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I bought a 2006 F150 5.4, 4 wheel drive, with a problem, it won’t start.
When you turn the key, the gauges come on, but when you try to start, it doesn’t turn over, it doesn’t click.
I suspect the PCM computer, since it’s loose, someone has taken the bolts out. Before I buy a new/used one, I'd like to test it first.
I have a friend with a 2006 F150 5.4, 4 wheel drive, Lariat.
Question: Can I swap/use the PCM from the another, similar F150?
My PCM part number: 6L3A-12A650-BSA
Loaner PCM: 6L3A-12A650-BPA
Are these 2 close enough that I can temporarily swap them?
The basic test/question would be: Does the other PCM turn the motor over?
If it turns the motor over, then I would assume the PCM is bad and buy another exact model PCM.
Would this work for a test?
It gives a P0351 code - Ignition coil or Primary Circuit Malfunction, which could be the computer.
The PCM has to be matched to the coded key to get it to start.......... so no, it will not work..
When you turn the key to ON and not START, you should get the THEFT light to come on for 3 seconds, then it will go out after the key and PCM have MATCHED each other... Does that happen ?
351 code is probably the plug on the coil... not the computer.
but when you try to start, it doesn’t turn over, it doesn’t click.
A P0351 won't cause that symptom, something else is going on.
Start with the basics: Does PATS prove out properly? Observe the THEFT light.
Are these 2 close enough that I can temporarily swap them?
The basic test/question would be: Does the other PCM turn the motor over?
If it turns the motor over, then I would assume the PCM is bad and buy another exact model PCM.
Would this work for a test?
It can, but you're going to have to "cheat" a bit. There are a couple of ways to do it.
1. Swap the ignition cylinder along with the PCM from the loaner. That way, the already programmed key will match its original PCM.
or, if you don't want to mess with having to swap the cylinder also,
2. Have a plain copy made of the current key for YOUR truck.
3. Swap in the loaner PCM. Make sure you have one of its keys that worked properly before removal.
4. Insert the plain key into the ignition cylinder.
5. Hold the loaner key against the head of the plain key and rotate the key.
If the loaner key is successfully read, PATS will prove out and allow the engine to crank and, maybe even start and run.
Thank you very much to Steve and SHO for your response!
Thanks for the good tip to check the PATS.
Answer: Before I put the key in, the red light is slowly/normally blinking.
Then, I put the key in, turn it to ON, and the red light keeps blinking the same, slowly.
It does NOT come on for 3 seconds.
I think this is where I should start, with troubleshooting. This seems to indicate a PATS issue.
The manual says, if there is a problem, the light will flash rapidly or glow steadily.
Mine isn’t doing either of those, when I turn the ignition on.
It just keeps blinking normally, as if I had not turned the key on.
But the dash lights do come on when I turn the key ON.
Does that help with troubleshooting? What do you think that means?
Thank you for the info that the computers are close enough that the other one should work in this one.
My thought was just to see if it would turn the motor over, with the new/other computer, but I like your idea to make a key copy without the chip and hold the working key with chip from the other pickup against the key head.
Answer: Before I put the key in, the red light is slowly/normally blinking.
Then, I put the key in, turn it to ON, and the red light keeps blinking the same, slowly.
It does NOT come on for 3 seconds.
I think this is where I should start, with troubleshooting. This seems to indicate a PATS issue.
Most likely, the apparent PATS issue is a side-effect of whatever is wrong with the PCM . For example, if the PCM does not power up properly, the results will be the same as you reported.
When the key is turned from OFF to RUN, what is the state of the odometer and the check engine light?
Are you able to establish normal communications with the PCM via your scan tool?
Do keep in mind that, if you eventually replace the PCM, you WILL have to reprogram the PATS system as part of the installation. Failure to do so will result in a truck with a new PCM that still will not start or run.
When I turn the key on, the odometer comes on. The check engine light comes on,
FORScan says: Found module: PCM-Powertrain Control Module
Next line: PCM: Unable to read DTC.
So it's not giving me any clues for codes.
Any thoughts on why that is, how to solve that?
With that additional information, I'd lean strongly towards a failed PCM. It's powering up but, as you can tell, something is preventing both internal communications and CAN-bus functions.
I would recommend checking the CAN-bus for proper termination and for shorts to power or ground before condemning the PCM.
Not that I no my b--- from a hole in the grd . I don't see a failure of the pcm . The start relay must receive a grd signal to get it to pu which comes from pcm . The hot side 13vdc position is controlled by shift lever position etc .
Check for good start relay and is 12dc positive getting to relay . The main cause of pcm lack of ground signal is pats system not satisfied '
The start relay must receive a grd signal to get it to pu which comes from pcm .
Look closer at the stated symptoms. He's got neither a successful prove-out nor indicated failure of PATS along with a "no-crank" symptom. It's like the PCM is out in never-never land. That would tend to suggest that something is causing it to hang somewhere in its initialization cycle. Whether that "something" is internal or external is to be determined.
Since PATS is not proving out successfully, checking at the starter relay isn't indicated, the PCM isn't getting far enough into the process.
I realize a lot of what you are saying . I just gave him a diagram to pin point the lack of signal to confirm a diagnosis . We are not there to double check or observe . He can bypass a lack of a signal if he chooses to prove the rest is complete or not . Being a troubleshooter for a large electric company gave me a lot of experience in this as I tried to talk electricians from remote sites thru stuff until I could get there. One of which was a loss of cooling to reactor at a nuke plant ,it came out okay . No I don't think I'm all that .
Just old and experienced still learning -helping if I can .
your diag may be correct . I have not had a lot of exp with a failed pcm in vehicles . I have observed a lot of guys blaming the pcm for everything .
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