THEFT light flashing on 99 Explorer

Hi, all of a sudden a week or two ago the THEFT light started flashing in my 99 Explorer Eddie Bauer, when I was driving.

There are no issues other than the THEFT light flashing. The engine does not seem to be affected, no engine kill issues, no starting issues. I can start the car just fine.

I did have the fuel pump replaced recently, along with thermostat but I don't that that would be related to this.

The searches I did so far seem to indicate that the THEFT light blinking would kill the engine or prevent the SUV from starting. I have none of those issues.

Any clues on what the problem may be, or if I should ignore it if there are no other symptoms?

Normally the PATS system would disable either your fuel pump, injectors, or the starter if there was a flashing theft light at all. Is it a rapid blink?

I have run my X with a flashing theft light but that was only by directly applying 12v to the fuel pump circuit and by passing the injectors using fuel line from the test port. I used to work as a locksmith, and we saw a lot shops replacing fuel pumps and starters on Fords, when the real issue was transponder key/transponder ring/PATS system problems. Many customer paid for a new pump or starter, only to find it was an issue with the keys or the transponder ring all along.

Possibly your column needs service. The transponder ring surrounds the ignition lock inside the column, and this ring sometimes fails or becomes intermittent due to wear or bad connection. This ring reads the code (resistance) of the passive wire wound coil that is inside your key head. Sometimes the plug on the key head comes off and the "chip" falls out, but this should cause a no start. This really doesn't sound like that though, as I can't give a good explanation for why the theft light would be flashing but still allow the vehicle to start at all...unless your PCM is having an identity crisis and is failing.

Does this truck have a remote start with an immobilizer by-pass? How many keys do you have for this truck? When you insert the key and turn to run position, does the PATS accept the key and turn the light out, or does it rapid flash before even starting it? In other words, does this condition only present after starting, or will the light rapid flash but still allow you to start the truck?

If this is coming up after you are already driving the vehicle, then you probably have an intermittent transponder halo (ring) or connection that is vibrating too much on the drive. You'd better get that checked before it leaves you stranded in a parking lot next time. I would still expect it to kill the engine, but perhaps your PATS uses starter interrupt rather than fuel delivery interrupt.

Thanks for the info. I'll have it checked out. Yet another potentially expensive repair...after dumping $1600 into the SUV recently.

But you haven't answered one question. So, you just want to take a guess and start tearing things out?

Fireside3 said:

...Does this truck have a remote start with an immobilizer by-pass? How many keys do you have for this truck? When you insert the key and turn to run position, does the PATS accept the key and turn the light out, or does it rapid flash before even starting it? In other words, does this condition only present after starting, or will the light rapid flash but still allow you to start the truck?

If this is coming up after you are already driving the vehicle, then you probably have an intermittent transponder halo (ring) or connection that is vibrating too much on the drive. You'd better get that checked before it leaves you stranded in a parking lot next time. I would still expect it to kill the engine, but perhaps your PATS uses starter interrupt rather than fuel delivery interrupt.

Click to expand...

Sorry I didn't know the answers right away.

There is no remote start. I have 2 factory keys, and PATS seems to accept it as I have always used the key and never have a problem starting.

This condition happens rarely, after starting, with the THEFT light doing regular blinking, not fast blinking (from what I recall).

So no easy answers and this might require more diagnosis.

Thanks again for the help.

PATS seems to accept it? If you insert the key, turn the ignition to "RUN" and the theft light goes from steady lit for 3 seconds to out...then it's accepted.

If your theft light flashes like 2-3 times a second or stays lit, then there is a PATS issue. Other than that, I don't know. There might be a PATS related trouble code there. Have you read the codes?

Thanks. THEFT light does turn off, and I can start the car at any time. It only starts flashing after I have been driving for a while. I have not pulled any codes yet but that will be the next step.

99EBEXP said:

Thanks. THEFT light does turn off, and I can start the car at any time. It only starts flashing after I have been driving for a while. I have not pulled any codes yet but that will be the next step.

Click to expand...

Just be mindful of the transponder halo surrounding the ignition switch and that this is a problem in some Fords. It can leave you stranded with a no-start at any time. When I worked as a locksmith up until about 2005, we saw a lot of no-starts due to transponder halo failure, and the people and their mechanics were beating their heads against a wall trying to figure out why a new starter or fuel pump didn't fix the issue. Mostly on the Ford Focus, which were total crap the first few years they made them, and Ford literally had to pay us to go around replacing those things for stranded people who owned a Focus. We did see Mustangs on occasion with the same issue, and every now and then an F-150 or Explorer.

IF you flashing during the running is at the same "pace" as when your truck is "just sitting" (ie not on), then it is likely your truck has "lost" its "sense" that your key is in ON in terms of the PATS system only.... my uneducated guess. I would look at the wiring shematics at those areas to see where that is.

Ok I found out what the issue is.

It turns out my battery was starting to wear out / die. Other symptoms I noticed was the garage remote on the visor was not transmitting as effectively, and the dash lights were dimmer.

Once I replaced the battery, all is well. There is no more THEFT light blinking, dash lights are bright, and the garage remote on the visor is working well again.

Pretty interesting that a weak battery can cause these symptoms. I guess the alternator alone does not provide sufficient power for all of the auxiliary systems.

99EBEXP said:

Ok I found out what the issue is.

It turns out my battery was starting to wear out / die. Other symptoms I noticed was the garage remote on the visor was not transmitting as effectively, and the dash lights were dimmer.

Once I replaced the battery, all is well. There is no more THEFT light blinking, dash lights are bright, and the garage remote on the visor is working well again.

Pretty interesting that a weak battery can cause these symptoms. I guess the alternator alone does not provide sufficient power for all of the auxiliary systems.

Click to expand...

no it doesn't. If you run too much ****, eventually the alternator can't keep up and you spend too much time discharging the battery. You wear it down enough times, and it fries a cell and won't hold a charge. That's why a lot of high electrical demand custom jobs require dual batt/alternator.

Still could be your alternator or something in the charging system if the new batt starts to degrade too soon.