I own a 2000 Ford F-250 5.4 Automatic.
It towes my 5th wheel trailer very good.
On our last trip it suddenly experienced the "check engine light" effect.
The light turnes on ramdomly and either goes of after a couple of seconds or it doesn't go on when I restart the engine.
It is mainy anoing, but when in towing it really hurts, because the engine switches into an emergency mode and stalls.
I read that the engine uses only 4 cylinders.
I read many arcticles on the web about that light, but I couldn't find a solution.
The thing is I brought the car to several repair shops but none read a code from the computer.
I think it's not a real fault but a misreading or mabye a cable thats grounding?
The problem is, I can't bring the car to a repair shop, because there is nothing wrong with the car.
So that's my question for you really experienced guys: how can I find the source of the problem?

 

Go to a shop or auto parts store and have the code read. If it has came on multiple times it should have left a fault code. With that you can plan your course of action.

 

That's the problem: I have tried to get a code read, but there is none!
I even bought a ODB reader and it also reads no codes.
So what can it be to, that something is wrong, but no code showes up?

 

If your engine is going into limp mode, then there is an error code being stored.

 

Again: there is no code stored. I was with 3 repair shops and used my on ODB Reader, no code!

 

There has to be more to the story that you aren't telling us.

 

Like what?
I gladly give all information that I have.
Hasn't anybody got a check engine light without a code being stored?

 

this anybody has to say NO I never have (yet)

After thinking about your problem - have you considered that it might actually be the OBC that is going or has gone bad? Generally, everyone who has ever had the check engine light activate has been able to retrieve a code, and from what you describe there is a problem because the vehicle goes into limp mode, which surely creates a code. The OBC is what is activating the check engine light and putting the truck in limp mode. If there is actually a problem with your vehicle and the OBC is not recording a code - then the OBC is defective. IF - there is not any problem with your truck - and the OBC is displaying the check engine light and putting the truck into limp mode - then the OBC is defective.

If everything is as you have explained it, it would seem logical to me that the problem would be with the OBC as it is not operating as it is designed, that is to record a code when it displays the check engine light, and record a code when it puts the engine into limp mode.

Computers go bad everyday, and the ones in our trucks are exposed to some of the worst conditions.


good luck with your issue.

 

I have been working on these trucks since they were first created and I am not sure what you are referring to as the "obc". "On board computer" perhaps? Which one? The power control module?

All code readers are NOT created equal. If it is going into limp mode, a code was stored.

Someone may have cleared the codes or you do not have a scanner that is capable of reading ALL codes.

You might want to try again with a better scanner or take it to someone who knows how to do driveability diagnostics.

 

Sorry, I mean my ODB II that plugs into the connector under the dashboard.
I heard that some special devices might read the code, but where can I get a device like that? Does only the Ford dealer has the right equipment?
As I wrote, I was with 3 repair shops and none could read a code.
I didn't reset the system by taking off the battery or whatever. Still no code!

I think about ignoring it until the truck really brakes down, so a fault can be found.

 

I referred to the "OBC" and yes I was meaning an "on board computer".

While you certainly have significant more experience and expertise with these trucks having worked on them since they came out. While I agree with you that there should be a code stored - I am taking the OP at his word when he says

"The thing is I brought the car to several repair shops but none read a code from the computer"

Either they all have scanners that cannot read the code or a code is not present.

Trusting that at least one of the scanners were working properly and are capable of reading a code from his truck, there appears to be a problem in the computer - may not be the only problem he has but it is a a problem that the OBC takes actions - turns on the check engine light, puts the truck in limp mode but does not record a code.

I was taking the OP at his word and then working backwards - if as the OP states the truck is going into limp mode and there is no code present - there is a problem right there. IF the OBC was working correctly, it would record a code, if there is no code recorded I would work backwards from the computer that puts the truck into limp mode. It needs to be determined if there is a legitimate problem that should put the truck in limp mode - then if so why does the OBC not record the code for the problem? OR is the OBC defective and showing the check engine light and going into limp mode for no reason ?

You ask which OBC ? I would start with the one that puts the truck into limp mode, why doe sit do that ? Is there a legitimate reason the truck needs to be put into limp mode ?

A simple process - step by step - follow the process until the error is discovered.

 

that sounds not bad, but: which part is the ODB? is it the PCM or something?
Can I replace that?
Would be a funny effect: the part that stores faults got faulty

 

Well, the first mistake that I see a lot of people make is to assume that the OBD diagnostics are there to help find driveability issues, such as running poorly, etc. OBD diagnostics are intended specifically for EMISSIONS issues. Sometimes the code it sets helps to find a problem, but, if the problem does not cause a significant emissions issue, the OBD will NOT set an engine code, even though the engine may be running poorly. An OBD scanner only reads OBD codes. There are many scanners on the market with a wide variety of capabilities. Some can read stored codes, some can read "live data", some can read manufacturer codes, some can read transmission codes, some can read ABS codes, etc. The better "professional" grade scanners such as AE, OTC, Snap-On, and Ford IDS do a great job of assisting in locating driveability problems. They are also capable of running interactive tests. The scanner from the auto parts store......not so much. The second point would be that, if the "OBC", PCM computer is not functioning properly, It is much more likely to be a wiring problem to/from the PCM than a failed PCM itself. I see a lot of perfectly good PCMs get replaced before the real problem is identified. You can TEST or you can GUESS. The choice is yours.

 

Check the PCM's KAM power fuse. If it's open, the PCM will forget whatever was set into KAM a few minutes after the ignition switch was turned off, just as if you disconnected the battery.

It's usually a 3-5 (occasionally a 7.5) amp fuse, listed in the owner's manual as being for the PCM.

 

Without commenting on your CEL light with no error code , I heard similar problems few times in V-10/SuperDuty forums. In those cases the suspect was an "Overheated" engine going into emergency mode . Whether it was a "really overheated" engine or "behaving as if overheated" was the topic . There were discussions about testing/replacing "engine block temperature sensor" .

This is something you may want to look at if you do not have any other lead to follow.

If you have a scan gauge that provides "live data" , try to read your engine temperature (a data that is sent to the PCM ). See if that data(engine temp.) is normal.

Also, if I were in your shoes, I would review all "cooling system components" very carefully . 1-Thermostat (stuck?) 2-radiator (clogged?), 3- water pump (circulating?) , 4- Fan clutch (bad? ).

Good luck,