Failsafe Engine Prog message with trifecta
 

Was driving today and got this message "Failsafe engine Prog" on the dash with the trifecta lights. I should have saved the error codes but was wondering if there was a common culprit for this. If it comes back I'll post the error log from the DME. Battery is a Deka AGM about 5 years old (I saw on another post that a weak/old battery can cause this issue).

If it clears it is likely alternator.

Monitor voltage live and see what happens when you come to a stop and go from power on to coasting.

If the voltage dips below 12.5 almost always alternator failure and the first sign is often trifecta and trans failsafe even before you get battery light for some reason.

Yeah it cleared when I stopped and restarted the vehicle.

Learn to use the hidden menu to monitor realtime voltage and see if you see a dip on off throttle. Both of our 01 models suffered this fate about 150-170k on the clock.

I rebuilt the voltage regulator with a $20 kit

Bad ignition switch can also cause this.

Where is the hidden menu?

What troubleshooting would you do to narrow it down, if it were a bad ignition switch?

Lots of things can cause the trifecta and "engine failsafe prog."

When my alternator went, it did not trip this code. (Neither time)
When my idle control valve was faulty, it tripped this code.

Pretty sure I saw it for other reasons over the years too, and saw it happen spuriously (i.e. without a reason).

+1, don't go assuming anything, you can do a quick check with a multimeter for charging voltage and maybe get yourself a cigarette lighter plug if you really want something handy to rule out charging voltage problems.

Difficult to diagnose 100% without taking it apart or renewing it. One test you can do is to open the sun visor vanity mirrors. Strange things can happen, when the light activates. If you have diagnostics it could show on some modules a code for temporary missing Terminal R or Terminal 15 voltage supply.