[FIXED] Bank two miss

2008 GMC Acadia 3.6 runs for 30-45 minutes then goes to open loop with an obvious miss. P0300, P0202, P0204 and P0206 all trigger at the same time. The wiring diagram shows a ground on the side of bank two head that grounds the coils which in turn drives the injectors. The ground was corroded. I thoroughly cleaned with negative results. I’m lost. Been at this for three days. It was brought in for vvt intake cam solenoid which I cleaned and am now able to control with my Autel 908 pro. Stabilitrak service also lit. Swapped upstream sensors. Problem did not follow. Cleaned MAF as well as pcv valve and lines. 130k miles.

Hey Rm370! If possible, I'd suggest watching some scan data when this engine decides to start misfiring. RPM, MAF g/s, throttle position, all four O2's and short/long term trims on both banks. We need to get some direction on this misfire, and I'm hoping the O2's and trims will give us some.

I'd also suggest examining the Freeze Frame data if possible. GM normally has excellent Freeze Frame captures that can really help out in cases like this.

Which fault code did you start out with?

Currently the vehicle is not here. They are bringing it by this week. The initial codes were:

P0021 intake camshaft position system performance bank two
P0300 engine misfire detected
P0020 intake camshaft position actuator solenoid control circuit bank two
P0171 fuel trim system lean bank one
P0202 injector two control circuit
P0204 injector four control circuit
P0206 injector six control circuit.

Using my scanner I tested the VVT by advancing it in increments of 5°. All of them passed except for bank two intake cam actuator. Upon inspection it was dirty and slightly gummed up. That’s when I did the engine flush and completely cleaned the actuator. After installing it, I could run the active test and advance all of the camshafts accordingly.

The remaining remaining codes were:
P0300
P0202
P0204
P0206

It should be noted it took about 45 minutes of run time before the car would go into open loop and trigger the codes. I think I have mistakenly listed the injector codes incorrectly on my initial post. I will attempt to go back and edit that if that is the case. I will know for sure when I have the vehicle back and can run another scan.

I think I have mistakenly listed the injector codes incorrectly on my initial post. I will attempt to go back and edit that if that is the case.

No worries, I can go back and edit the opening post.

I will know for sure when I have the vehicle back and can run another scan.

Sweet! Let us know when you get the vehicle again.

When you do, I'd be interested to monitor the injector power feed when the misfire shows up. The power feeds for the injectors are broken up between two fuses. One for bank one, the other for bank two:



Since the injectors are beneath the intake, you can't monitor the voltage directly. BUT, X101 is out in the open and easy to access. See below:

Prior to seeing your last post, I was able to get the customer to drop the car off. I pulled it in the shop and it was running and idling just fine. I let it sit for about 10 minutes and then I grabbed the wiring harness next to the fuse box under the hood and pulled up on it and was able to get the engine to start missing. So the wiggle test proved there’s something wrong with the integrity of the wiring or a connection. I’m glad you pointed out X101 for me. That helps out a lot. I will try and hook up to both banks and get a voltage reading and compare the two when it starts to misfire. The customer purchased this car used two years ago. I did notice the bracket under the fuse box was broken and the wiring harness is not routed correctly. It was kind of just laying all over the place. I was able to repair the bracket but I still suggested to the customer to try and get a used fuse box and engine wiring harness if he can. My gut tells me there was somebody in here trying to diagnose this previously. I also noticed wire ties holding the connections to the computer. A real hack job. Thank you very much for your quick response.

I have an excellent video showing the miss with a wiggle test. It is 20 seconds long but won’t load. Too big I guess. I shot it with my IPhone.

Prior to seeing your last post, I was able to get the customer to drop the car off. I pulled it in the shop and it was running and idling just fine. I let it sit for about 10 minutes and then I grabbed the wiring harness next to the fuse box under the hood and pulled up on it and was able to get the engine to start missing. So the wiggle test proved there’s something wrong with the integrity of the wiring or a connection.

Very nice. Definitely on the right track.

I did notice the bracket under the fuse box was broken and the wiring harness is not routed correctly. It was kind of just laying all over the place. I was able to repair the bracket but I still suggested to the customer to try and get a used fuse box and engine wiring harness if he can.

Sounds like the fuse box may have been disassembled previously. That by itself isn't surprising, since most techs I know (including me) disassemble the box to allow the engine harness to come out with the powertrain during timing chain service.

It may be worth getting the fuse box out and in your hands to inspect for corrosion/spread pins/burnt contacts on the box AND the bulk connectors beneath.

Excellent idea! I will do it first thing in the morning. Thanks!

I did strip the covering from the harness in that area and found nothing that jumped out. There were way too many wires to do voltage drop tests/wiggle tests on each one individually. I never thought to pull the entire box and inspect it. I will certainly report back even if I find the culprit. I am a very appreciative person. Thanks again for the guidance.

The owner is picking up a used engine wire harness tomorrow night ($265!!) ouch! I got tied up on suspension work today and some waaaay overdue shop cleaning. I did not get a chance to pull the fuse box. Thought I would tackle it after he drops off the parts.

The owner is picking up a used engine wire harness tomorrow night ($265!!) ouch! I got tied up on suspension work today and some waaaay overdue shop cleaning. I did not get a chance to pull the fuse box. Thought I would tackle it after he drops off the parts.

No worries. Let us know what you find!

I pulled the fuse box and inspected as much as I could and nothing look burnt or abnormal. I also started pulling the wiring harness and it’s ready to come out however I would like to wait until I have the other one so I can replace it as I take the old one out. Just for routing purposes. Hoping he drops it off tomorrow. The salvage yard did not have it ready for him when he went to pick it up. I have the maxi scope with my Autel 908 scanner but I do not know how to quite use it yet. Still trying to figure that one out.

I installed the salvage yard wiring harness and fuse box. I have the car through two 20 minute heating and cooling cycles. No codes or malfunctions as of yet. The question is, how many times do I run it before returning the vehicle to the customer? The last time it took over one hour of driving before it threw the code. I plan on driving it tomorrow maybe for a 10 mile round trip or more. I might do that once or twice. Fingers crossed I guess.

I hate to be a parts changer. I commonly referred to it as parts darts. You keep throwing parts until you hit the bull’s-eye. In this case it was different. The harness and the fuse box were so butchered from previous attempts to repair or whatever that I felt it necessary to replace before going further with diagnosis. I hope that makes sense. I simply hate not knowing what the exact cause was for the problem.

I am going to call this one fixed. I ran the car through four heat cycles and everything is working as it should. Thank you for your assistance. I wish I could tell you what the exact problem was but I simply could not pinpoint it.

I wish I could tell you what the exact problem was but I simply could not pinpoint it.

Don't sweat it!

I would not call this 'parts darts' at all. You knew to a certainty there was a problem in the harness or the fuse box. Sure, you could have narrowed it down further. But what if you got down to an internal connection in the fuse box itself? Plus, you don't know what other kind of monkey business the wiring has been through.

I have no problem with the way this one got repaired. Playing parts darts would have been six injectors, an alternator and a PCM.

Rm370 wrote:

I am going to call this one fixed. I ran the car through four heat cycles and everything is working as it should. Thank you for your assistance. I wish I could tell you what the exact problem was but I simply could not pinpoint it.

As Tyler said, don't sweat it..... Your approach looks reasonable to me ☺️, some times we're efficient and other times we're effective only.