Theft light, stall, 2003 taurus

[madeintheusa]

2003 Taurus, 3.0 duratec flex, 30K. While driving at various speeds the theft light flashes for a split second and the car starts to stall before resuming normal operation on its own. The rpms drop off, and power is lost for a split second. This is getting more frequent and happened five times during a 30 mile drive. The original Ford key is being used. My scan tool reveals no codes. I understand that there may be anti-theft codes that my scanner cannot read. Any help would be much appreciated.

[shorod]

The antitheft system should not cause the car to stall once it's started and running. I think you have an electrical system issue that is causing the PCM and/or PATS/SecuriLock systems to lose power. I'd start by making sure the battery cables are clean and tight at the battery and at the alternator. Make sure the power cable connection is secure at the power distribution panel. Make sure the PCM relay is secure and that all fuses are also inserted completely into the fuse panels.

How long have you had the car? How many keys or trinkets do you have hanging from the key ring?

-Rod

[madeintheusa]

I've had the car a couple of years. You are right about how the anti-theft shouldn't shut down the car once running. The car has never had a problem starting. I did find a loose and slightly corroded battery cable. I cleaned and tightened that tonight. I will post if that clears things up. Thanks for your input.

[madeintheusa]

It has been two weeks and the problem appears to be resolved. The only thing that I found was a loose positive battery cable connection at the battery. I still don't understand how the loose cable would cause a stall since the alternator should be supplying all the necessary power.

[shorod]

Thank you for the follow up post!

The alternator supplies unfiltered current to the charging system. The output from the alternator can be quite noisy and by design will have a multi-phase (typically 3) alternating current (AC) fluctuation. Electronics don't like noise. Noise can cause logic level transitions in high speed electronics as well as cause what appears to be low voltage to the electronics. The car battery acts like a large capacitor and filters the noise and AC in addition to storing A LOT of charge for the high demand, low engine speed situations such as sitting at a stop light with the brake lights on. Other high demand situations would include the A/C compressor clutch kicking in and loading the system in addition to the IAC attempting to speed the engine up, etc.

-Rod

[efw58]

I have a 2003 Taurus. I have been dealing with Anti Theft System issues for several years. My problem mainly occurs in hot temperatures. The car either will not turn over or the theft light begins flashing and the car stalls. I found a you tube video of a Ford Dealer with a Ford Focus with the same problem. His solution is found on You Tube with the title - Ford Focus No Start Theft Light Blinking Easy Fix. It is an easy fix. I tried this solution and have had no problems over the last two weeks in the heat. The ground on my car actually grounds to a painted area on the car body. I just sanded the paint and the ground and used the dielectric grease just as he says.

Hopes this helps.