Recurring P1451 code.

[Bitter]

Have replaced:

FTP sensor after seeing it not rise or fall within specified range
Canister vent solenoid after seeing it not always close when grounded manually
charcoal canister after seeing some of the charcoal outside of the canister and in the CV solenoid.
smoked the system to verify no leaks.

have verified integrity of ground wire (ppl/wht) from PCM main harness to solenoid
have verified power feed to solenoid as well.

faulty PCM?:thumbdwn:

 

[pj8847]

Welcome to the forums!

A good start would be to let everyone know the vehicle info.
Would help greatly in determining wiring and component layout, etc...

But just off the top of my head, if you replaced the valve, and it passes inspection (I know you replaced it, but new parts can be bad, so check that resistance is withing spec, and valve functions normally), and you have traced and tested all wiring and found no shorts or breaks anywhere, it is quite possible a PCM issue... but more info is needed before jumping to that...

 

[Doubt Incarnate]

what is the code exactly?

 

[pj8847]

P1451 EVAP Control System Canister Vent Solenoid Circuit Malfunction

 

[Cobraguy]

It is so rare for a PCM to be bad. It happens...but not very darn often.

I remember when Ford collected the ECM's that had been replaced under warranty and took the time to actually test them. 15% had been zapped by improper grounding practices by techs. Less than 2% were actually bad. The rest were misdiagnosed.

 

[pj8847]

It is so rare for a PCM to be bad. It happens...but not very darn often.

Agreed, that is why more info is needed, and more tests, like running "jumper" wires directly from the pcm to the valve to rule out an intermittent short somewhere within the harness that can't be seen, maybe a bad "new" part, etc...

The OP appears to be on site since posting, but hasn't responded yet...

 

[Doubt Incarnate]

how would it detect a malfuntion? maybe if the valve is working properly but there is a problem after the valve the pcm would just assume it isnt working.

 

[Bitter]

i went through the gambit of tests outlined.

the code would set immediately upon running the KOEO or KOER test routine with the new solenoid, not intermittently. power was verified to the solenoid, however we never saw the PCM ground it.

couldnt find a 5spd pcm to test with so we grabbed an auto pcm, and while it threw every imaginable transmission code it however did NOT immediatly throw a P1451 code.

new PCM is coming in next week, hopefully this is the solution. the one removed from the vehicle was an aftermarket rebuilt unit.

96 5spd explorer sport, 4.0 V6, 150Kish miles.

ran the circuit tests, things like checking for voltage between pin 67 and 51 and 103, measuring the resistance of the power feed wire and ground wire, etc etc. about 12 tests in total outlined, i'd be insane if i could remember all if off the top of my head. if you guys are interested i can scan the printouts which outline the tests performed should anyone come up with this code.