After swapping the engine from a 5.4L to a 4.6L engine is in fail safe mode, is there a way to bypass this?

KIMBERLY1227

MEMBER
2004 FORD F-150
4.6L
V8
4WD
AUTOMATIC
68,000 MILES

I've got the truck listed above (Lariat) I took the 5.4L motor out and replaced it with a 4.6L motor. I then hooked everything back up, and put everything back, ect, and now it will not crank. It's in engine fail safe mode (the red security light is flashing) and it won't turn over or crank or nothing. What's the process of bypassing this?

Tuesday, October 12th, 2021 AT 5:25 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,097 POSTS

Hi,

If the security light is on, it sounds as though there is an issue with the PATS (passive anti-theft system).

There is not just one module controlling this circuit. The system includes PCM, Central Junction box, and the Transceiver. Were any of these things changed when you changed the engine size?

If so, PATS security access must be granted to erase ignition keys, enable/disable unlimited key mode, and enable/disable the spare key programming switch. It will require a scanner that can communicate with the PATS circuit. This isn't something that can be bypassed.

If you look at the pics below, they provide the directions specific to the procedure. Take a look through them and let me know if you have questions.

Take care,

Joe

See pics below.

Images (Click to make bigger)