P2305 code 3.6L Done just about everything, any ideas? - JeepForum.com
 
LinkBack Thread Tools
post #1 of 6 Old 10-25-2021, 10:23 AM Thread Starter
cranbiz
Moderator
 
cranbiz's Avatar
2012 JK Wrangler 
 
Join Date: Nov 2015
Location: Wentworth
Posts: 5,336
P2305 code 3.6L Done just about everything, any ideas?

Ok, 2012 Sport 3.6. Heavily modified running a Superchips 87 Octane tune, which is basically a stock tune.

Started on the trail as a P0302, then a P2305 which I would expect with a P0302. Got it home, #2 coil was obviously bad.

Replaced coil. Within 20 miles, blew thru another coil. Got to where I was going for the weekend, pulled it apart, replaced coil. First 2 were OEM Mopar coils. This new one was a Duralast as I was in the middle of nowhere and lucky to get that one. Replaced the plugs at the same time even though the plugs only has 7K on them. Old (new) plugs were OEM Champions, new plugs were Iridium NGK's.

Start it up, sounds good, appears good, head up the mountain. Long story short, throws a P0302 code again with a P2305 and some funny transfer case shift high and other codes that didn't make sense and then the Jeep dies.

New coil burned and went shorted (all others went open) and takes the ASD fuse (again, in hind sight, makes sense.

A friend who knows a Mopar expert says it's got to be the PCM at this point so off it goes to Auto Computer Performance in FL. They find the driver circuit overheated and burned the board, which explains a lot of things. They clone my computer to a rebuilt one and send it back. Now all is well except that it's still throwing a P2305 code after it's hot and when it does, it is definitely missing.

I had ohmed out the cable, I have checked the pins at the coil, the connector mid harness and at the PCM. I have tightened the mates to the pins on the connections.

I'm at wits end here, what the heck is going on? The only thing I can guess now is a break in the coil ground wire from the PCM to the coil as the PCM completes the circuit by making the ground. If you look at this harness, it leaves the PCM and runs along the drivers side of the engine near the exhaust manifold, runs behind the engine at the back (and hard to get to), comes back up the passengers side next to the exhaust manifold up to a bracket over the #3 coil and then back behind the engine to the drivers side.

Whats my next step here. I have a thought but I don't want to color anyone's suggestions due to my frustration. New short harness is relatively cheap and easy, the main harness is OMG expensive and a royal PITA to change.

@jtec Do you have any ideas?

Anyone know it the length and resistance for the coil trigger wire matters?

Oh and BTW, I can now pull a 3.6L upper intake in about 8 minutes. Thinking about offering spark plug change service on 3.6's now to offset the cost of my Jeep.


02 WJ Laredo, heavily optioned but stock
12 JK, 3.5" Teraflex/Franken lift, Bilstein 5100's, BFG KM3's 37x12.5/R17
17 WK2 Trailhawk
KN4BBA
cranbiz is offline  
Sponsored Links
Advertisement
 
post #2 of 6 Old 10-25-2021, 11:51 AM
jtec
Registered User
 
jtec's Avatar
2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 10,624
maybe check the connector at coil, tight and corrosion free. Checl coil driver wire, open or shorted.
Plug s are gapped correctly?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
post #3 of 6 Old 10-25-2021, 01:48 PM Thread Starter
cranbiz
Moderator
 
cranbiz's Avatar
2012 JK Wrangler 
 
Join Date: Nov 2015
Location: Wentworth
Posts: 5,336
Quote:
Originally Posted by jtec View Post
maybe check the connector at coil, tight and corrosion free. Checl coil driver wire, open or shorted.
Plug s are gapped correctly?
Yes, plugs are gapped correctly. All connections from the PCM to the coil have been cleaned even though they all looked good and all female connector ends have been tightened up although they really were not loose. I also made sure that the male ends had not gotten pushed back into the housing.

You are confirming what my friends and I are thinking. That I have a break in the harness that is making connection when cold and separates when hot.

Seeing as the PCM is using the collapsing coil field as feedback on the trigger wire as an indication that combustion took place, can I just splice in a new wire that has close to the same resistance? My thought process is to splice one end at the PCM as close as possible to the connector, using the same gauge wire, keep it the same length and splice it in as close to the coil connector as possible. I was also thinking of having a connector in it like the factory, that would let me break the connection if necessary. I know it's not necessarily the right way but swapping out the inaccessable, $1500 harness that has more drops in it than the Winchester Mansion is not my idea of a weekend project.

Yes, my gut feeling is the break is in the $1500 harness section and not the $90 section simply because I can fairly easily swap out the $90 harness.

02 WJ Laredo, heavily optioned but stock
12 JK, 3.5" Teraflex/Franken lift, Bilstein 5100's, BFG KM3's 37x12.5/R17
17 WK2 Trailhawk
KN4BBA
cranbiz is offline  
 
post #4 of 6 Old 10-27-2021, 08:34 AM Thread Starter
cranbiz
Moderator
 
cranbiz's Avatar
2012 JK Wrangler 
 
Join Date: Nov 2015
Location: Wentworth
Posts: 5,336
Well, to close this out (hopefully) Last night I was able to do some detailed resistance measurements of the coil trigger wires in the harness. Cyl#2 was reading 6 ohms cold, Cyl#4 and $6 were reading 0.7 ohms. Broke the connection at the big grey connector and got 0.4 ohms for all 3 coils. So my suspicions appeared correct, there is some sort of issue in the expensive harness.

For now, I got a 16 GA THHN wire cut to the length (sort of) of the wire in the harness and spliced it into the PCM connector and the Coil connector. Ohmed it out and I now have 0.7 ohms on all 3 coil wires. Put it all back together and then drove it for about 40 minutes duplicating the conditions that would cause it to fail and all was fine.

02 WJ Laredo, heavily optioned but stock
12 JK, 3.5" Teraflex/Franken lift, Bilstein 5100's, BFG KM3's 37x12.5/R17
17 WK2 Trailhawk
KN4BBA
cranbiz is offline  
post #5 of 6 Old 10-27-2021, 02:37 PM
Bassman7365
Registered User
 
Join Date: Oct 2021
Posts: 5
I've been following your post and I think you've found it. Fingers crossed, as electronics can be quite maddening.
Bassman7365 is offline  
post #6 of 6 Old 10-27-2021, 03:31 PM Thread Starter
cranbiz
Moderator
 
cranbiz's Avatar
2012 JK Wrangler 
 
Join Date: Nov 2015
Location: Wentworth
Posts: 5,336
Quote:
Originally Posted by Bassman7365 View Post
I've been following your post and I think you've found it. Fingers crossed, as electronics can be quite maddening.
Yes, they can be. I have an electronics background and even I know when to send something to a specialist. When it got down to brass tacks, the harness was really the only thing left. Got a wheeling trip in a little over 2 weeks, going to run it a lot more to make sure.

02 WJ Laredo, heavily optioned but stock
12 JK, 3.5" Teraflex/Franken lift, Bilstein 5100's, BFG KM3's 37x12.5/R17
17 WK2 Trailhawk
KN4BBA
cranbiz is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome