Background: 2010 Ranger 4.0L V6, VSS wire is tapped to the VT/OG wire on Pin #1 the center PCM plug on the firewall inside the engine bay.

Problem: The temperature is reading 5-8 degrees high. Furthermore, it is constantly fluctuating every several hundred yards by a degree or two. For example, the temperature outside might be 84F, but it will read 85, 86, 87, 90, 91, 87, 88, 89, 88, 89, 92, 89, 88, 89, etc. etc.

In terms of the temperature sensor, it is the correct one with the BU/WH, BU/YE wires. I originally mounted the temp sensor just inside the grill on the flat area just in front of the radiator but behind the decorative grill (as I did on my 2002 and other early 2000 Rangers). After just reading really high, I opted to relocate the temperature sensor so that is is ziptied directly to the decorative grill to ensure constant exposure to airflow (and minimize the image of heat from the engine).

I have gone through the old threads on this issue and what I am thinking is that either the tap to the VSS wire is not secure enough (although it is connected and seems secure from what I can tell), the temperature sensor itself is just bad and needs to be replaced, or the OHC computer is wacky. I could shift the VSS tap to the cruise control rather than the PCM module but I doubt this will solve the issue. All help/guidance greatly appreciated!

 

VSS = Vehicle speed sensor

Temp sensor??

Not sure of the connection between these?

Is this a temp sensor for a display on the dash or Overhead?

 

OHC = (Explorer) Overhead Console. The console displays temperature (via a sensor) and has a compass, map lights, and makes a man's truck totally awesome :D

 

I would use 2 pins(sewing needles) to pierce the sensor wires, measure voltage, see if voltage is changing with no temp change, also heat up sensor(match or lighter) BRIEFLY, to see voltage response.
Then unplug the sensor, or cut the wires, and measure voltage from the OHC, this should tell you where the temp fluctuation is coming from, sensor or OHC.
You can also test the OHMs on the sensor, see if it stays static with no temp change, which it should.

Generally temp sensors are resistance sensors, higher temp = higher resistance.
If the sensor wires are run near a heat source that can effect resistance, it shouldn't but it can.
If you disconnect the sensor wire at the OHC and then test OHMs thru sensor while engine is running and they change then you either have a bad sensor or wire to sensor.

 

hey pastfinder
did you find your temperature sensor problem.
i try to install mine on my ranger 2008. can you tell me exactly where you tap the vss wire. i read a lot but only found some stuff for 2004 and older.
picture will be apreciate or juste your wiring diagram
thank a lot.