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Old 05-17-2015, 03:16 PM   #1
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1996 SL2
Dizzy '98 SL2 200K+ Intermittent P0340 and random misfire issue.

Re: Where is J3D03 (Circuit 633/Cyl #4 signal)? on '98 SL2 200K+ Intermittent P0340 and random misfire issue.
Related: Saturnfans thread 43380

I've read related threads that have good information, but I need some help following through. To get to my question go to where it says ***Question***

Also see attachement for the troubleshooting chart that I'm trying to follow.

My problem can best be described in this sequence of events.
My motor mount is bad, so I was driving to my friends to replace it. But he was sick, so I visited with him instead. When I started the car to go to the store, the car was running poorly, with MIL P0340 (Camshaft NOT Crankshaft position sensor), and random misfire. But when I first drove there other than the motor mount noise when the car was cold the car ran ok. I tried warming up the car, and when the temp was to the midway point the car started running ok, but then on the freeway home, the car starts running poorly again, and I pull over and turn the engine off. I waited about 10 minutes, then started the car, and it ran ok and I made it home. Since then it has mostly been running poor, but I haven't tried driving it far.
This is clearly an intermittent problem, not a total failure, and I don't think it's temperature related (probably just a coincidence). It's acting like a bad wire, or connection.

I have replaced the ignition coils, and checked almost every step Chart 1 of 2 in the 98-T-49A. Because my spark plugs look ok, and wires tested ok, and I had replaced them less than 20K ago. I will replace the plugs with copper plugs next time and gap them at 0.40 as soon as I can. Chart 2 of 2 starts with a back probe of J3D03 (Circuit 633 or #4 cylinder signal - there is no actual camshaft sensor, it just emulates the signal).
The car can idle, but sometimes the gas is rich and it will stall.

How do I find this to backprobe? I know it's a brown/white wire, and I've looked at some pinout diagrams, but I can't make sense of it, and figure out exactly where the pinouts are.I saw a brown/white wire, but my color vision is not what it used to be. I was also going to test the Crankshaft sensors while I was at it although you would think I would get a Crankshaft code if that was the problem. Since this is intermittent, I would think that this would be a big clue as to what the problem is, possibly a wire. I had a radiator leak awhile back that I fixed, so I'm thinking maybe the moisture got into the jumper. Visual inspection shows the connector to the EI module is blackened with soot, but the connector is clean where it connects.


Attached Images
File Type: jpg PCM_IGNITION_CHART.jpg (60.3 KB, 8 views)
Attached Files
File Type: pdf CMP SENSOR CIRCUIT PERFORMANCE CHART 2 OF 2.pdf (88.2 KB, 3 views)
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Old 05-17-2015, 07:23 PM   #2
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1999 SL1
1999 SL2
Default Re: '98 SL2 200K+ Intermittent P0340 and random misfire issue.

The P0340 sets because you have an issue with the spark plugs, and the wires. Start with that. Don't overthink this.
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misfire, p0340, pcm, sl2

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