1995 Plymouth Neon

Tiny
KBLAKE87
  • MEMBER
  • 1995 PLYMOUTH NEON
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 82,200 MILES
Hello! My car shakes a little when Im idling, but my main problem is after I drive on the freeway. It runs fine and will go to max speed with no problems. Once I get off the freeway and stop it stalls. It always starts right back up, however the check engine light comes on. Ive just changed the oil, spark plugs, and ignition module. Would you be able to help?
Thanks!
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Sunday, April 25th, 2010 AT 1:43 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
Hi kblake87. Welcome to the forum. When the Check Engine light comes, there is a diagnostic fault code in the Engine Computer's memory. That code will indicate the circuit or system with the problem, not necessarily the defective part.

If you want to try to read the codes yourself, it is by far the easiest to do on Chrysler products. All that's required is to cycle the ignition switch between "off" and "run" three times in five seconds, then leave it in "run" without ever cranking the engine. Then you count the flashes of the Check Engine light. It will flash two-digit codes as a series of flashes with a short pause between the first and second digit, and a longer pause between each code. If you can get those codes, post them in your reply.

Caradiodoc
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Sunday, April 25th, 2010 AT 1:54 PM
Tiny
KBLAKE87
  • MEMBER
I was already at Advanced Auto Parts when I received your reply so I asked them to check it for me. They said what you suggested to do was for an OBD 1 but I have an OBD 2, so they could just use the diagnostic tool. When they did two codes came up.

P0352 Ignition Coil B Primary/Secondary Circuit Malfunction

P1391 Manufacturer Control Ignition System or Misfire
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Sunday, April 25th, 2010 AT 2:36 PM
Tiny
CARADIODOC
  • EXPERT
You're getting some misleading information from a parts salesman. I doubt they're trying to be dishonest, but they might be adding some unnecessary confusion to the story.

On-Board Diagnostics version 2, (OBD2) started with '96 model cars and trucks, although some late production '95s could have it already. All that means is you have a second oxygen sensor after the catalytic converter to monitor its efficiency. It has nothing to do with reading diagnostic fault codes, but OBD2 cars DO have a lot more possible codes that could be detected, mostly related to that second O2 sensor.

The code reader they used on your car works all the way back to '83 models and will work up to all '03 models and some models up to '06. Chrysler is the only manufacturer that also lets you retrieve the codes by cycling the ignition switch. That also works on all models from '83 on up, but beginning with OBD2, the numbers show up in the odometer window instead of flashing the Check Engine light. I forgot to mention that previously. With OBD2, there are too many potential codes that they ran out of two-digit numbers. Also, in an effort to standardize codes among manufacturers, the "P" codes like those they found for you, are related to the powertrain and represent the same thing regardless of the brand of car. They are four-digit codes now so it's easier to use the odometer to display them. Less mixup from counting incorrectly too.

The advantage to using the code readers is they can display the description, not just the number that you have to look up in a service manual. Also, reading codes, which is all their equipment can do, is just a tiny fraction of what scanners, (hand-held computers) can do. The scanners used by mechanics read live sensor data including while on a test drive, will turn on relays and other circuits, and can reprogram the numerous computers on your car. None of that has anything to do with whether it's OBD1 or ODB2. You can prove this to yourself by cycling the ingition switch as I described. The flashing Check Engine light, (on older cars) is also used by mechanics for a quick check to see if any codes exist but it only works for the Engine Computer. The scanner will read those same codes, but it MUST be used to read codes stored in the body, anti-lock brakes, air bag, and on most cars, the transmission computer.

Diagnostic codes can also be read on GM vehicles but you have to crawl under the dash to connect two terminals in the diagnostic connector, then you read them the same way by counting the flashes of the Check Engine light. Scanners will read those codes too. Older Fords required connecting a light bulb under the hood, then doing other things to make that bulb flash the codes. That was a pretty involved, time-consuming process. Even using a scanner on those older Fords required an extensive procedure before the codes would be displayed. Now you can see why Chrysler's system of just sitting in the car and turning the ignition switch is the best.

The codes you got point to a problem with an ignition coil or the Engine Computer. There are two coils built into one assembly. Each coil runs two spark plugs. Your mechanic will perform tests to determine how to repair the problem, but if you want to tackle this yourself, I would replace the coil pack and try it. Normally I don't like throwing parts at a problem without knowing for sure they're defective, but in this case, the possibilities are rather limited. Chrysler has typically had very little trouble with Engine Computers, especially when compared to other manufacturers, so it would be the least likely of the two suspects. The wiring should be inspected too for breaks, bare spots, and corrosion, particularly in pins in the connectors.

Caradiodoc
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Sunday, April 25th, 2010 AT 8:56 PM

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