2003 Grand Marquis was perfect BUT sat for a year - now mechanic says needs POWER TRAIN Control module

Asked by Feb 26, 2015 at 09:47 AM about the 2003 Mercury Grand Marquis LS Premium

Question type: Maintenance & Repair

2003 Mercury Marquis with 20k miles was pristine but then sat outside for a year - now wont start and FORD says it need a $985.00 power train control module.....Step one: Just to see if there are other issues.....Sound about right?

10 Answers


This is probably from the battery going completely dead and now the car has no communication with the module; they're right so far as there being no way to determine other issues if the obd2 system won't communicate. Maybe a used one is available for the car.

Thanks Chris for replying. Wouldn't Ford dealership be able to hook something up to communicate/diagnose? ford says used is 698 no warranty.


Did you take this vehicle to a Ford dealer or an independent mechanic?

It is currently at Ford dealership waiting on go ahead to order module



Certainly it is possible that the ECU is bad, but I personally would be very surprised that it is bad. The Ford dealer is the best place to have this work done and the list price for the ECU is just over $700.00 with your old unit as an exchange. Tasca parts online (a large Ford Dealer) shows the ECU part number as 3W7Z-12A650-BEB and they show it to be discontinued. Perhaps your Ford dealer has located a remaining part sitting on a shelf at another dealer.

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Joe, sometimes a bad module prevents codes from being extracted. That's why the dealer has said that it needs the module first, before seeing if there are other issues, unfortunately.


Wow that does sound kind of weird with only 20k on it doesn't seem to me like the module would just go bad I'm not real familiar with Fords computer system but I guess it is possible for it to lose its memory but it seems to me like the Ford dealership should be able to reflash the computer (they may be just trying to sell you a computer module) I would get a second opinion different dealership and check with independent garages and see if they heard of anything like your experiencing

1 of 1 people found this helpful.

I smell a rat. my 2002 sat for years with a dead battery, and it fired right up, took a while for the codes to re-set.

1 of 1 people found this helpful.

If the ECU is bad it is just a coincidence, letting a vehicle sit for 1 year will not ruin the ECU even if the battery does run down. I wonder if a mouse or mice ate some of the wiring. I would take a really close look for mouse damage.

1 of 1 people found this helpful.

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