1999 F150 temp gauge is running to H and my check engine light is coming on. I'm getting a code p1299 -- (Cylinder Head Over Temperature Protection Active). However the engine is not overheating. So I replaced the coolant temp sensor and I'm still having the same problems. Any suggestions.

thanks

bp
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How do you know the engine is "cool". Does it happen immediately upon startup? Have you installed another form of temp monitoring? Just asking, because if you replaced the sensor, I'm not sure what else tells the computer the temp reading. How long does the truck take to get to "H" on the gauge? Need more info please.

 

It usually happens after about 10 to 15 mins of driving. The gauge reads normal operating range for about 10 to 15 mins then jumps to H and the overheat light also comes on. The engine has been checked with a laser temp sensor while at a friends shop. The engine was cool the radiator was cool and not steaming. cool(normal ranage).


thanks
bp

 

I suppose the gauge itself could be bad. Does it jump quickly like a tachometer, or just rise quickly but steadily to the "H"? You can buy a manual temp gauge that will install on your truck for about $30. Does the 99 model have the digital odometer? If so, you can follow the sticky at the top of the forum that gives info on how to use the digital odometer as among other things, a temp gauge, and a tach. I would be interested to know what that reads.

 

My former F150/4.2 (2000) did this a few times after having the lower intake manifold gasket replaced.
I never knew exactly what caused it. Since I sold the truck months ago, I do not know the outcome (if any).
Here's what I experienced:
It occured maybe 5 times.
The temp gauge would suddenly shoot up to H.
The check engine light would come on.
After this occured a few times, I figured out all I had to do was turn of the engine, restart it, and all was normal.
Actually, one time I did this while driving down the hiway. I put it in neutral, turned the key off, pushed in the clutch and immediately restarted the engine. Everything went to normal. Go figure???
I never saw any ill effects from this strange "overheating" / "check engine" situation. The truck always ran fine.
On several occasions I'd pull over and jump out to check for overheating symptoms. Removed the degas cap and everything appeared normal.
(I know - you should never open the cap on a hot engine, but I did anyways. Don't tell my mom.)
I kinda' dismissed it as maybe being related to something that got messed up in the wiring harness during the gasket replacement.
If that wasn't the cause, I don't know what was.
I thought maybe an airpocket in the coolant system but that never seemed to make any sense. The coolant was circulating fine and I seem to remember I even drained much of the coolant and carefully refilled so as to try and eliminate any airpocket.
I finally decided I was just going to drive it regardless and if it blew up, I'd then know what was wrong and fix it.

Someone mentioned a head gasket going bad, but I never knew what - if anything - happened to it.

please let us know if you get it figured out.

 

When it goes to H it jumps quickly. I know the truck is not over heating so if it was a bad guage I wouldn't mind so much but the truck goes into limp mode (over heat protection mode) and fires on ever other cylinder when this happens. Can't drive to far that way.

thanks

bp

 

hmmm, mine never did that. It does indeed appear your truck's ECM believes the truck is overheating, and taking the prescribed action.
If it is for SURE not overheating, then I'm left scratching my head. It appears it is time for some serious get-out-the-book troubleshooting.

 

Problem finally solved. Of all things it was the thermostat, although it never showed any of the tell tell signs of a bad thermostat. Thanks for all your suggestions.

Bryant

 

I have had the same problem with the temp gauge hitting Hot. Likewise, I put the truck in neutral, turn it off, turn it back on, and the gauge goes back to normal. I have replaced the CHT sensor, replaced the thermostat twice and i am still having the same problem.

Any suggestions? Just about at my wits end trying to find a solution.

 

Hey j, welcome to FTE!

Not sure I can offer advice that will lead you directly to the cause, but will ask: What model year and how many miles.

I'd consider the radiator as a possible culprit.

My 2000 model started having goofy overheating issues at about 130,000 miles. I had the radiator rodded out and problem solved.

worth looking into maybe?

Good luck with it - keep us posted.

 

Bryan,

Its a 1997, F150, 5.4L, and has 216,000 miles.

I burped the radiator this past weekend. It has been 4 days and I haven't had the problem reoccur, so I am keeping my fingers crossed.

Thanks

 

Yes, there have been a few cases where guys had air pockets trapped in the coolant passage.
Once cleared, the problem never came back.
Hope this is true for you.