2007 4.6L V8 Oil Temperature Sensor

[Diesel Tom]

My son started home this morning from work. He didn't hold the starter long enough on the first try, so he held it longer the second time. The car started OK, but the Check Engine Light immediately came on with code P0197. That code is for Oil Temp Sensor voltage low. Oil temp. sensor, what oil temp. sensor? Only big trucks with Diesel engines have oil temp. sensors, right? Wrong, his engine has one!

After some research (mainly with the Ford Manuals), I found the following out:

1. There is no coolant temp sensor for the engine control unit. (The 4.0L V6 engine has a conventional coolant temp sensor)
2. There is one (not two) cylinder head temp sensor.
3. There is an oil temperature sensor located in side of the oil pan. (very easy to get to, but very vulnerable to debris from the road hitting it)
4. No major parts supplier lists the oil temp sensor. (which looks very similar to a coolant temp sensor)
5. My son reported that the engine temp gauge behaved normally on his 60 mile trip home this morning.

I squirmed under the car and wiggled the connector on the oil temp sensor and it appeared OK. I am assuming (always dangerous) that the oil temp sensor controls the engine temperature gauge on the dash and that normal operation of the engine temp gauge says the oil temp sensor is OK. I reset the CEL.

Any thoughts?

Has anyone had to replace one of the oil temperature sensors and where did you get the replacement part?

 

[MNgopher]

The oil temp sensor has nothing to do with the coolant temp sensor or the temperature guage on the dash. The oil temp sensor is used as input into the Variable Cam Timing (VCT) as oil at different temps has different viscosity and affects the operation of the VCT timing. It can also be used in determining the engine is too hot and start initiating disabling of engine cylinders to help bring temps down. F150's with the 5.4 3V engine had this same sensor. Later versions did away with this sensor, but ti was used on earlier units.

The Engine Coolant temp is not directly read in these engines but is inferred through an algorithim using the Cylinder Head Temp Sensor (and yes, there is only one on these engines). The data from the CHT is sent to the powertrain control module and what you see on your guage is what is computed to the be the engine coolant temp.

Can't tell you what the part number is directly.

 

[David Layton]

I have an 06 Explorer V8 and my fan runs continually. I'm wondering if one of these sensors is sending false readings? My engine is not overheating to cause the fan to come on. It comes on as soon as I start the vehicle.

 

[Diesel Tom]

The particular temp sensor described above is not connected to the cooling fans. MNgopher is correct. The sensor is connected through the Engine Control Unit to the Variable Valve Timing (VVT) solenoid which affects the valve timing.

David, Is the fan you are talking about BEHIND the radiator (instead of in front of it)? The fan behind the radiator is driven by the serpentine belt and will operate whenever the engine is running.

 

[David Layton]

When this comes on....and you take off, it sounds as if your engine is revving up way to high.....its definitely a fan. The other fan runs quiet.

 

[gdgiordano]

The particular temp sensor described above is not connected to the cooling fans. MNgopher is correct. The sensor is connected through the Engine Control Unit to the Variable Valve Timing (VVT) solenoid which affects the valve timing.

David, Is the fan you are talking about BEHIND the radiator (instead of in front of it)? The fan behind the radiator is driven by the serpentine belt and will operate whenever the engine is running.

The fan behind the radiator has a clutch on it that should engage and not depending on temp.

 

[David Layton]

Yes. This engages at random times.It's very loud. It engages and sometimes will run for 20 min. Sometimes only a few minutes. I'm not losing any coolant nor does my temperature gauge ever show signs of overheating. Im just not sure why this fan engages so often, and it's just been in the past few weeks.....

 

[Diesel Tom]

The fan on this model is different from fans in the past. In the past, there was a thermostatic element located in the fan hub which reacted solely to the temperature of the air around the fan. When it got hot, the clutch engaged the fan. When it got cooler, the fan freewheeled. On this model however, the fan is controlled by the Engine Control Unit and reacts to a number of different inputs: 1) coolant temperature, 2) air conditioner compressor pressures and who knows what else. Yes, you can hear this fan engage and the roar gets louder periodically. If your temp gauge is sitting steady and not rising, the fan is doing its job properly. I know the climate in MN is cooler than it is where I live in GA, but could you have been using your AC more in the last few weeks? That alone could explain why the fan is coming on more often and longer.

By the way, back to my original message in this thread. My problem turned out NOT to be the sensor. The cable going to the sensor had rubbed away the insulation on one of the wires and was shorting to ground. Reducing the stress on the cable and wrapping the wire with electrical tape cured the problem.

 

[Reacher70]

I know everyone is kind of going in a different direction with the answers here so I'm going to focus on something else, In your first sentence you said he didn't hold the start position long enough and it didn't start, then he did the second time and it ran fine. I know on mine when I do that it will usually throw me some kind of weird code. What I think happens is the PCM thinks the motor started but then sees no reading from sensors that should be sending information. I have just cleared the codes and haven't noticed anything in drivability or otherwise.

It kind of sounds to me like this is what happened. I would just clear the code and see if that code comes back after normal driving and starting.

 

[Diesel Tom]

Reacher 70, please read the last sentence of my reply just above your reply. The problem was due to frayed insulation against a sharp metal edge. Although the problem first showed up when my son didn't start his Explorer properly, it was purely coincidental. I could clear the code and it would come back, usually within the day. When the frayed insulation allowed the wire to contact the metal frame, the code was set. Repairing the frayed insulation solved the problem permanently.

 

[David Layton]

I am in Virginia, humidity central. With your explanation making 100% sense, why would this fan start as soon as I start the vehicle for the first time in the morning and run for 15-20 min?
I purchased a coolant temperaure sensor and will be replacing to see if I get any results. Cheap part, not so hard to do.
I wouldn't be questioning this if it had not just started being so noticeable after owning the vehicle for 12 years.
I will keep you gents updated. Diesel, didnt mean to hikack your thread!

 

[Mart1n]

Hi David, sounds like I have the same issue as you. did you get to fix it?

 

[David Layton]

Hi David, sounds like I have the same issue as you. did you get to fix it?

Sorry, I haven't updated until now.
This is crazy. I forgot to mention that I put new plugs and ordered and installed aftermarket coil packs on my explorer as well.
After a week of this fan running, I put the old coil packs back on. Fan has not turned on since. I talked to a ford mechanic and he said that aftermarket coil packs can cause different issues. Took it a step further. Installed the same coil packs and my parents explorer, same result, fan ran continuously. Changed back, no problem.
Anyone recently changed their coil packs??

 

[Mart1n]

This is great info! I bought the truck early this summer, and I know the coil packs are aftermarket (yellow and not Motorcraft).

1998Explorer gave me a pinpoint procedure to troubleshoot my fan issue, but if it fails, I'll certainly look into changing the coils back to Motorcraft. I'm also interested in hearing from community. But with the double test you conducted I think you found it in your case anyway.

 

[Explorer_PL]

I can tell you from an 11 year experience with my v8, the ignition system on the Triton motors does not like non-OEM parts. I installed Accell yellow coils, and it almost cost me a transmission replacement since they went bad quickly, and were affecting the TCM harness. The dealer diagnosed it to be a bad TCM/valve body assembly (mechatronic) and recommended a total replacement since the car had already 200k. I kept digging on the internet I found out that the coils cause that condition. I never checked them since I just installed them so assumed they are good - wrong. Use Motorcraft only - that's my motto now.
After I installed OEM coils, all is good at 268k.

 

[Mart1n]

This is really informative... I've been looking up the Motorcraft coils, there seems to be more than one part number that fits?

 

[Mart1n]

looking at the price difference multiplied by 8, I see why the previous owner put aftermarket coils vs Motorcraft

 

[Explorer_PL]

Yes, they are expensive.
Look for deals on eBay or Amazon.
The best I ever got was about 350 for 8 of them.
At a dealer, one costs $ 80

Makes you wonder the quality of sets online where you can get all 8 for $ 99.99

 

[David Layton]

looking at the price difference multiplied by 8, I see why the previous owner put aftermarket coils vs Motorcraft

2 years later and I have not had the fan issue since....it was definitely the aftermarket *cheap* coil packs.
Unbelievable. I still don't understand how the 2 were connected, but after personally doing this on identical vehicles and having the same result, I am 100% concinced.
I hope this helped you guys out!!

 

[Diesel Tom]

I'm not at all surprised that third-party coils caused a problem. Modern cars are seething with unwanted RF signals which wrack havoc with sensitive circuits. One big reason is that Detroit is too cheap to use shielded cables for the very sensitive circuits. Oftentimes, electrically noisy circuits run in the very same wiring bundle as the sensitive circuits.

The third-party coils probably have a "noisy" switching circuit which injects a noise spike every time a cylinder fires.