theft light fast flashing while driving loss of power stall

For a symptom like the opening line, my first thought is electrical related. Think alternator or charging system problem FIRST. Grounds next.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-for...-drop-test.56/

This problem could be something as simple as a loose ground or bad battery cable. Or even a bad battery.

1996+ Crank with no start check list
https://www.allfordmustangs.com/foru...nt-ignite.html

Note on Ford factory PATS system. Ford factory PATS will NEVER turn the motor off once it has started. So any symptoms that occur after the motor has actually started to run are NOT PATS related.

Pay attention to the part about fuse F2.34, F2.2, and F2.8. It would be handy to know IF any of these fuses are dropping out while the problem is occuring.

Pay attention to the part about the CCRM/PCM grounds that go around the battery to the radiator core supports.

Consider the possibility that the flashing theft light is a symptom of the problem and not the problem itself. Say for example this problem is power related and main power is being disconnected at fuse F2.34. This would cause the motor to shut off and cause the PATS system to rerun "prove out".

Do you have an ODB2 scanner? If you did it might make short work of your problem. Here's some information about an affordable Windows based unit.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-for...elm327-usb.57/

232937 said:

im thinking fuel pump ?

Click to expand...

Sigh. For the life of me I can't think of a way that a bad fuel pump would "cause" the theft light to flash.

Note, Ford factory PATS does not disable the fuel pump. It works by with holding the fuel injector pulse.

I'm a big believer in "the basics". By basics I mean "powers and grounds". If this were my car before I went through the trouble and expense to replace the fuel pump I would want to know that it really is bad. If it is a bad fuel pump there would be confirming symptoms. Think things like:

• Dropping fuel pressure
• changing Long and short Term fuel trims. One would expect the PCM to add fuel via STFT and LTFT to compensate for low fuel volume.
• Stable voltage at the trunk mounted IFS switch. The voltage at the IFS switch should be a stable battery voltage. The voltage at the battery would also be stable as well.

Besides wouldn't it stink to replace the fuel pump only to end up with the same problem?

OBTW, do the cluster gauges "sweep" after this problem happens? If so, this is a dead give away that power or ground was removed from the cluster. I feel it's possible to perform some key tests and "know" before hand if any repairs performed have a good chance of actually resolving the base complaint.