Thread: Intermittent PO301 code

I have a 2003 Bonneville SE with about 155k on it, for the last year it has pretty much been sitting since it decided to have a misfire on #1 cylinder. The codes that it had thrown in the past are PO301 and PO201 #1 Injector circuit open. The first mechanic down in Louisiana said it was a dirty MAF. No joy the codes reappeared a couple of days latter. Some off the things I did change where the coil pack, spark plugs and wires, injector, and ICM(which tested out weak). After moving back here to Pensacola I tried to have the car looked at, but my normal shop didn't find anything the first time I took it in. They had said to bring it back when it was misfiring again. About 3 weeks ago it did start it's misfire routine again and we took it to the shop and said that the head gasket was blown. Instead of paying the shop to do the job, I went ahead and did it with my neighbor who is a mechanic. I had the heads resurfaced and the valves done. The car has been running great until today when we where going to the store for groceries, upon start up it was misfiring again. I put the scanner on it and it had a PO301 and PO300 code, about an hour latter I went back outside checked the oil, antifreeze for levels and any mixing. The fluids looked fine, also checked around the gaskets for any fluid leakage. Started the car and the misfire isn't present now. About the only thing I haven't done is change the wiring harness, cam position sensor, crank position sensor, and PCM. If anyone has some thoughts I would appreciate it.

Thanks

Have you checked the wiring to that injector? Like have the car running and wiggle the wiring around to see if you can get it to miss? I've seen weird electrical issues where a wire is broken somewhere in the harness but not enough to cause a hard fault until it was moved around.

Tried that several times over the last year.

Originally Posted by Slick2500

Since it seems to have developed a p0300 I would guess either a bad PCM or either the cam or crank sensor.
And btw I am willing to bet a million bucks your head gaskets were fine, and you only needed intake gaskets.

The heads where warped some when I took them to the machine shop, the old head gasket didn't appear to have any signs it was blown. one other thing it does do from time to time when starting is it doesn't kick over. The starter seems to hang, when you try it again it will start up.

Originally Posted by Slick2500

I am still sure that they were just fine. 99% of mechanics will tell 3800 owners their car needs head gaskets when the intake gaskets blow, because they know that 99% of 3800 owners don't know any better, and they will also only put in plastic intake gaskets from what I have seen.

I want to say bad pcm, but I could be wrong.

I just wish I knew of some where to take the PCM for testing that I could trust. Most Auto Parts stores seem to say the parts are bad after testing just to sell new ones.

I'll pull the PCM this week and take it to a couple of parts shops and go from there. May also take it the local GM dealership to be tested also.

Thanks Scotty, heard bad stories about a PCM replacement from the dealer. Parts stores have them for around $450 then programing. I may have to start digging in some junk yards.

I'm using the right acronym both Autozone and O'Reily's have them. They just call them something a little different.

http://www.autozone.com/engine-manag...7545_551253_0/

http://www.oreillyauto.com/site/c/se...3&make=Pontiac

Yes they want quite a bit for a stock unit, thinking of an exchange with a ZZP unit. The Bonne is stock N/A except for a CAI unit, so it will never be a road burner.

What car did that PCM come out of.

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