Been real hot here in east NC, 106 the other day while I was on the highway which is probably the hottest I've ran the truck. Im due for an oil change in about 600 miles, not sure if that would help because it's a DTC code. Turned the truck on after about an hour and a half drive north and the check engine light was on which is unusual. Got code p0197 which is the engine oil temp sensor behind the HPOP. Replaced it and also checked out the wiring, the wiring looks surprisingly good for the hot little area the wires are crammed into. Replaced the sensor and the light went away, came back, went away. Drove back home an hour and change and there was no problem. The truck starts normally, runs normally, nothing out of the ordinary which makes me want to rule out the possible PCM deficiency. The truck temp gauge on the dash reads normally, and when it reaches operating temp the check engine light will begin to go away and come back randomly. Beginning to get a bit lost in diagnosing this, anyone have this issue and any possible fixes? Of course any help is greatly appreciated.


Here's a screenshot from my forscan app, it's abnormally hot here so im not crazy about these temps.

One old forum on here a guy mentions "An EOT signal that is detected out of range high or low by the PCM will cause the PCM to ignore the EOT signal and default to a 212°F (100°C) value for engine oil temperature. The CHECK engine lamp will also be illuminated as long as the fault condition exists. A scanner tool will display a fixed PID value of 212°F (100°C) when EOT is in default.
So be light on the throttle on a cold engine since the PCM thinks it's hot and it's not". Which is what I believe im experiencing.

 

Also unplugged the EOT sensor and ran the KOEO test and got the P0198 which a guy mentions to do and pinpoints it to the wiring. Just don't want to cut the pigtail because im not sure where the wiring starts just yet.

 

A little help from the PC/ED volume of the Ford Service Manual is attached.

 

Did you ohm out the old sensor verses the new one?

One common problem is with the EOT sensor wiring or wiring connector. A short to ground (frayed wires) or loose wires at the connector in the EOT circuit will cause an intermittent CEL to show up. It’ll also cause poor starting and running behavior as well.

 

I did not, when I took the old one out some oil began to leak and it fell right into it before I could get the new one in. It's parked and I'll have to get in there and check the electrical tomorrow. Thinking about just ordering a pigtail

 

Wow this pdf is great, where'd you get this? thank you btw

 

For anyone who may stumble upon this thread, I ended up finding it with the help of that attached PDF from sous.

- The pdf is a great place to start if you've changed the EOT sensor & pigtail with no success.
- Check the continuity of the pigtail before you start to get flustered. Ohm it out, if you're below 5ish ohms like I was there's probably a short to ground or fray in the wire (mine was a fray).

EOT pigtail and what values you will be measuring when you are checking the continuity of the pigtail.

Mine was a small fray


Here is the wire that was frayed, same wire that goes to your EOT travels to the 42pin connector.

Don't mind my splice job, if you're reading this go fix YOUR truck because mine is running threw some electrical tape on it and we were good to go.

Here's some other PDFs I found online in regards to the EOT, and other sensors alike.