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Blowing Injector fuse after running and warms up, scan code P0650

Tiny
WILLIE7777
  • MEMBER
  • 2001 PONTIAC GRAND PRIX
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 188,000 MILES
Runs Rough, Scan tool doesn't show a misfire. Blew an injector fuse, Replaced injectors, checked engine wiring, replaced fuse, runs for a while at temp 180 degrees for a bit, Seems like till the PCM gets warm and blows the injector fuse. Would not take a fuse till it completely cooled, replace the fuse and it starts, runs rough, Scan tool showed P0650 faulty indicator light, harness short or open, and or a faulty PCM. I'm gonna check the wiring in the dash and the bulb, and check the PCM wiring. What is the likely hood that it's a faulty PCM with the symptoms above? Would a PCM do that? If it was a dead short it wouldn't take a fuse at all and it don't after it runs for a bit probably 30 minutes or so I'd say or more than the fuse blows and you have to wait till it's cool again replace the injector fuse than it'll start. I don't want to waste money at a Dealer till I'm sure It'll be helpful.
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Monday, April 6th, 2015 AT 8:36 AM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
It sounds like an issue with the PCM. Something is getting warm and failing. As you mentioned, a short would exist all the time, no just when warm.
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Monday, April 6th, 2015 AT 8:46 AM
Tiny
WILLIE7777
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  • 4 POSTS
Okay just discovered another issue I'm not getting any input from the MAF sensor. Could that contribute to the issues? Overloading the injector fuse and things of that nature or overloading the PCM and causing it to overheat on certain components and blowing the fuse? Definitely interesting. Wonder if the harness is bad or if the sensor is shot getting ready to ohm it out right now.
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Monday, April 6th, 2015 AT 12:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
It wouldn't blow the fuse. Check to see if there is even a power supply to it from the PCM.
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Monday, April 6th, 2015 AT 5:41 PM
Tiny
WILLIE7777
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Yeah it's got power, the OBDII dont get any readings from it at all. Turns out the p0650 was just a blown bulb, then it gives me the MAF sensor code and I looked at the monitor for readings while it was running and I don't get any feed back from the MAF sensor at all. I ordered a sensor we'll see what happens. If the sensor doesn't fix the readings then it's gotta be a PCM issue, the PCM would give me something from that. I'm wondering if it isn't overloading the PCM to compensate for the fuel cause it's definately burning a lot of gas and overheating a circuit and blowing the fuse when the PCM gets warm? Or if it had ruined the PCM because the SES light was burnt you couldn't even tell there was an issue except rough idle. Not sure what to think.
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Monday, April 6th, 2015 AT 6:59 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
If there is no reading from the MAF and it is getting power, then the sensor is bad. See if that takes care of the issue. Another thing to keep an eye on is the coolant temp sensor. If it is sending a false signal to the PCM, it will over compensate the fuel mixture to run on a very cold day. The only concern I have is that I don't see how either of these issues would cause a fuse to blow.
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Tuesday, April 7th, 2015 AT 4:30 AM
Tiny
WILLIE7777
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That's my worry too. I'll get the MAF put in and check the wiring at the PCM and let it run till it blows again if it does, I'm just curious if it's been like that for a while and the PCM has been overcompensating for a bad MAF sensor and its overloaded circuits in the PCM. I'll clean grounds. Check the wiring and let it run and see if it blows agian, then if it does see what kind of reading I get at the fuse box. That fuse from what I understand only supplies power to the fuel injectors at least that's what I've read. So I still think I have a PCM problem. I'm at the point I hope it's a bad PCM because I'm at a little loss.
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Tuesday, April 7th, 2015 AT 7:26 AM
Tiny
WILLIE777
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OOK. MAF sensor swapped now I get good readings from that. Now I get a cylinder #1 Misfire code, P0301 In the list of possible issues could be the PCM, Plugs, wires, and injectors have all been changed. With the blowing of fuse symptom, Seems I got a bad PCM would that make sense? Wouldn't be a bad plug would it? If it's blowing the fuse after it warms up only makes sense. What DO you think?
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Wednesday, April 8th, 2015 AT 8:08 AM
Tiny
WILLIE777
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  • 3 POSTS
Coil packs have been changed also forgot to include that.
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Wednesday, April 8th, 2015 AT 8:28 AM
Tiny
JACOBANDNICKOLAS
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There is a good chance it's the PCM. The only other thing I can think of is if there is a poor connection at some point and the power is arcing. That would cause the connection to overheat and possibly blow the fuse.

Just for the heck of it, before you replace the PCM, pull the #1 plug and make sure nothing happened to it. Make sure it has the proper gap, is clean, dry. Let me know what it looks like.
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Wednesday, April 8th, 2015 AT 10:57 AM
Tiny
WILLIE777
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I thought the same thing pulled the plug and looked at it, Plug looks good not black or fouled like the cylinder would be getting oil, or any evidence of a coolant leak. I get a solid spark from the high voltage packs (their new) but obviously you could get a bad one. So the packs and ICM should be okay. I monitor it and the misfire is intermittent, it'll misfire for a few minutes then run okay (according to the SES light and the scan tool) then is comes back and blinks. Any possibility there's an issue with the injector plug connector itself or more likely the PCM? What if the driver in the computer for that cylinder is screwing up and overheating? Just throwing Ideas around not sure where to go from here without a PCM swap. Any thoughts would be very helpful.
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Wednesday, April 8th, 2015 AT 11:19 AM
Tiny
JACOBANDNICKOLAS
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It could be any of the things you mentioned. What I would suggest is to get a noid light (rent one at a parts store) and check for a electrical pulse on that injector. While checking it, move the wiring around to see if there is a change in the power supply to the injector. Also, make sure where the wiring plugs into the PCM, there is no corrosion and the connection is good.
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Wednesday, April 8th, 2015 AT 7:13 PM

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