What is the sensor just to the left of thermostat housing. There are two sensors, and I know the one to the right of the thermostat housing is the temperature sensor. Need to know the one to the left.

 

What year is your truck. For many before 1998, there was actually 2 temp sensors. One was to send the signal to the gauge cluster, and the other to the PCM. In later years, those two functions where combined into one sensor.

 

1997 Ram

 

Ya, then you more then likely have the two sensor set-up. If you are replacing them, you will need to replace them both so that they talk to the PCM and your cluster correctly.

 

Is that sensor also a temperature sensor? I already bought one to replace the one on the right of the themostat housing. The one on the left only has one metal prong, whereas the other one has two

 

Ya, one is just basically a sending unit, and the other is a sensor. When you ask for the parts at the dealership or parts store, tell them you need the two different ones.

 

Will do, thanks. Hopefully, they have got it.

 

To clarify a little more, typically the one to the left of the thermostat housing is the coolant temp sending unit that provides data to the temp gauge and dash warning light. The port just behind and to the right of the t-stat housing is the sensor for the PCM (also called the ECT sensor).

 

Single wire sensor is for the gauge, the two wire sensor is for the PCM. You do not need to replace both, only whichever one is bad, they are not linked together in any way. The one for the PCM will affect how the truck runs, the one for the gauge just tells you what temp it is running.

 

I think he is replacing them as part of his plenum work.