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Intermittent PO301 code

M

max harris

New member
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.
 
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.
 
Slick2500 said:
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.
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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.
 
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.
 


Slick2500 said:
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.
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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.
 
max harris said:
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.
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No not really, I've took the alternator from my car in to Napa once and their machine said it was just fine right after I had my friend hook the car up to his big machine at his shop that said the alt was bad. Long story short the alt was bad, because when I replaced it the car stopped randomly dieing.
 
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.
 
dealer is the only one who can reset your pcm local, unless you find a local with a tuner. parts stores dont test pcm's nor does the local garage.

and the dealer needs the pcm in the car. and iirc the test to see if the pcm is bad, is to replace it, what the dealer will do.
 
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.
 


damn those are expensive.

you could buy one used on line, then ship it to some one like me who has a tuner, then i can flash your year bin file to it and ship it back for far far less lol
 
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.
 
id double check things before swapping the pcm. zzp tunes are not the best out there. you'd probably like a overkill tune better, n/a guys say they make a difference

pretty sure this pcm i got laying around here that would take a 03 bonnie bin too.
 


it came from a 02 gp. if it takes your year bin, it will work. its got a 03 regal bin on it now. but the guy i set it up for is super dragging his feet, so first come, first served.

i dont claim to be a tuner so it will be a stock tune. but i can delete codes, evap or egr. raise the speed limiter. set the fans to a lower temp. make the cat test stop if you want to delete your rear o2 sensor. (for header and no cat set ups)

also set your vin# in the pcm so its correct like it should be.
 
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