Took my truck in last week to have my shifting issue examined. Dealer claims when they went to cold start the truck (I left it there overnight) that they didn't see the glow plug light and got a check engine light. They said the code meant that the oil temp spiked over 300 degrees (I don't have the code at the moment, and the truck sat out all night at 26 degree low so it wasn't even close to warm). They checked all of the wiring related to the glow plug and the oil sensor and tightened things up and that was that. His question to me was 'have you ever not received the glow plug light when I went to start it?' No, it is always on every single time.

Fast forward to this morning's oil change, fuel filter replacement, and tire rotation. Went to pick up the truck a couple hours later and I had the glow plug light when I turned on the key, but also the check engine light after she started. The code that time was for low coolant level. I checked and the coolant level is right where it needs to be.

Is there something going on with the wiring or the computer? They wanted the truck back in on Monday to check the wiring for damage for the oil temp spike. Now they can add the coolant level warning to the list.

Oddly, the check engine light only comes on in their parking lot. Possible there is some sort of interference coming from inside the building triggering this?

 

Sounds like your truck doesn't like that dealer and is trying to warn you with the CEL.

26 to 300 sounds like a sensor issue or maybe wiring. Throw the coolant level on top of that and I'd start looking at battery and ground connections for anything loose or corroded.

Any wrecks, alterations, modifications, bumps in the night that have happened recently?

 

Air bags and larger under bed fuel tank were the only mods over a year ago. She is garage kept and maintained regularly and on schedule... never in a wreck.

 

Somehow I don't think your oil hit 300F in a flash from 26F either.

I hope they checked to make sure you have the latest calibration.

Also, you may have a chaffed wiring harness somewhere - if the truck isn't allergic to the dealer. Odd that that it does these things just at the dealer.

One weird thing I had happen was a no start condition when I had a cheap aftermarket phone usb charger plugged in. removed it from the 12V plug on the dash and the truck fires up fine. Leave it plugged in, no start and no codes either. I wouldn't rule out interference, but yours shouldn't be the only truck having that issue in that spot.

 

A guess from the keyboard. If you can post the code.


Your truck didn't pass the EOT threshold malfunction check. 163 degrees C is around 300F. I suspect an intermittent wiring problem (possible dirty contact).
I know that one of the things the glow plugs look at to turn on is the engine coolant temperature, not sure of the EOT.




Typical Engine Oil Temperature Sensor Circuit Check Malfunction Thresholds:
Voltage < 0.10 (163 deg C) volts or voltage > 4.91 volts (-44 deg C)

 

Have a little more info from the dealer: The code was P0197... Engine Oil Temperature (EOT) Sensor Low. Dealer said that someone stood on the running board that day and the CEL went out, which led them to believe it may be a wiring issue.

From yourmechanic.com:

What the P0197 code means

This code specifically means that the resistance value the powertrain control module (PCM) sees is low in comparison to the predefined specifications. This can possibly be due to high engine oil temperature.

What causes the P0197 code?

Faulty engine oil temperature sensor
Short to ground in the EOT circuit
Faulty PCM
High engine oil temperature
What are the symptoms of the P0197 code?

The only symptom is a Check Engine Light. The EOT system is there to detect other problems with the vehicle. If the circuits of the EOT system have problems it will be unable to monitor the oil temperature.

 

50/50 guess and I was wrong. I was thinking P0198

From old memory, I think that it will start getting worse till the CEL is on all the time.


Engine Oil Temperature (EOT) Sensor Circuit Check:


DTCs


P0197 - Engine Oil Temperature Sensor Circuit Low - shorted wire
P0198 - Engine Oil Temperature Sensor Circuit High - open wire

 

Just got it back from the dealer. They found the memory code for the high oil temp stored, along with the low coolant level code. Shop manual for the low coolant level code said address other codes first, so they replaced the oil temp sensor assembly. We'll see if it recurs.

 

Hoping that fixed your issue Mark.

 

Was it a code for Low Coolant or just the "Check Coolant" that pop's up every 13,000-15,000 miles?

I suspect that was just a coincidence that message popped up at this time.
It doesn't mean you have bad or low coolant, But rather just reminder to check your coolant.

 

I wonder if there is documentation that tells if which way the thermal couples on our trucks fail. I have seen a lot of TE fail "High" when they do. But it also depends on how they are setup too.

 

The code was P2560... Engine Coolant Level Low. It wasn't.

 

Dealer resolved this by replacing the oil temp sensor. The coolant error code basically stated 'resolve other problems first.' Been all good for a few weeks now.