Help please-Theft light

Here's some information that may help.

1996+ Crank with no start check list
https://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

Disabling PATS is just not a simple, "cut this wire" to disable. It's normally done with a PCM update.

Did the PATS system work before the work was done? From the crank with no start check list note how a POWER problem can present as an apparent PATS issue.

If this were my car I would look for a POWER problem from a missing ground. Especially after a large amount of work. Pay special attention to the grounds around the radiator core support. In addition the PCM/CCRM ground that goes around the battery.

There's also a ground strap that goes from the left hand motor mount to the car's frame rail. This is frequently damaged during a motor install. Double check this ground strap is still in place and has a good connection.

Has power been confirmed inside the Battery Junction Box?

Pamela70 said:

Yes it worked before it was parked for repairs

Click to expand...

So all the more reason to first rule out a problem that is a result of the large amount of work done during the repairs. Double check your work.

Don't ignore the part about the grounding strap between the left hand motor mount and the car's frame rail.

CONFIRM there is key on +12 volts at the MAF Red wire. Use a KNOWN good ground. IF no power, confirm the EEC fuse in the battery junction box is good. The motor will never start unless there is key on +12 volts at the MAF. Optionally you could test the Red wire at each fuel injector.

If unable to find an obvious problem, here's some information on how to perform a voltage drop test. It's a technique that works regardless of the car. Need to confirm the ground to/from the PCM and/or CCRM (this ground is the same as 1996+ model years).

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