P0351 Problem
Thread Starter
|
Freshman User
Joined: Apr 2013
Posts: 32
Likes: 0
P0351 Problem
OK as you most know I have been having trouble with a Missfire on my truck. The PCM keeps giving me a OBD code of P0351. I have driven the truck the last few days with out running the AC and I have no problem with the truck. It runs great. When I turn on AC about 20 mins into driving my truck starts missfireing and I get the p0351. Was wondering why the Running the AC would cause this?
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
It's cylinder 1 primary circuit issue.
Being up front on the pass side, look for any possible condensation/coolant or ? falling on the coil from some source nearby.
You should at least pull the coil and look down into the plug well for some accumulation.
Next, there has been reports some time ago that seem to indicate the A/C plumbing back at the firewall may have some 'surface charge' influence on the harness passing very close by. For this, use a tie wrap to keep the harness at a distance and see if that might be the problem.
Otherwise I don't know of an association between the cylinder and A/C.
Good luck.
Being up front on the pass side, look for any possible condensation/coolant or ? falling on the coil from some source nearby.
You should at least pull the coil and look down into the plug well for some accumulation.
Next, there has been reports some time ago that seem to indicate the A/C plumbing back at the firewall may have some 'surface charge' influence on the harness passing very close by. For this, use a tie wrap to keep the harness at a distance and see if that might be the problem.
Otherwise I don't know of an association between the cylinder and A/C.
Good luck.
Thread Starter
|
Freshman User
Joined: Apr 2013
Posts: 32
Likes: 0
Thanks. Will look into that. I know there is a Plastic Shething that goes around Most of the Wires coiming out of the Harness. And I didn't think there would be a corilation with the ac and the problem I had. Was just somethng I observed. Have not found any moister in the plug well or on the COP or anything like that. Will continue to to check it out. I know when it goes to Missfireing and having this problem the AC system is shut down. I'm told by Ford that this is designed into the PCM to conserve power. The problem is just getting frustrating. Tried everything except replacing the PCM and i'm considering doing that next.
Thread Starter
|
Freshman User
Joined: Apr 2013
Posts: 32
Likes: 0
Bluegrass_7 another question for you or anyone that knows. When I was checking all the wires out today on my truck I noticed on Cylender 2 that the wires going to the Fuel Injector Connecter was knicked..ie small spot of bare wire was showing. Could this cause a ground that might make Cylender 1 missfire? Just Courous.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
You want to be very sure it's not something outside the PCM because it's an expensive change.
To test for the PCM or the harness to it, test for the ground being pulsed to the coil from the PCM solid state switch with the motor running.
A second test is with an Ohm meter looking back at the switch with the motor off.
It should measure about 10,000 ohms +/- .
If to high it's in trouble.
If to low it's in trouble.
This normal resistance is built in to make this outside test determination.
.
If you replace the PCM, it requires reprogramming and two keys to complete the job.
The end result in dollars is high.
To test for the PCM or the harness to it, test for the ground being pulsed to the coil from the PCM solid state switch with the motor running.
A second test is with an Ohm meter looking back at the switch with the motor off.
It should measure about 10,000 ohms +/- .
If to high it's in trouble.
If to low it's in trouble.
This normal resistance is built in to make this outside test determination.
.
If you replace the PCM, it requires reprogramming and two keys to complete the job.
The end result in dollars is high.
Thread Starter
|
Freshman User
Joined: Apr 2013
Posts: 32
Likes: 0
When the truck is running good and I check with test light at the Connector it Pulses when it it missfireing the test light is solid no pulsing.
To check with ohm meeter do I check it at the Connector or where the wires go into the Harness?
To check with ohm meeter do I check it at the Connector or where the wires go into the Harness?
Trending Topics
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
If the light is on solid that means a ground from the 'direction' of the PCM is present.
Seems like I answered this before.
Either the harness is rubbed through to a ground or the PCM switch goes shorted after it heats up.
This is the trouble you have to solve for.
The harness goes back to the PCM location just back of the battery area to the firewall.
If you can remove the PCM connector while the ground is present and the ground goes away, it's the PCM.
If not it's the harness.
Good luck.
Seems like I answered this before.
Either the harness is rubbed through to a ground or the PCM switch goes shorted after it heats up.
This is the trouble you have to solve for.
The harness goes back to the PCM location just back of the battery area to the firewall.
If you can remove the PCM connector while the ground is present and the ground goes away, it's the PCM.
If not it's the harness.
Good luck.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Thread Starter
|
Freshman User
Joined: Apr 2013
Posts: 32
Likes: 0
I know you probably been over this to but just want to clarify before I mess something up. When the ground is present. I need to remove the PCM Connector to see if the ground is still present. I need to clarify what is the PCM Connector. Be hind the battery on the firewall there is a bracket that holds what I would call the Harness. This box connects to anouther box that leads to the PCM. Its a farly big square Box that has Bunch wires coming out of it. next to it is a smaller box with wires That also leads to the PCM I believe. Will have to go look at it again when it get light. Is the Smaller one the PCM Connector? I am assuming it is. But just want to make sure.
THanks for your help and understanding....
THanks for your help and understanding....
Thread
Thread Starter
Forum
Replies
Last Post
1lrover1
2007 - 2014 Expedition & Navigator
25
Jul 2, 2022 07:39 PM