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1997 Ford F350, 7.3, 2 wheel drive. PCM part number F6TF-12A650-AYG.

OK the question is how to diagnose the PCM without codes due to the battery being dead?

I have it out of the truck and was hoping to see diagrams or schematics for use of a multimeter. I looked at all the fuses, sensors, etc. I need to know how to do this because the PCM is to expensive to get a diagnosis from places and/or I have to R&R the part.

That still may not be the issue. If I have to put it back in or anything I will do it. Please help. I did hook it up to a diagnosis reader, and tried a few times to erase codes that where not there.

Also, it gave me an error trying to erase the codes. I also tried this test on 4 other vehicles with this computer and it would erase codes even though there weren't any, without error.

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  • The error codes reside in volatile memory. When you unplug it from the vehicle power, it will lose it's memory within (usually) 30 seconds. What ever was there will be gone. I'm not really sure what you are trying to accomplish if you are not seeing any codes or anything else when you have tried to read/erase codes in the past. If you plug it in and it isn't showing any issues, then how do you know there's a problem with the PCM? What exactly is your issue to cause you to think the PCM might be at fault?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 4 '16 at 20:13
  • Not to sound rude at all but it does say I have checked everything else also I stated that I know there are no codes due to the battery is was checking for any kind of communication
    – Michael
    Mar 4 '16 at 21:05
  • There is no fuel and no oil being pumped the sensors for drivability are all good and I don't have the money for either the dealer or the computer to do the easy diagnose.
    – Michael
    Mar 4 '16 at 21:08
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    You cannot use a multimeter to diagnose the PCM. Without codes, it not being hooked up to a battery and into the vehicle, you will never be able to figure out what is wrong with the vehicle, unless you have a specific PCM tester. If you have checked everything else, then your next step is replacement. Try Craigslist or a junk yard. I don't know what else to tell you.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 4 '16 at 21:23
  • Like I said I will put it back in so I can check it have tested every senor on the truck. How about this I'm not a diesel tech by all means. Can someone point me to a diagnosis procedure? I will start over.
    – Michael
    Mar 5 '16 at 21:05
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It's very hard to tease out what your actual problem is. Here is what I've figured out. Your truck won't start and you have no communication with the PCM. This makes you think that the PCM is bad. How am i doing?

First, a PCM can't be diagnosed outside the vehicle without a big complex setup that simulates all of the vehicle it should be hooked up to.

Second, the list of things that need checked before condemning a PCM is a mile long.

With the PCM connected to the vehicle every singe power and ground needs verified directly at the PCM (there will be more than one of each). You would be surprised how often a broken wire leaves you walking.

With the PCM connected to the vehicle every critical signal that the PCM needs to start needs to be verified. I would start by verifying the communication lines from the DLC to the PCM have good continuity.

Finally, the output signals need verified. Is the PCM trying to control the injectors or not.

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