PCM going out?

This issue popped up a few weeks and i had created another thread on it, but just as a re-cap.


My truck will run and run all day long without a single issue or hiccup. But 4 times now its had an issue where it will not restart. It will crank and crank and crank, but won't even try fire. No codes, tach reads good, ICP and DC look good, and i originally thought it was a fuel issue so i built a fuel system. I've swapped CPS's, IDM's, cleaned every connection, and ohmed out a lot of wires that checked out perfect. Even after all this stuff, it was acting the same. Finally I unhooked the ground cables on the batteries and let it sit for a while. Came out, hooked em back up, and the damn thing fired up like nothing ever happened!

A week later it did the same thing at the farm. And again, unhooked the batteries for a little bit, and it was good to go.

2 weeks go by, yesterday at the dirt drags i put 100 miles on it getting there, made 4 passes, and a good amount of idling without a single issue. Then it hit again, right before the start of the semi-finals. Cranked and cranked and wouldn't start. This time it had a CPS code, so i tried tracking one down with no luck. By then it was too late to run so i had to drop. Halfway through that class i decided to unhook the battery cables and let it sit. Little bit later i hooked em back up and it fired right up and ran great like always.

Then this morning on my way to work i stopped to get some breakfast, and again no start. Unhooked the battery cables for a minute, and it was good to go, and has been fine since.


So is this a sign of a failing PCM?

Not getting any codes?

ghohouston said:

Not getting any codes?

Click to expand...

Nope, well aside from the occasional CPS code that comes from extended cranking. Injectors buzz great as well, just to throw that out there.

No smoke either.

Uhhh beavis, if youre getting a cps code, well... heres your sign

An extended crank does not throw a cps code

ghohouston said:

Uhhh beavis, if youre getting a cps code, well... heres your sign

Click to expand...

If its a CPS then tell my why the wiring checks out, 3 cam sensors haven't made a difference, and simply unhooking the batteries for a minute or two fixes the whole thing.


I get a CPS code everytime there are long cranks(5-6 seconds).

Strange. In my experience with literally hundreds of 7 3's, ive never seen extended cranks throw cps codes, unless the sensor was bad... did you check the female pins of the actual cps harness connector, and that the wires arent chaffed? They have been ford/intnl. Cps' s right? Hell, maybe it is a pcm issue for all I know, but a recurring cps code would def. Make me think a bad cps/ wiring to cps

Almost everytime i've swapped injectors(3 times), swapped HPOP's, swapped fuel pumps, and put an engine in it, its thrown a CEL after cranking it for a while.

2 have been Ford/IH sensors, and one was a BWD. Currently running the same sensor that was in it when this all started a while back. All the wiring looks good, when i had the engine out i went through the harness, cleaned the harness and connectors up, and re-wrapped everything with electrical tape.

And that cel hasnt been for icp? Thats what always pops up

have you noticed if the wait to start light works when it won't start? try unhooking the little red wires going to the Glow Plug Relay and see if the problem goes away. I have seen a few newer GPR's go flakey here lately

I'm going to go ahead and be the nice guy here although I am extremely hesitant to do so since I'm sick of giving out free information to unappreciative folks....

You're not taking the full five minutes and fifteen seconds to "burn" all six positions of the chip, are you?

Watch this and tell me what you see right at the initial key-up:
http://www.youtube.com/watch?v=khQY4VT4-pA

The KAM becomes corrupted after a blank boot-up and disconnection of the batteries (or just the PCM connector for a few minutes) will fix it until the next faulty boot.

Yes, I fought this for MONTHS until I found the error of my ways.

You're welcome.

I'm not burning all 6 positions, but i don't turn the knob past whatever positions i do burn. Yesterday morning i hadn't even touched the chip after i left the dirt drags and drove 100+ miles, just shut the truck off and went inside, and a minute later no start. Unless it could be an issue in the knob or something.

And the wait to start light works when it does this.

JD3020 said:

I'm not burning all 6 positions, but i don't turn the knob past whatever positions i do burn. Yesterday morning i hadn't even touched the chip after i left the dirt drags and drove 100+ miles, just shut the truck off and went inside, and a minute later no start. Unless it could be an issue in the knob or something.

And the wait to start light works when it does this.

Click to expand...

Do yourself a favor. Remove the chip and take the time to program all six positions. It doesn't matter HOW you've got the switch limited...the chip will sometimes boot in position number six regardless. You'll thank me and then you can quit ripping your hair out. I played this game for a LOOOONNNG time and sent numerous "faulty" chips and switches back to my supplier because I of these exact symptoms.....all for naught.

Good info right there.

Come to think of it, I had this issue occasionally on a chip I once had that had a No Start position on it. Have not had the issue since I removed the no start.

I've had the same problems and an electrical problem. New alternator batts cables everything was good then one day it went to s again. Would my chip be causing this being it only has 5 tunes and 6 positions I also accidentally hit the 6 position one day guess that didnt help?:fustrate:

I'll have to burn all 6 positions next time i've got the chip out, and see if it acts up again.

But its parked now, again. Vacuum pump locked up a mile from home, so i limped it in. Might have to get some new idlers as they are all gummed up from the melted rubber. I just can't win. LOL