Stumble/Miss/Hesitation

[Jackpine]

Originally Posted by BigSur

Wow...what is that exactly? What happens when a truck goes into fail safe mode?

"Failsafe" is actually designed to get you home if your truck engine overheats. (It's also known as "limp home mode"). Basically, the PCM shuts down spark and fuel to half of the cylinders so that the engine can run cooler.

As I said, it's supposed to be triggered by overheating, but it seems that the PCM can apply this strategy any old time - possibly caused by a false sensor signal. If you're really paying attention, you'll see the temperature gauge peg on full hot as it goes into failsafe mode. The PCM is actually moving the temp gauge there, since it is not actually telling you what the coolant temperature is (there's no sensors for that value - it's inferred by the PCM from the Cylinder Head Temperature).

The fact that an engine shutdown and restart often clears this condition is almost a sure sign (to me) that some sensor is malfunctioning.

- Jack

[mjphillips1981]

Got the fail safe error again today. I immediately checked for codes and this this is what I got. And again I turned her off and started back up and all was good. Same I was leaving work and as soon as I pulled out of the parking lot bang, fail safe.

P061B Internal Control Module Torque Calculation Performance

Anyone have any idea what this is?

[mjphillips1981]

After reading a bit in the forum, I see that this code may be related to the tune. Everything that I have seen says canned tunes, but I am running a custom 87 perf tune. Please help!