p0201 and p0301

[BigEagle]

Well, it all started last year with the Envoy running rough and missing badly. Took it to dealership and $800 later all ran nicely, for a year. Now has same/similar problem just nat as bad- yet. After searching around and finding some very good tips (May03LT) , I did some troubleshooting. I had codes p0301 and p0201, ok, and p0300. So I swapped coils 1 and 3 and also swapped plugs 1 and 2, cleared the codes and ran for a test. The truck threw the same codes. The p0201 said injector ckt open so I did some wire tracing. After finding the fuel injector harness, I checked the ohms and they were good. Also checked for continuety and grounds on the fuel injector harness and back the other way all the way to the PCM using the harness pinouts I found. And all is good. (continuety was good and there was no crossing of wires as in a harness melting together.) Then I pulled the intake to get to the injectors.. Man!!!!! my fingers now have eyeballs.

The injectors looked OK, but the wiring loom looked like it was chewed on by critters -- no nicks on the wires and continuety was good with non cross shorted. The injectors looked OK but the plastic ends where the fuel sprays were crooked and uneven on all. I decided to replace all injectors since they were hard to get to instead of just swapping the number 1 with another one-- they should be here by Tuesday.. Maybe, all lots of snow up north. Mostly sunny here in Florida.

In the pics attached I found some oil residue in the intake runners and in the head intake ports but no oil between the head and block or the head and valve cover. Where is it coming from?? Valve stems leaking, piston blowby, EGR recirc, gremlins feed after midnight??

It uses very little oil (1/2 qt over 5000 miles), was running decently until this current problem, about 17-19 mpg's.

Anybody have any ideas??

Argh!!! can't find the spell check.

 

[IllogicTC]

I think you have the codes figured out. P0201, Injector Circuit Open, which could of course make the 0301 come up.

The oil? Seems normal enough. The PCV is too simplistic, no valve that I can remember. Just a route to get it sucked out and burnt up. It can bring oil with it of course, this is part of the reason part of our recommended maintenance here is to clean the (back side) of the throttle body plate, as it gets gummed just like that, too.

 

[BigEagle]

I found the oil curious. Probably not a head gasket because it was not just between two specific cylinders. If the injectors don't fix the problem then maybe the PCM or camshaft position sensor or ..........well one thing at a time. I hope I remember where all those bolts go.

If all else fails then I think a duramax might squeeze in there.

 

[BlazingTrails]

It is normal to find oil build up in the intake and ports. it just build up over time and all you have to do is clean it out. it is not a sign of a blown head gasket.

 

[BigEagle]

So I received the injectors by mail from Amazon. Can't believe they were only $25 each instead of $150 each from Gordon Chevy Orange Park, fl . What a deal. At the Zone and Adanced were around $50-$60 each. So Church and volunteering at food bank and work, I finally have chance to work on truck- woops, forgot the dentist!!. Dang!! Now its raining. Up north folks would call this a blizzard.

About 2 feet of "snow" on ground already.

maybe wednesday I can start assemby and have it done by Thanksgiving. The wiring harness is tested and doctored up and intake and TB cleaned--now just waiting for break in weather and free time.

The dog wants to go for a ride!!

The boys at Fort Clinch. Look it up.

Liquid Sunshine/Snow!!!!

And a beautiful stormy winter in Florida.

 

[BigEagle]

I put it all together before Thanksgiving Dinner and running. Good news is I put it together and it runs!!! Bad news is that it still throws the p0201 code. It runs just slightly rough (with an obvious miss.) I pulled the number one coil harness plug while running and it ran the same. So, whats left??? the wiring checks good (continuity and ground checks from the injector plugs all the way to the pcm plug) and good visual inspection. cleaned tb and intake. Could it be bad pcm?? Maybe I need to find shop with that tech2 level computer to check pcm innards. Maybe just change/reprogram the pcm from pcm of nc.

Ideas anyone? Thanks.

 

[The_Roadie]

I'd think a Tech II visit would be the next thing, assuming you've pulled the PCM connectors and looked for damaged or bent pins or chewed wires from the PCM to the coils.

 

[bobdec]

Just reading through his.. During the harness check you performed, on the number 1 injector connector and wiring did you stress/twist and pull the pink +12 volt ignition wire while checking continuity to the other injector pink wires (assuming only #1 is bad, as 6 pinks are spliced together). And do the same while checking continuity on the number 1 black wire to PCM connector C2 pin 33.
As Roadie stated you are now getting into requirements for some more complex tools. Do you know someone with a P12 (2007) PCM you could swap in to see if the PCM driver to #1 injector is OK. The P0201 says PCM did not see +12 at C2 Pin 33 when #1 was NOT commanded on OR did not see ground on that pin when #1 WAS commanded on. Either an open in +12 ign to pink wire on #1, open/shorted injector, open/shorted Black wire to pin 33 or defective PCM driver circuit. With an oscilloscope or a scope attachment to a PC, you could scope the black wire under those conditions. If you go to a shop instead of a dealer make sure they have the correct test equipment to analyze this type of failure not just parts swapers. Also once they start tearing the harness apart you want someone that knows how to fix anything they break.

 

[BigEagle]

Hello, I did not twist and pull or otherwise stress the wires and connections while testing. I did check the pins and all appear to be straight. Brand new injectors. I did pull the coil wire connector on number 1 while running and it made no difference but ran worse when pulled number 2 coil wire connector. Must not be getting any or very little/intermittent fuel on number 1 and therefore a miss?!?!

If I'm going to open it back up and check injector harness again, I decided to check on new harnesses. Found one at GMPartsDirect.com for $54+$13 s&h+=$67. That way I don't have to worry if shop is good at repairing wiring or trouble shooting. Every shop and mechanic is different. At the worse its one more item off the list.

I don't know anyone that can swap pcm's.

Well its off to work now. Talk to ya later.

 

[Wooluf1952]

If the RPM's don't change when you disconnect the wire from coil #1, either the coil is bad, or the wire to the coil is bad. There have been reports of the wire cracking at or near the connector. Swapping coils #1 and #2 should tell you if the coil or the wire is bad.

 

[BigEagle]

So, I finally got the wiring harness in the mail but wasn't able to work on the truck because of all the Holiday activities on the schedule. The wiring harness has been replaced with a brand new one made in Mexico. After reassembly, the truck ran the same. with the same misfire and code. In addition, just to make sure, looking at Wooluf's post I again swapped coils 1 & 2, and spark plugs 1 & 2. Thats the second time but a double check is a double check. A local shop has the Tech2 tester but said to take to the dealer as he has seen this before (or similar) and ended up being a reprogram for the pcm. The dealer wants 90 bucks for diagnostic. reman pcm online is 318.00 delivered and so how much chance should I take in diagnostic. At some point there is a new pcm. Dealer said there is no reflash or reprogramming of pcm's. This is not what i've read.
What's my next move fellas??

 

[BlazingTrails]

Did you reset the pcm during this process? If that doesn't solve the problem I would call pcmofnc and talk to them about it. If you do need to re flash might as well get a tune in the process. And cheaper than a dealership. I would also check the injector, you could have received a bad one.

http://www.autodiagnosticsandpublishing.com/feature/fuel-injector-testing.htm

 

[bobdec]

At this point .. If you still have P0201's I'd pay the $90.00 for a diagnosis.. They should be able to figure out a failing injector circuit in short order. By the way PCM of NC is selling PCM's programmed for $170.00 (including shipping) http://www.ebay.com/itm/2007-4-2-Trailblazer-Envoy-4-2L-TBI6-PCM-Brainbox-Engine-Computer-Programmed-VIN-/251296453281?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a826f92a1&vxp=mtr . So if the dealer says PCM then pay the $90 and give PCMOFNC a call..

 

[BigEagle]

Hello All,
so I checked around and found a local transmission shop that checked the pcm for free. After all , they were working on their atv's. The tech2 said pcm was bad. The mechanic felt bad giving me the bad news. I felt relieved--there was not much left to change/check. So I called PCM of NC and then ordered one($172 shipped). I installed it and it ran perfect right away. I checked around and found a small shop that did the case relearn for $35!!! I drove it for three days to and from work just to double check (200-250 miles) and it runs smooth and quiet. Problem Solved.

Lessons learned? Swapping coils and plugs to see if problem moves, replaced injectors ('cause it was kindof hard to get intake off and didn't want to redo. I could have just swapped injectors to see if problem moved. Thats what i'll do "next time!") Checked the injectors for proper ohms and checked the wiring harness for continuity and crossed grounds/shorts. Then replaced the injector wiring harness with new factor one. It tested good but looked very bad (loom crispy and colors faded/changed).
Then had pcm checked. The best method would have been to test pcm after wire harness check and before changing the injectors and harness--less work anyway!!!!

So all is well now. Thanks for all the help!

BigEagle

PS..The dog is happy too!!!!