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Old 09-13-2009, 11:43 PM   #1
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Default Random misfires with code P0321

I could use some help. I have been fighting misfires at idle and underload. The misfires are random and happening on all cylinders. I am getting code P0321 and at times P1361. I have a FSM and the DT refers you back to P0321. My scanner say it a Halls 18x interrupt lost signal. I replaced the crankshaft sensor, but still getting the error. The harmonic balancer was replaced about 3 year ago with the crankshaft sensor prior to that. I did notice an antifreeze leak that was dripping down by the sensor. (replace the waterpump, heater tube o-rings, LIM gasket and rebuilt the */C snout as the coupler was making noise.

Here'* were I'm at: in following the DT for P0321, the test at CKT 647 at the PCM connector RB6 (light blue/black) shows just under 5 volts with key on, engine off. With engine on the voltage reads 2.9 to just over 3.0. Could be the meter, but I don't think so. My problem is, the DT reads, does the voltage read approximately 2.5 volts? Yes or No. If the answer is YES, then the problem is a poor connection at PCM RB6 or faulty PCM. If the answer is NO, then it is a poor ignition module connection, poor connection at 8-way ignition jumper harness connector or faulty ignition control module. Is 3 volts a YES or NO? CKT 647 checks OK; not grounding nor open with very little resistance.

Opinions would be great. I will be driving the car tomorrow on the freeway (20 miles each way). I have a volt meter hooked up as well as my scan tool. I suspect but can not confirm that the misfires are happening at the high 2.9s and 3.0 range.

I need to get this resolved as the backup vehicle I am using will be going away later in the week.

The vehicle in question is a 1994 Bonneville SSEi.
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Old 09-13-2009, 11:51 PM   #2
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If I remember correctly the 94 has problems with the PCMs.
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Old 09-14-2009, 12:15 AM   #3
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Here'* a new wrinkle. I just went our to move the car onto the driveway pad. I started it up, had an apparent misfire, then a half a second to a second I lost all power in the car. Everything, flat dead. Checked the battery and it is just fine. Could my probe to the PCM have caused the problem? Would a fusible link cause everything to go dead?
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Old 09-14-2009, 10:29 AM   #4
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For everything to go totally dead the battery and or cables are the problem. Did you check both ends of all the cables? It'* also possible the cable it'* self failed. Test the cables. This is all covered in the tech info area.
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Old 09-15-2009, 10:01 PM   #5
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The loss of total electrical power has been solved.Somehow, the positive side connection at the battery loosen up. Taking it apart, cleaning it well and reassembly with torquing the bolt fixed the issue.

Now back to the misfires. I took the coils and ignition module off. There was some corrosion and lots of dirt and some oil between the bracket and ICM plate, the ICM plate and the back side of the ICM. I cleaned that all up and put it back together dry. It is now misfiring at a faster rate. I am still reading 2.9 to 3.1 volts at the PCM on CKT 647.

Question:
If the PCM is receiving 2.9 volts, then the PCM should be receiving a "spark reference" signal. Am I correct on that?

If that is true, then I should replace the PCM. Am I correct on that? Otherwise, I need to replace the ICM. Am I correct on that?

I could really use some guidance on this. As I said, the FSM is not that clear on this.
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Old 09-16-2009, 08:18 AM   #6
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Trying to decide if the PCM is bad is more of a guess once you are bald from pulling out all your hair than it is an exact science.

From what you wrote, the FSM is telling you replace pcm if you have the readings you do. Cleaning all the various things is good and will help in the end....but to the actual problem. Yeah.

The 94 and 95 pcm'* appeared to have the largest failure rate of any years going. So much that they are sometimes still stocked at parts stores. Stocking means demand.

I'd probably aim to a junkyard for a better price if possible since toms of cars used that same pcm and you can use any of the compatible ones if you simply pull the access cover and change the blue eprom chip.
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Old 09-16-2009, 04:05 PM   #7
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Here'* a shocker, all of the auto recycling centers in my area are now gone. I knew some disappeared, but come on, all of them? There used to be a concentration in Woodinville, that site is now being developed as a sewage treatment plant. Guess that'* an upgrade.

I can purchase a reman for under $100, which always bothers me. But if you have to, you have to. I'm not seeing a new one around here. Not sure if they can be had. I am going to take a fuel pressure reading just to make sure if that'* not a problem. Shouldn't be with a P0321, but.....

I will probably venture to Autozone later today or tomorrow to pick one up and give it a try.
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Old 09-17-2009, 03:03 PM   #8
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replace the ICM and all your problems will be gone,i had multiple missfires car ran like a #[email protected]$ put the new ICM in smooth as silk.You are better off buying a new one though from advaned auto to go for like $150 but it is well worth it.
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Old 09-18-2009, 01:56 PM   #9
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SCO99888
What brand did you install? AC Delco, BWD, Standard, or one of the auto chain brand names (Duralast, Master Pro, etc.)

Has anyone else had experience with any of the chain brands?
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Old 09-21-2009, 09:23 AM   #10
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BWD Ignition Module/Control Unit,i bought mine from advanced auto for $133.
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