I Have two 2004 screw lariats. A couple of months ago I received a "Engine Fail Safe Mode" message with the truck that I drive daily. When the message was showing the engine ran like it was cutting out cylinders intentionally with the ignition. The message went out and the engine ran fine. This happened a couple of times so I asked my dealer about it and his responce was "It's not showing any codes and it seems fine now" yeah thanks a bunch! Now I was just informed that the other truck is experiencing the same problem. Could someone please explain to me what the heck is going on?

Thanks

 

Don't know if I can help much, but the fail safe mode is when the computer finds a problem with a sensor that it uses for fuel mixture, trans shifting, etc. that is out of range so it ignores it and runs in "failsafe" or "limp" mode. Did your check engine light come on? If not, then there isn't much the dealer can do unless it acts up on them when they have it. Ask me how I know! Happens at work all the time. Cust tells me it does it everytime I get in it. I ride with the cust, and guess what, nothing. Granted, this is an extremely crude definition of limp mode, but I hope at least I may have helped you understand the concept.

Robbie

 

Problems with the cooling system can cause the engine to go into the failsafe mode. If the PCM sees a overheat condition, then it randomly cuts out certain cylinders to allow you to "limp in" for service. Since your Truck was not overheating, the coolant temp sensor may have malfunctioned. That should have set a DTC though.

 

I have a 03 screw, and it does have a fail safe mode, but it only does it if there is a total loss of coolant. It will only use half the cylinders for ignition and the other half for air cooling. I know there are probably a lot of differences between 03 and 04 f-150's, but I would assume that this is one thing they have in common. You need to refer to your owners guide on this problem. I say that because my owners guide does talk about the fail safe mode. On your 04 there may be more reasons for it going to fail safe than just a coolant loss, but I would check to see if your not too low on coolant. If you're ok, then I would suggest resetting your PCM by disconnecting the battery. I'm not sure that this would help, but it couldn't hurt to try.

 

I stopped to help a man in a van on the side of the road with the hood open. He was looking at the engine, said it was showing overheating but didn't feel hot at all, and was going to keep driving. The engine really did feel barely warmed up. I put a rag over the radiator cap, twisted just past the lock and let it up very slightly. You could feel it and hear it boil in the engine. I said, well it must be hot. He said, How could that be, they just replaced the water pump yesterday. I wondered how to break it to him, someone sold him a waterpump to fix a head gasket problem.

I've wanted to tell that story since Labor Day. Anyway, does the engine indicate it's hot? Does it feel hot? Do you have the experience to tell if the engine's hot by cracking the cap without getting scalded. If the engine's overheating, nothing else seems wrong, and the engine feels cool, ask someone to check for a head gasket leaking.

File this under longshot. Listen to everyone else first.

 

I don't believe that my particular problem has anything to do with overheating or coolant level. The engine goes into the fail safe mode as soon as it is started and there is not even any heat in the engine yet. Neither truck that I have experienced this with has ever been a drop low on coolant or shown any indication of any problem after in returns to normal mode. Both trucks experienced the problem with only between 5,000-10,000mi on them and both run like champs 99.9% of the time. It doesn't really present much of a problem other than peaking my curiosity and the very rare instance when this causes the trucks to temporarily run like sh##. I can definately live with it but for some reason it just doesn't seem normal to me.

 

Judging by the model year of truck you have listed, I would think that it should still be in warranty, unless you've already gone over on the miles. It is possible the PCM may have logged a code on this problem. I would take to the dealer to have it looked at.

 

Well, since you have already taken it in and it had no codes, then you might have to leave it there until it cools down and then start it up and hope that it will do it in front of them......

Strange that something like that would not throw a code... Even if the light went out, it should still indicate that there was a fail safe mode activated at some point in time.......

Good luck!

Mitch