under the impression that the thermostats main purpose was to help the engine warm-up quicker and once the threshold was reached, it would open and allow coolant to flow throught the system....especially helpful in the winter months.

I would guess that if a thermostat was stuck open that the truck would warm up to operating temperatures, it would just take longer to do so...right? Maybe I missed this class in autoshop.

 

The temp switch should be right next to the sending unit on your intake manifold. Right by the thermostat housing. I would go with the switch (1 wire) . If it was your sending unit, you would get a P0116.

 

Unstable- if the t-stat is open, it takes longer to warm up the engine, thus keeping it outside of the threshold to go to full closed loop. In the winter, your vehicle will never reach operating temp on the highway. This is possible in warmer weather as well, but it will get up there when at a stop. It will not maintain a constant operating temp, thus kicking the fault and killing your valvetrain over time.