ok... I bent to wife wishes and bought a 307k miles E-350 Super Duty, Econoline, gas... yeah, funny but I still don't know the engine capacity but anyway.... after several visits to the shop, it is finally coming into shape except for the emissions data and I suspect that the PCM is either faulty or it is loosing all power when the ignition key is turned of, and as such, it would be the equivalent a battery disconnect or computer codes clear (via scan tool).

What makes me think like this is that after I ran several miles, I made back home, and read the computer. No codes, which is great and with the engine still running, the emissions failed only the tank evap system (which I just took care today). All other systems were in "Ready state".

Then I turned the ignition key off, shut off the engine, turned the key on again, read the computer emission data and bang ! Several systems in "Not ready".

I repeated this testing quite a few times, with the same result: as soon as the key is turned off, the computer looses the emission data.

Since you guys have much more experience with trucks I wanted to ask if you agree this all is pointing to bad PCM.. ?

If not, what else could be, short of measuring power to the computer on the PCM connectors... which is probably not fun because it's hard to access, etc...

Thanks for reading.

-alex

 

It helps if you provide the model year of the subject vehicle. It's mpossible to look anything up without that information.

Check the fuse that supplies the PCM KAM. It's typically a small value fuse (3-5A) that is listed in the owner's manual as "PCM" and should be ALWAYS HOT.

 

Oh sorry, I thought I had provided the minimum info but forgot to add the year: 2006... here is the partial VIN 1FDWE35L26HB.....

That is already a good clue to look at. Thanks. I do have the service manual (a big *** .pdf) bought off of ebay... says it is applicable to E-series, so I'll take a look at that specific section and fuse you mention.
Too bad this pdf has no pictures are all.. well, maybe a few ones, but not the rich amount of pics we usually find.
Will post what I find.

 

On the '06 E-Series gasser models, the PCM KAM power is provided by BJB fuse F27. That fuse also powers the EVAP CANV valve. If the evaporative emissions monitor successfully executed, it's likely there's nothing wrong with the fuse. If the EVAP CANV circuit were open due to a blown F27, you should have a DTC for that, maybe a P1451 off the top of my head.

KAM power comes into the PCM on C175a pin 45, BK/LG wire.

 

I vaguely remember my friend having an issue similar to yours. His code reader would keep resetting the ECM readiness status. Might want to look up your model and check the internet to see if there is a setting just in case.

 

Super. Thank you. Looks like I have something to do on this weekend after all

 

Ohh that would be bad... and at the same time, would cut down all headache with testing harness..... maybe could be indeed, an issue with my reader vrs this ford model but I have read my Ranger truck, Accord '98, Civic '08 and Outback '02, all read just fine. I'll see if I can find someone who could let use his reader on my truck.
Thanks.

 

I think some systems have to warm up before a ready status is achieved. Oxygen sensors, coolant temps, etc.

 

Tumbleweed1954, that is correct.
What I hinted at is that, the systems were all warmed up and "ready": I read the computer before going on a 20 miles ride - sure enough, data was not ready;
However after a 30 minutes riding I was back home, and WITHOUT shutting off, I read the computer again: all green.
Then I turned the engine off, waited like 10 seconds, turned it on AGAIN and bam: systems no ready....
So I'm not sure that the PCM is loosing the "always on" power, or it's internal memory went bad.
So, my next step would be to remove the PCM and probe the connectors for power... It's kinda an awkward place to work on: it's high up and deep in the engine compartment, but I'll try harder :-)