2002 2003 2004 2005 Ford Thunderbird 3.9L PCM ECM ECU

Hiatt Riot · Dec 29, 2023

doug7740 said:
In reply #15 of this post, you stated that It was the connection to backup lamp and relay where the short occurred and that you checked every fuse and diode in all 3 fuse boxes. Now you tell me that you you couldn't open the trunk to check the battery. That means that you never checked the fuses in the rear power distribution box. Chances are that one of those fuses are blown or your battery is too weak to supply the proper voltage to the control modules.

In the future, in the event of a battery failure you can open the trunk by using the master key on the key cylinder located behind the driver seat.

doug7740
1955 Thunderbird Blue

I had power at first and did check every single fuse in all 3 boxes with a meter and replaced the one bad backup fuse in the trunk. A day later after closing the trunk the battery was drained and the key wouldn’t open the trunk. Hard crowd here.

doug7740 · Dec 30, 2023

I never meant to come off as hard, I only meant to help you with your problem. You will find that this forum is one of the best on the internet and the members of this group are very knowledgeable.

As far as the key not opening key cylinder located behind the driver seat, did you try all of the keys that came with your car? The reason I am asking this is because my car came with two master keys and a valet key. The valet key is a coded key and will start the vehicle and unlock the driver's door, but it will not unlock key cylinder located behind the driver seat or the trunk release button on the driver's door.

doug7740
1955 Thunderbird Blue

Hiatt Riot · Dec 30, 2023

Hiatt Riot said:
I had power at first and did check every single fuse in all 3 boxes with a meter and replaced the one bad backup fuse in the trunk. A day later after closing the trunk the battery was drained and the key wouldn’t open the trunk. Hard crowd here.

It seems probable that when I replaced the backup lamp fuse, that circuit, which was my only splice in the car wiring, probably is what drained the battery and is likely still a dead short.

doug7740 said:
I never meant to come off as hard, I only meant to help you with your problem. You will find that this forum is one of the best on the internet and the members of this group are very knowledgeable.

As far as the key not opening key cylinder located behind the driver seat, did you try all of the keys that came with your car? The reason I am asking this is because my car came with two master keys and a valet key. The valet key is a coded key and will start the vehicle and unlock the driver's door, but it will not unlock key cylinder located behind the driver seat or the trunk release button on the driver's door.

doug7740
1955 Thunderbird Blue

Thanks, and no, I didn’t know that one of my two keys might be valet. I’m a new owner. I guess I need to take the other key to the shop that now has the car. This has been extremely frustrating for me, so my patience was a bit worn and it didn’t help for moderator to vaguely complain about my post title that I still don’t get.

Thunderstruck2004 · Jun 5, 2024

Hi! My 2004 Tbird has been shifting hard from first to second and second to third. I took her to the mechanic shop, where they told me the transmission fluid was fine, and that it was a problem with the PCM. They said they do not replace PCMs unless they are new old stock from Ford (which at this point is not available) because reprogrammed PCMs can begin to have other issues within months or years, which renders them hard to be able to stand behind as a repair by the shop. I have found places online where I can purchase a new reprogrammed PCM, but my question is if I purchase this and install myself, if other things begin to go wrong with the Tbird as a result of the new PCM, can I unplug the new PCM and replug with my old (current) PCM, will it go back to just having the hard shift?

I am weighing whether I want to live with the hard shifting but being able to drive it, or if trying to repair it risks bigger problems rendering the car undrivable.

Thanks!

biddle · Jun 5, 2024

Thunderstruck2004 said:
They said they do not replace PCMs unless they are new old stock from Ford (which at this point is not available) because reprogrammed PCMs can begin to have other issues within months or years, which renders them hard to be able to stand behind as a repair.

Lame. Find another mechanic. They just don't want to fool with it and quite frankly, they could even be wrong about what the actual issue is. Check post #1, those are also updated. Message them with any questions you have.

Also, sometimes the software simply needs updated- Post in thread 'Transmission shifting rough 2004 Thunderbird' https://forums.fordthunderbirdforum...ifting-rough-2004-thunderbird.7821/post-50651