2003 Liberty 3.7L sport, Reman engine from Tri-Star, p0304 code

[Ksat]

PleasHas anyone ever created a "bypass circuit" directly from the PCM to a particular coil/injector? The thought is that if a bypass is possible, and I can run wires to the coil/injector on cyl 4, that would either confirm/refute whether there is a short buried in the harness somewhere.e elaborate on your "things get hot" experience, that may be significant here.

I just mean when the engine got up to temperature, a bad connection in a wire going to a fuel injector got worse and the injector stopped working. When things cooled down, the resistance in the wire lessened and it started working again.

Has anyone ever created a "bypass circuit" directly from the PCM to a particular coil/injector? The thought is that if a bypass is possible, and I can run wires to the coil/injector on cyl 4, that would either confirm/refute whether there is a short buried in the harness somewhere.

Have you tried noting the color of the wires that terminate at the coil and injector then looking for those same ones coming out of the PCM?

The scanner only shows that the cyclinder misfire count has reached some threshold. Any recommendation on buying a better scanner without breaking the bank?

A scanner that advertises it can read mode 6 data would fit the bill there. I wouldn't worry too much about running out and getting a new scanner right now, though, as I doubt it would aid much in your diagnoses in your particular case.

 

[MarkG]

Checking the ignition and injection connectors for cracks, debris; or corrosion ?

 

[dtennes]

I just mean when the engine got up to temperature, a bad connection in a wire going to a fuel injector got worse and the injector stopped working. When things cooled down, the resistance in the wire lessened and it started working again.



Have you tried noting the color of the wires that terminate at the coil and injector then looking for those same ones coming out of the PCM?



A scanner that advertises it can read mode 6 data would fit the bill there. I wouldn't worry too much about running out and getting a new scanner right now, though, as I doubt it would aid much in your diagnoses in your particular case.

@Ksat, thank you for the response and your thoughts are excellent.

Yes, I've tracked the color coding as far I as I could without starting to really unwrap the harness, which is really showing age. I want to avoid pulling it apart until I can find someone who understands the physical geography of the "F" circuit (from the diagrams in the "8W" sections of the 2003 KJ Repair Manual). The fear is that some other weird wire in the loom will crumble and I create a larger rewiring problem.

What I want to do is (a) cut the wires between the Power Distro Center and the coil (which is 14 gauge) and then (b) again between the coil and the PCM (which is also 14 gauge), (c) splicing in a new complimentary pair of wires that remain outside of the harness and rerouted along the firewall in a separate protective jacket. The plan includes doing the same thing for the injector, which sort of follows the same routes as the coil wire. This would constitute the "bypass" I am imagining,

Regarding thoughts on the "scanner", the KJ has been back to the shop a couple of times and after a few q&a sessions, the impression is that I need to get the diag report from shop #1, then take the KJ to another shop (shop #2, tbd) and pay for another round of diagnostics. A new set of eyes, with hopefully a longer track record with Jeep-specific vehicles can then compare and contrast reports and maybe experience will prevail.

Regarding temp. I've been reading up on signal degradation and what causes it, and I totally get your notes on temp and increasing resistance. The ignition harness is pretty close to the block, and the suspicion is that the worn state of the existing harness is combining with radiant heat... which is the basis for my interest in creating that bypass away from the block.

 

[dtennes]

Checking the ignition and injection connectors for cracks, debris; or corrosion ?

@MarkG thank you for the response.
I've been climbing all over the place tracking wires and their physical status. The isulation looks and feels old (sort of rough on the outside but I'm hoping its just 20 years of road dust), but it's still intact. Paid close attention to the insertion points on the connectors and they all look good. The shop ran basic electrical forensics, looking for shorts and that doesn't exist...

The connectors on the coil and the injector have been replaced by the shop. I checked the splices and they look solid.

 

[DadOSix]

Don’t forget the old Duramax fuel injector trick -

The 6.6 engines were notorious for cyl 3 and 7 setting codes for misfiring. No actual defect in the injector could be found. But —- thinking about what you said time-wise, it makes me wonder if the connection pin at the injector is heating up and increasing resistance and making the Miss code. We used to pull the pin from the plug, and ‘tighten it up’ a bit with a slight crush from needle nose pliers. Put back in the plug and the miss ‘mysteroiusly’ was no more.

 

[derekj]

Has anyone ever created a "bypass circuit" directly from the PCM to a particular coil/injector? The thought is that if a bypass is possible, and I can run wires to the coil/injector on cyl 4, that would either confirm/refute whether there is a short buried in the harness somewhere.

I would rather not speculatively tear apart the ignition harness if it can be avoided.

I ran new wires from the drivers side coils to the ecm when I got my Liberty. The previous owner had problems with the computer so I wanted to make sure the new computer I put in wasn't going to get damaged by a bad wire.

 

[yrvmrv98]

I had the same issue with my 2005 Liberty with 140000 miles. I figured out over the last 2 years when I do the oil filter change I ALWAYS add about an 1/8 more oil than the safe line on my dipstick. For the last 2-3 years I would get a #2 cylinder misfire but it could never be replicated in the shop. Since I always add more oil than the safe line I have NEVER again gotten a P0304 code indicating # 2 cylinder misfire. I now have 165000 miles. And she runs like a champ. hoping for another 40-50000 miles.
Very strange, hoping this helps.

 

[dtennes]

I had the same issue with my 2005 Liberty with 140000 miles. I figured out over the last 2 years when I do the oil filter change I ALWAYS add about an 1/8 more oil than the safe line on my dipstick. For the last 2-3 years I would get a #2 cylinder misfire but it could never be replicated in the shop. Since I always add more oil than the safe line I have NEVER again gotten a P0304 code indicating # 2 cylinder misfire. I now have 165000 miles. And she runs like a champ. hoping for another 40-50000 miles.
Very strange, hoping this helps.

@yrvmrv98, hello and thanks for the suggestion... I normally let the Oil Shops handle fluids (too much hassle with disposable toxics) but I know what they use, so having an extra bottle in the garage is np.

 

[dtennes]

I ran new wires from the drivers side coils to the ecm when I got my Liberty. The previous owner had problems with the computer so I wanted to make sure the new computer I put in wasn't going to get damaged by a bad wire.

@derekj, a couple of clarification questions:
1. Was your Liberty actually throwing p03xx code(s) before you rewired the drivers side?
2. When you rewired, did you
(a) actually run 3 pairs of coil wires from the coils all the way back to the PCM (what I am imagining to be a true "bypass"), or

(b) simply buy new ignition coil connectors (example Standard Connector "S-2087") and splice the whips of those connectors into the harness wires at the block?

Your help is really appreciated.

 

[dtennes]

To everyone:

I cannot begin to describe how cool, and helpful, the Forum members have been. You have my promise that I will put together a complete walk thru of this work and had it over to the moderators to park it wherever they think will benefit everyone in the future.

The more I get to know the workings of this 2003 Liberty (which I originally ordered from Jeep), it really is a rather elegant design. The only thing that's frustrating are the wiring harnesses which some genius decided to wrap around the block like an octopus. They should have added a couple of inches in wire length here and there, and stood the harness off of the hot parts a bit.

 

[dtennes]

"Missing Ignition capacitor"
Apparently there is supposed to be one of these installed (see capacitor_b1 photo) on the left engine compartment firewall (see cpacitor_b2 photo) according to the manual (see capacitor_b3 photo).

The point of a capacitor (I'm no electrician but I can understand definitions/explanations) is to provide a stable charge delivery of _____ amps at the expected level of voltage.

There's a reason why these things get included in a circuit, and mine seems to be missing from the engine compartment. The hypothesis is that a mechanic ended up with a loose cable/connector, couldn't figure out where it went, and "since the engine seemed to be running fine at the time, we'll just cut it off and forget about it".

If that hypothesis is truth, then the new/replacement capacitor needs to be screwed into the firewall where it belongs... but I have no idea where to splice in the connector whip. The anticipation is that it is a single-wire splice because there is only one connector pin exposed in the connector socket on this part.

UPDATE TO THIS PARTICULAR THREAD REGARDING "IGNITION CAPACITOR"
1. I went over the 2003 KJ Jeep Repair Manual in detail.
2. There is some amount of vague explanation *and* diagramming in multiple locations in the Manual regarding the maint of a 2.4L inline 4 cylinder... and the 3.7L V6.
3. I also spent two afternoons climbing all over 5 different 2003 Liberty V6s in 2 different salvage yards, tracing the PCM and TCM wire harnesses.
4. None of those 3.7L 2003s had an ignition capacitor attached to either the firewall or the wire harness channel, and there was no rogue wire/connector hanging off of perfectly intact harnesses the the vicinity of where such a capacitor is supposed to be located.
5. The conclusion is that said capacitor does not exist in the 2003 V6 Liberty models, but it is noted in the Repair Manual, so the anticipation is that this Ignition Capacitor is only required for the 2.4L coils. Note that the coil design for the 4 cylinder is definitely different from that of the V6... so the suspicion of a special-purpose component specifically for the 2.4L is very strong.
6. I could not confirm the location of this Ignition Capacitor for 2.4L inline 2003 Libertys, because there weren't any in the yards. However, I was only concentrating on 2003s, and there were some 2004s and 2005s out there so I will look further next trip out.

 

[dtennes]

>>>>>>> THIS IS A WORK IN PROGRESS <<<<<<<
>>>>>>> DO NOT USE UNTIL I REMOVE THIS WARNING HEADER <<<<<<<<<
>>>>>>> BECAUSE I CONTINUE TO FIND MORE EFFECTIVE/EFFICIENT/ELEGANT TACTICS FOR THE VARIOUS STEPS AS I PROCEED<<<
>>>>>>> I WILL EDIT THE ATTACHED PART1.txt and PART2.txt FILES UNTIL THE FINAL DRAFT IS DONE <<<<<<<<

Subject: PART 1: Creating ignition coil and fuel injector bypass circuits for a 2003 3.7L Liberty Sport. Content covers circuits F142 (PDC to Fuel Injectors) and A142 (PDC to Ignition coils)

I've discovered that there is a 10K limit on posting size (ha), so I am now putting everything into attachments. For the circuitry that goes from the Power Distro Center to each of the Fuel injectors and Ignition Coils, see the attached file "PART 1.txt"

 

[dtennes]

The 2003 Liberty factory manual (8w wiring schematics) should identify the circuit. see link below.
http://www.colorado4wheel.com/manuals/Jeep/KJ/2003JeepKJServiceManual.pdf

Hi LibertyTC- I'm in the process of assembling a How To guide for creating a simple custom plug-in harness to bypass the original circuitry for the ignition coils and fuel injectors for 2002-2003 (and possibly later models) of 3.7L KJs. Is that the kind of thing that should get parked out under "Resources", or is it better just left in place (and let the search engine surface the content)? I ask because the plan is to include diagrams and photos, and I don't know if there's a limit on file sizes embedded in regular message feeds. Please advise, thanks.

 

[DadOSix]

Subject: PART 1: Creating ignition coil and fuel injector bypass circuits for a 2003 3.7L Liberty Sport. Content covers circuits F142 (PDC to Fuel Injectors) and A142 (PDC to Ignition coils)

If you are getting rogue/intermittent/sporadic/etc p03xx "Cylinder Misfire" codes (like I am), this may help you to isolate a problem with damaged wires. The misfire may actually be caused by a variety of things like bad sensors, fuel delivery problems, dying catalytic converters, or other problems... but I had every other one of those possibilities investigated and eliminated. The only thing left for me to investigate is the physical circuitry... if that doesn't do it then all that's left is a badly remanufactured engine.

Creating isolated circuits to bypass/replace existing ignition coil wiring, and fuel injector wiring is possible with a minimal amount of work.

Note 1: This is PART 1 of two parts. PART 1 only covers the circuitry that originates from the PDC (Power Distro Center) and terminates at the corresponding injectors and coils. PART 2 (in progress) will cover the other side of the bypass solution which originates at the PCM (Powertrain Control Module) and terminates that the corresponding injectors and coils.

Note 2: Today is 2023-Sep-8. The following is a ***Work in Progress***, so please don't take any of this as gospel until I post content with the label *Final Version*. Also, please consider this a collaborative effort so any/all input/corrections/clarifications/etc is greatly appreciated.

Note 3: Apparently the Service Manual was compiled without the benefit of either quality control or a managing editor, because there are omissions and flat out misinformation, and my goal is to spare you a lot of ratholes. I will do my best to clarify and if anyone has questions, let me know and I will help as best as I can.

Note 4: This should also work for 2002 (99% confident) and 2004 3.7L (90% confident, if someone shares the Service Manual for the 2004 I will know for sure). I do not think the type of transmission (auto/manual/4WD/2WD) makes any difference.

Note 5: The final version of this will hopefully include detailed photos, explicit manual references, vendor resources, and whatever else I can think of to smoth the path forward.

Note 6: Don't be a hack. Carelessness will leave you with a dead KJ and you'll probably have to start the whole thing over from scratch.
6.1: Use either SXL or TXL (what I'm using) wire of the correct gauge.
6.2: Make sure your connectors are weather-proof (iow, little rubber collars around the wires where they insert into the connector body).
6.3: You are running new wire anyway, so buy some decent new heat resistant tubing to protect your work.
6.4 Use Tesa harness tape #51036 for wire management and to seal the protective tubing to the connectors.

Background: For research purposes. I went to a salvage yard and carefully pulled the entire engine compartment main-trunk wiring harness (that fat black snake that wraps around the back of the engine block right below the intake manifold. This trunk line includes the following branches...
1. Bank 1 of the PCM, which is the source for the signals to 5 coils
2. Bank 2 of the PCM
3. The entire branch that goes off to the TCM
..which you do not have to do, the point is that the research is based on first-hand mechanical forensics. I have no intention of cannibalizing wiring components. This is a custom bypass exercise.

Ultimately you will need to locate the following two large 10-way connectors (using the Service Manual IDs) which are the root of two 6-way splices that complete the two circuits in focus, fuel injectors and ignition coils.

Fuel injectors from PDC, Service manual pages 8W-10-20, and 8W-80-18.
Ignition coils from PDC, pages 8W-10-21, and 8W-80-24.

As you read the following, understand that there are 4 different perspectives when considering a connector, and that a connector consists of two halves that you couple together, a male half and a female half. Yeh, you know all about this, but you don't know what a mess the Service Manual diagrams and instructions are, so I am spelling this out.
1. Male half face, this is the side of male connector half that has male pins sticking out of it
2. Male half terminals, this is the other side of the male half, opposite the male pins, where the wires go into this half.
3. Female half face, this is the side of the female half that the male half plugs into, and it has sockets for the male pins.
4. Female half terminals, this is the other side of the female half, opposite the female sockets, where the wires go into this half.

PCM side of the Fuel injector circuit:
"C103", which is in line in the F142 circuit. Location is (from driver position) right rear of engine compartment, either near or attached to the firewall. It is a 10-pin rectangular connector, 2 rows of 5 pins each.
(A) You need to isolate a single 18 gauge wire, that is insulated with an orange/dark-green color, no other wire is this color, according to the Service Manual that wire is located in connector position "1" ***of the female half of this connector***.
(B) So, leave yourself about 6-8" of whip hanging out of the female half and cut there.
(C) At this point you have now severed the 6 wires that lead to the orange/dark-green inputs on all fuel injector 2-way connectors.
(D) Lay out 6 new replacement 18 gauge wires cut to efficient lengths to reach the 6 injectors from the 10-way female connector
(E) Take 1 more 8" long piece of 18 gauge wire and splice all 6 of the branches together with this stub
(F) Splice the stub to the original 18 gauge whip that's still hanging off the female half of the 10-pin connector
(G) Splice the 6 bare ends, to each of 6 new 2-way injector connectors (recommended: Standard part #S-824) using the connector lead designated to go to the PCM. This is a Female connector half only.


PCM side of the Ignition Coil circuit:
"C112", which is in line in the A142 circuit. Location is (from driver position) left rear of engine compartment, either near or attached to the firewall. It is another (identical in appearance) 10-pin rectangular connector, 2 rows of 5 pins each.
(A) You need to isolate a single 14 gauge wire...

>>>pay attention, that's a 14 gauge wire<<<
You must use 14 gauge because anything else will have a different resistance, which can contribute to the PCM misinterpreting whether a cylinder has successfully fired. A smaller gauge can have the same effect as using cheapo wire that is not heat tolerant, or having damaged insulation, or having deteriorated stranded core.

...that is insulated with (coincidentally) an orange/dark-green color (but this one is thicker than the wires for the injectors), no other wire is this color, according to the Service Manual that wire is located in connector position "10" ***of the female half of this connector***.
(B) So, once again leave yourself about 6-8" of whip hanging out of the female half and cut there.
(C) At this point you have now severed the 6 wires that lead to the orange/dark-green inputs on all downstream ignition coil connectors.
(D) Lay out 6 new replacement 14 gauge wires cut to efficient lengths to reach the 6 ignition coils from the 10-way female connector
(E) Take 1 more 8" long piece of 14 gauge wire and splice all 6 of the branches together with this stub
(F) Splice the stub to the original 14 gauge whip that's still hanging off the female half of the 10-pin A142 circuit connector
(G.1) Splice the 6 bare ends, to each of 6 new 14 gauge socket bare ends that came with the connector kits. Recommended: Standard part #S-2087, which is a kit that you must assemble. This is a Female connector half only.
(G.2) What is important about this recommendation is that this kit comes with the connector body plus 6 individual terminal whips, three of which are 14 gauge and 3 are 16 gauge.
(G.3) ***USE THE 14 GAUGE***. In fact throw out the 16 gauge the minute you open the package so you don't accidentally use the wrong gauge.
(G.4) The ignition coil connector body has 3 empty cavities out the back. You will insert your spliced socket connectors, one per connector, into the middle cavity of each of the 6 connectors. Make sure the rubber collar is snug, be careful not to damage the insulation on the wire.

At this point all of your Power Distro Center side of the wiring is done. Part 2 will cover the PCM side.

damn fine write up!

 

[derekj]

@derekj, a couple of clarification questions:
1. Was your Liberty actually throwing p03xx code(s) before you rewired the drivers side?
2. When you rewired, did you
(a) actually run 3 pairs of coil wires from the coils all the way back to the PCM (what I am imagining to be a true "bypass"), or

(b) simply buy new ignition coil connectors (example Standard Connector "S-2087") and splice the whips of those connectors into the harness wires at the block?

Your help is really appreciated.

When I got my truck it had codes for the coil driver circuits to all three coils on the drivers side of the engine (can't remember the exact codes). The PO originally had one bad coil driver on the drivers side and replaced the computer with a reman unit. Then he had the three coil driver codes(ended up being a bad reman computer), he threw a bunch of parts at it, but couldn't fix it so he gave up and that's when I bought it. Just to be safe I load tested all the coil wiring and after some more diagnosing determined the computer was bad. Just to be safe I ran new wires from the coils back to the ecm. I only ran one wire back as the other wire at the coil is the 12 volt ignition feed to the coil and I knew that circuit was ok because the rest of the coils were good. I did not replace the connectors at the coils.

 

[dtennes]

Subject: PART 1: Creating ignition coil and fuel injector bypass circuits for a 2003 3.7L Liberty Sport. Content covers circuits F142 (PDC to Fuel Injectors) and A142 (PDC to Ignition coils)

If you are getting rogue/intermittent/sporadic/etc p03xx "Cylinder Misfire" codes (like I am), this may help you to isolate a problem with damaged wires. The misfire may actually be caused by a variety of things like bad sensors, fuel delivery problems, dying catalytic converters, or other problems... but I had every other one of those possibilities investigated and eliminated. The only thing left for me to investigate is the physical circuitry... if that doesn't do it then all that's left is a badly remanufactured engine.

Creating isolated circuits to bypass/replace existing ignition coil wiring, and fuel injector wiring is possible with a minimal amount of work.

Note 1: This is PART 1 of two parts. PART 1 only covers the circuitry that originates from the PDC (Power Distro Center) and terminates at the corresponding injectors and coils. PART 2 (in progress) will cover the other side of the bypass solution which originates at the PCM (Powertrain Control Module) and terminates that the corresponding injectors and coils.

Note 2: Today is 2023-Sep-8. The following is a ***Work in Progress***, so please don't take any of this as gospel until I post content with the label *Final Version*. Also, please consider this a collaborative effort so any/all input/corrections/clarifications/etc is greatly appreciated.

Note 3: Apparently the Service Manual was compiled without the benefit of either quality control or a managing editor, because there are omissions and flat out misinformation, and my goal is to spare you a lot of ratholes. I will do my best to clarify and if anyone has questions, let me know and I will help as best as I can.

Note 4: This should also work for 2002 (99% confident) and 2004 3.7L (90% confident, if someone shares the Service Manual for the 2004 I will know for sure). I do not think the type of transmission (auto/manual/4WD/2WD) makes any difference.

Note 5: The final version of this will hopefully include detailed photos, explicit manual references, vendor resources, and whatever else I can think of to smoth the path forward.

Note 6: Don't be a hack. Carelessness will leave you with a dead KJ and you'll probably have to start the whole thing over from scratch.
6.1: Use either SXL or TXL (what I'm using) wire of the correct gauge.
6.2: Make sure your connectors are weather-proof (iow, little rubber collars around the wires where they insert into the connector body).
6.3: You are running new wire anyway, so buy some decent new heat resistant tubing to protect your work.
6.4 Use Tesa harness tape #51036 for wire management and to seal the protective tubing to the connectors.

Background: For research purposes. I went to a salvage yard and carefully pulled the entire engine compartment main-trunk wiring harness (that fat black snake that wraps around the back of the engine block right below the intake manifold. This trunk line includes the following branches...
1. Bank 1 of the PCM, which is the source for the signals to 5 coils
2. Bank 2 of the PCM
3. The entire branch that goes off to the TCM
..which you do not have to do, the point is that the research is based on first-hand mechanical forensics. I have no intention of cannibalizing wiring components. This is a custom bypass exercise.

Ultimately you will need to locate the following two large 10-way connectors (using the Service Manual IDs) which are the root of two 6-way splices that complete the two circuits in focus, fuel injectors and ignition coils.

Fuel injectors from PDC, Service manual pages 8W-10-20, and 8W-80-18.
Ignition coils from PDC, pages 8W-10-21, and 8W-80-24.

As you read the following, understand that there are 4 different perspectives when considering a connector, and that a connector consists of two halves that you couple together, a male half and a female half. Yeh, you know all about this, but you don't know what a mess the Service Manual diagrams and instructions are, so I am spelling this out.
1. Male half face, this is the side of male connector half that has male pins sticking out of it
2. Male half terminals, this is the other side of the male half, opposite the male pins, where the wires go into this half.
3. Female half face, this is the side of the female half that the male half plugs into, and it has sockets for the male pins.
4. Female half terminals, this is the other side of the female half, opposite the female sockets, where the wires go into this half.

PCM side of the Fuel injector circuit:
"C103", which is in line in the F142 circuit. Location is (from driver position) right rear of engine compartment, either near or attached to the firewall. It is a 10-pin rectangular connector, 2 rows of 5 pins each.
(A) You need to isolate a single 18 gauge wire, that is insulated with an orange/dark-green color, no other wire is this color, according to the Service Manual that wire is located in connector position "1" ***of the female half of this connector***.
(B) So, leave yourself about 6-8" of whip hanging out of the female half and cut there.
(C) At this point you have now severed the 6 wires that lead to the orange/dark-green inputs on all fuel injector 2-way connectors.
(D) Lay out 6 new replacement 18 gauge wires cut to efficient lengths to reach the 6 injectors from the 10-way female connector
(E) Take 1 more 8" long piece of 18 gauge wire and splice all 6 of the branches together with this stub
(F) Splice the stub to the original 18 gauge whip that's still hanging off the female half of the 10-pin connector
(G) Splice the 6 bare ends, to each of 6 new 2-way injector connectors (recommended: Standard part #S-824) using the connector lead designated to go to the PCM. This is a Female connector half only.


PCM side of the Ignition Coil circuit:
"C112", which is in line in the A142 circuit. Location is (from driver position) left rear of engine compartment, either near or attached to the firewall. It is another (identical in appearance) 10-pin rectangular connector, 2 rows of 5 pins each.
(A) You need to isolate a single 14 gauge wire...

>>>pay attention, that's a 14 gauge wire<<<
You must use 14 gauge because anything else will have a different resistance, which can contribute to the PCM misinterpreting whether a cylinder has successfully fired. A smaller gauge can have the same effect as using cheapo wire that is not heat tolerant, or having damaged insulation, or having deteriorated stranded core.

...that is insulated with (coincidentally) an orange/dark-green color (but this one is thicker than the wires for the injectors), no other wire is this color, according to the Service Manual that wire is located in connector position "10" ***of the female half of this connector***.
(B) So, once again leave yourself about 6-8" of whip hanging out of the female half and cut there.
(C) At this point you have now severed the 6 wires that lead to the orange/dark-green inputs on all downstream ignition coil connectors.
(D) Lay out 6 new replacement 14 gauge wires cut to efficient lengths to reach the 6 ignition coils from the 10-way female connector
(E) Take 1 more 8" long piece of 14 gauge wire and splice all 6 of the branches together with this stub
(F) Splice the stub to the original 14 gauge whip that's still hanging off the female half of the 10-pin A142 circuit connector
(G.1) Splice the 6 bare ends, to each of 6 new 14 gauge socket bare ends that came with the connector kits. Recommended: Standard part #S-2087, which is a kit that you must assemble. This is a Female connector half only.
(G.2) What is important about this recommendation is that this kit comes with the connector body plus 6 individual terminal whips, three of which are 14 gauge and 3 are 16 gauge.
(G.3) ***USE THE 14 GAUGE***. In fact throw out the 16 gauge the minute you open the package so you don't accidentally use the wrong gauge.
(G.4) The ignition coil connector body has 3 empty cavities out the back. You will insert your spliced socket connectors, one per connector, into the middle cavity of each of the 6 connectors. Make sure the rubber collar is snug, be careful not to damage the insulation on the wire.

At this point all of your Power Distro Center side of the wiring is done. Part 2 will cover the PC

I had the same issue with my 2005 Liberty with 140000 miles. I figured out over the last 2 years when I do the oil filter change I ALWAYS add about an 1/8 more oil than the safe line on my dipstick. For the last 2-3 years I would get a #2 cylinder misfire but it could never be replicated in the shop. Since I always add more oil than the safe line I have NEVER again gotten a P0304 code indicating # 2 cylinder misfire. I now have 165000 miles. And she runs like a champ. hoping for another 40-50000 miles.
Very strange, hoping this helps.

Did you, or some shop mechanic, ever replace the connector for either the Ignition Coil or the Fuel Injector on cyl #2 ?

 

[dtennes]

When I got my truck it had codes for the coil driver circuits to all three coils on the drivers side of the engine (can't remember the exact codes). The PO originally had one bad coil driver on the drivers side and replaced the computer with a reman unit. Then he had the three coil driver codes(ended up being a bad reman computer), he threw a bunch of parts at it, but couldn't fix it so he gave up and that's when I bought it. Just to be safe I load tested all the coil wiring and after some more diagnosing determined the computer was bad. Just to be safe I ran new wires from the coils back to the ecm. I only ran one wire back as the other wire at the coil is the 12 volt ignition feed to the coil and I knew that circuit was ok because the rest of the coils were good. I did not replace the connectors at the coils.

Thank you, this is very reassuring. Did you simply cut off the wires coming out of the ECM and the coil connector, and then splice new wires in between, or did you pull the terminals out of the connector and the corresponding ECM terminal cavities? How long ago did you do this, and are those codes gone for good? Please share your thoughts.

 

[derekj]

Thank you, this is very reassuring. Did you simply cut off the wires coming out of the ECM and the coil connector, and then splice new wires in between, or did you pull the terminals out of the connector and the corresponding ECM terminal cavities? How long ago did you do this, and are those codes gone for good? Please share your thoughts.

I just cut close to the connectors and spliced - did the repairs in October last year and have had no problems since.

 

[dtennes]

I just cut close to the connectors and spliced - did the repairs in October last year and have had no problems since.

Outstanding! I have been worrying about whether or not to use splices because I've read about the effects of increased resistance. After discussions with various mechanics (and a Flagship1 ECU/PCM tech), my understanding is that when a coil fires some sort of "pulse"/"voltage change"/"other phenom" gets detected by the PCM, and as those detections/sec cross some threshold count a p03xx code gets thrown. My concern was that increased resistance would impact that detection.

I was planning on doing the splice attempt 1st anyway, and watching the results... with a fallback plan to pull the pins from the PCM and the 10-way connectors that complete the circuit and reinsert new ones attached to unspliced wires.

But, if you did a splice a year ago and have had no problems... I think you have proved the best and easiest bypass tactic.

 

[DadOSix]

Just my opinion:

I would try to source new pins and do the whole Circuit end to end.

It needs a special pin tool to get them out and fairly easy to reinsert.

For just the reasons you said - resistance issues. If a pin gets loose, spread, or green and crusty, the issue will persist.

But then again, I tend to go the extreme when trying to get it fixed.