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P0202, P0204, P0300 2004 Grand Prix N/A *Need Help*

S

Stealth170

New member
I have a 2004 Grand Prix 3.8 N/A with 153,xxx miles.

The car has been running like a great piece of crap with black soot on the rear bumper that has been coming out of the mufflers. Car is throwing P0202, P0204, P0300 codes. Most recently the check engine light has been blinking and I get 6 total codes with all three of those along with the "in progress" codes. I know the codes are injectors 2 and 4 along with random misfire. I ohm tested all 6 injectors and they all came back around 13.3-13.4 after the car running for a few mins, and then after sitting overnight they were all 12.1-12.2.

While I was testing all of those I decided to pull the plugs and wires and replace them as they were factory. Replaced with brand new Delco wires and delco iridium plugs gapped at .060 (both factory). After replacing all of these the car ran the same. (which I didn't expect any differences)

What should be my next step. I was thinking of trying to test voltage at injectors 2 and 4 to see if they are getting the required voltage from the PCM. And possibly just buying another PCM and replacing it as there are a few boneyards within a few miles that have them for $50.

Am I missing anything? Any help would be appreciated.
 


oh take a side bulb out of the head light, the small light, un plug one of the suspect injector plugs and push the bulb socket end in the pkug, go fire up the car, see if the bulb is flashing or now, if not its not getting power.
 
Yeah. I looked up the codes. I just swapped injectors from cyl 2 and 4 with cyls 1 and 3, cleared the codes and started it up. Codes came on again same ones. So I am to check voltages at injectors next. If voltages are low or erratic a bad PCM or short in the wires is likely correct.
 
see someone here have a injector problem and it was caused by rubbed through wires at the pcm harness. if you have a open cone air filter this is more possible to happen.
 
Hmm. Interesting that you say that. I pulled the PCM and the middle harness does have at least 2 wires that the silicon is rubbed off of a little but and some strands of the braid is exposed. Do you have a diagram of those wires to see which ones these wires are?
 


i would solder only, with shrink tubes so its a weather tight permanent repair.

it depends if the bad area will reach after you cut it, one splice is better then 2, so if you can cut the bad area and re splice it back together thats best, if it wont reach any more you'll have to add some wire and make two new splices.

do make sure you strip the wires back till you see clean shinny copper wire, if its brown and tarnished the solder wont stick at all.
 
oh. after you cut the wire, before you solder, dont forget to put the shrink tube on the one side of the wires. you need to slide it over the splice, then use a lighter to shrink the tube tight.

search you tube, lots of good soldering vids. how to twist the wires to what solder to use. i use thing flux core solder from radio shack. runs like 5 bucks a tube. the tube i bought 4 years ago is just coming to its end.

HF has cheap soldering irons if you need one, and shrink tubes. both run around 3 bucks each.

having a soldering kit is one of them things we all should have on hand, its the one thing you never know when you'll need it till you need it.
 


I replaced the two wires that were frayed. One was green with black stripe, other was blue with black stripe. Both wires corresponded to injector 2 and 4 plugs. (Ohm tested to confirm). Who would have guessed. So I cut, spliced, soldered, & shrink wrapped them. Plugged back in the PCM, replaced the neg battery terminal, cleared the codes, started it up and now I only get a P0300. The P0202 and P0204 is gone.

I still have the P0300 code though. Engine is stumbling like mad. There were two other wires in the same bundle that were melted a little bit but they were not broken or had any braid exposed so I didn't replace those sections. I'm thinking now that I probably should.

Is there any other items that could cause the P0300 besides that?
 
you did say you changed the plugs and wires right? double check the plug wires are on right. it happens, hell i crossed 2 up my self not to long ago, fired it up ws like ok some thing on wrong, double checker 2 were wrong.

58ea74a.jpg
 


Well I tested the coils and the wires. All 6 had no issues and showed spark. I just did the plugs along with the wires. There isn't an external fuel filter (its in tank). I'm stumped.
 
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