PCM problem

[nz225]

I need some help. I have a 99 250 psd six speed with 240,000 miles. Yesterday, the truck wouldnt crank over BUT the "wait to start" light would come on. I started by checking out all the fuses, key out of ingnition, with an ohm meter. I then realized it was the clutch safety switch, fixed that problem. However, now the "wait to start" light wont come on but it cranks. No fuses are blown. No control voltage to glow plugs. No electronic fuel pump voltage. I think its the pcm.

Any ideas?

[alabamafrog]

Make sure its not a blown fuse or power loss to the PCM before replacing the PCM. I can't remeber the fuse that poweers the PCM but I think it is under the hood. I got my newer PCM from car-parts.com for $75 delivered.

[nz225]

with the new pcm, does ford have to recalibrate it? or is it ready to go out of the box?

[alabamafrog]

My "new" one came from a junkyard, contrary to what Ford will tell you most of them are interchangeable. If you want to be really sure everything stays the same then get your calibration code off your old computer and get another one with the same 4 digit code. I believe that any computer in the same family would work though. I got a used computer from an 01 and put in my early 99 and it works fine. I know the automatics can’t use a manual computer but I ‘think’ the manuals can use either.

[alabamafrog]

Here is an example of the sticker you would find on your computer

The PMT1 is the calibration code and the DPC-422 is the family, at least thats what I think they call it.

[stewy]

On my early 99 the fuse that effected the wait to start light was micro fuse #30 located under the dash, it was a 30 amp. It was the same fuse on the fuel bowl heater that was blowing the fuse. Good luck

[nz225]

To update: I do have the early 99 psd. I have previously unplugged the fuel bowl heater, and the fuse isnt blown. On both sides of the #30 fuse there are 12 volts. So, unless there is a break in the line between fuse and pcm, i guess it would be safe to say i need a new pcm.

Thanks everyone.

[CoalRollinRoosterCruiser]

Originally Posted by alabamafrog

My "new" one came from a junkyard, contrary to what Ford will tell you most of them are interchangeable. If you want to be really sure everything stays the same then get your calibration code off your old computer and get another one with the same 4 digit code. I believe that any computer in the same family would work though. I got a used computer from an 01 and put in my early 99 and it works fine. I know the automatics can’t use a manual computer but I ‘think’ the manuals can use either.

Manual's can't use either i dont think. Pretty sure they have to use a manual PCm, or thats what i told at least.

[SCUFFY828]

i believe i would do more diag before replacing the pcm, few and far between the pcm goes , bad , half of them that get replaced are replaced on a guess and really dont need it , so what im getting at , just make sure first, no wait to start light means no power to the pcm, dig a little deeper

[nz225]

where to start digging? thats the problem.