need help plz...misfire p0354

[illegal_groundz]

03 jeep liberty 3.7 throwing code p0354 ...done replaced coil packs and plugs ..crank and cam sensor ..its not pulsing on the ground side of the number 4 coil pack ..pulled wire harness and with whrow it and cant find the prob. there and oreded a new pcm and had it programed and this still did not fix the miss ...all so checkd the timing and its dead on and pulled the vavel cover off and eveything look good ... dont know what else to do ...all and all so replaced the cats to they was clogged really bad ...

 

[TruckerKevin]

While trying to research my own problem, I stumbled upon a post similar to yours in another forum, where they ultimately found a poor ground to the main wiring harness. They reported that grinding the metal at the ground point then retightening the ground solved it for them, might want to investigate

 

[Logan Savage]

I went through the same mess , mine was also #4 , no pulse from pcm . What caused the problem in the first place was # 4 injector shorted out & fried that injector driver in the PCM . The injector gets power all the time & the signal from the PCM is a ground .
I finally diagnosed & replaced # 4 injector & ordered a plug & play PCM off ebay . Received the PCM & still had no signal for # 4 . I had already determined the wire between the PCM & injector was good . The PCM I bought was warranted so I returned it & they sent me another one . All has been fine since .
I have read that at least 50% of PCM's that are sent in to be replaced are good & the problem was a misdiagnosis . I am convinced that some of those places that sell PCM's pick them up at salvage yards or have them sent in & all they do is program them for your vehicle & send them to you without real testing & hope for the best .
All that being said , I have no idea where you bought yours but it should be warranted & if you have power to one side of the injector & the wire between the injector & the PCM is good & the injector is good , you may have gotten a bum PCM like I did .
My problem was an injector problem but you may be having the same type problem with the coil .

 

[illegal_groundz]

thanks for the replys i have done cleaned the grounds ...i thought that would help ..and the pcm come from autocomputerexchange.com the moter runs really good no smoke not tick or knock..gonna try to get a diff pcm if that dont fix it i dont know what to do besides swap motor ... are they any way i can like jump the coil pack to make it fire ....

 

[Logan Savage]

You have one cylinder that's not firing at all , right ?

 

[illegal_groundz]

yea number 4

 

[Logan Savage]

On a V6 there are companion cylinders . You could run a jumper wire from # 4's companion cylinder coil to #4's coil & it should run without missing . You'll still be showing a code though . At least that worked for the injectors . I would have to do some research to find #4's companion cylinder , can't remember which one it was off the top of my head .

 

[illegal_groundz]

ok thanks ...gonna try google to find it ...lol i am working it it right now so will will let you know if it dont mis ...thank you so much ..

 

[Logan Savage]

1 and 4 are companion cylinders in a 3.7 V6 . You should be able to run a jumper wire from # 1's coil to #4's coil & the engine should run without missing . It'll still throw a code though . At least that worked for injector firing .
Just noticed you're in WV too , where at ?

 

[illegal_groundz]

ok thanks trying it now ...will get back with you

 

[Logan Savage]

On mine the injectors all had a red wire going to one side of the injectors that had power all the time & the wires going to the other side of the injectors that went to the PCM were color coded different from one another . I am assuming the coils are set up the same . If they are you want to jumper from color coded wire to color coded wire on the coils . Do you have a meter to confirm that there is power getting to one side of the coil ?

 

[illegal_groundz]

yea i have a meter and its getting power to it ..

 

[illegal_groundz]

ok that fixed the misfire ...and like you said the light is still on ..do you thinks it the harness or the pcm ..and once again thank you ...

 

[Logan Savage]

My guess would be the PCM . What I did was traced the wire from the injector to the PCM , found a wire at the PCM connector that was color coded the same as the one at the injector , skinned the wire a little bit at the PCM connector & ran another wire from the injector to the skinned place . That eliminated it being a bad wire in the harness somewhere . If you have a meter you could skin the wire a little bit at the PCM connector & see if it would pulse between there & the hot post on the battery . It's kind of hard to do with a regular meter because it pulses so fast . A noid light works better . I also used a regular bulb like a signal light bulb & it worked . You just have to have one side of the bulb on the skinned place & the other side going to battery power . Where you at in WV ?

 

[illegal_groundz]

i am in mingo county ...just seen that your from wv to ..lol and i will try to chase it back to the pcm and try that ..i am using a led light strip ...

 

[Logan Savage]

As long as it's 12 volt it should work . I have heard about problems with the wiring harness PCM connector itself so it might not hurt to unplug it & look it over & make sure it looks alright & is plugged back in good & tight . I'm going to another site now but will check back in a little while . Good luck .

 

[illegal_groundz]

ok and thank you again ...