2001 Chrysler Town and Country PCM Problem

Computer problem
2001 Chrysler Town and Country 6 cyl Automatic 137, 00 miles

I had my PCM and CAM shaft posistion replaced at a Chrysler dealer about a month ago. They found that the "PCM burnt up caused by a short in the CAM shaft position sensor." I also replaced the spark plugs and air filter, complete MOPAR fuel injection service, oil change and rear hatch props replaced.
Within a few days my engine light came back on and my side doors and back hatch worked inconsistently (wouldn't fully lock or wouldn't automatically open.) Now the van has quit again and back in the shop.

What else could be the cause of these problems? Are these problems typical for my vehicle? Were any of these recall items?
Do you
have the same problem?
Tuesday, March 2nd, 2010 AT 4:29 PM

1 Reply

I can not argue with someone else's diagnosis when I can't see the vehicle and they aren't here to defend themselves, however, I can argue with their description. A sensor will not "burn up" a computer. That is a response from someone who is looking for a quick explanation so he can get it over with and get back to work, or from someone who relays the information between the mechanic and you, and the message gets lost in translation.

The engine computer supplies 8 volts to a couple of sensors on the engine. If one of those sensors, or the wiring to them becomes shorted, the computer shuts the 8 volt power supply down to protect it. That results in a no-start or stalling condition. The 8 volt supply will not turn back on until the ignition switch is cycled off then back on after the short is gone.

The sensors also have signal wires that can become shorted, or "grounded". Part of the time the sensor grounds that same wire. That's how they work, so obviously the computer was designed to accept that condition.

When they redsigned the minivans for the '96 model year, the Chrysler engineers copied the other manufacturers in trying to hang a lot of gimmicks and toys onto them because those "features" are what sells vehicles to people who are relatively unknowledgeable about cars. To accomplish things like dome lights that slowly fade out, lights that turn off automatically, a dual zone heater, and power sliding doors, engineers have added computer controls to every imaginable circuit or system. They add a high degree of complexity to the vehicle with a corresponding high degree of difficulty diagnosing problems. Up through the '95 models, Chrysler had very little computer trouble. GM has always had a lot of expensive problems caused by their computers, and Chrysler started having huge reliabillity issues with their '96 models too. For that reason, that's the first thing mechanics suspect now when trying to diagnose a problem. Along with that, most computers can have their software updated. That often isn't attempted without first replacing that computer. Especially for intermittent problems, the mechanic may be reluctant to update the software in hopes it will solve the problem, because if it doesn't, you will have to come back again later. That adversely affects his "fix it right the first time" reputation. The emphasis is on "first time", not "fix it right". Replacing the computer AND installing the new software increases the chances the problem is solved. Most customers are happier in the long run having their vehicle fixed in one visit vs. Having it repaired at a potentially lower cost that involves two or more visits. I saw that in the tv repair industry too. Replace a few extra parts at extra cost to insure it was repaired, and customers were happy. Try to save them a few bucks because it might not need some of those parts, and they will scream if they miss their football game. This is partly why people in the service industry have bad reputations for replacing parts that aren't needed. Unfortunately, most car parts are expensive. The mechanic has to juggle making you upset with a high repair bill and extra parts to insure the car is repaired, with trying to save you a lot of money but the problem might not be solved yet. Regular customers who are patient and understandng will get better treatment of their wallets.

Now that that's out of the way, there ARE instances where there can be multiple parts needed to solve a problem. One example had to do with Body computers locking up due to voltage spikes from the power window and lock circuits. The repair involved replacing the computer with one that was more tolerant of voltage spikes, and replacing certain relays that were known to cause voltage spikes. Either part alone would have greatly reduced the frequency or totally eliminated the problem, but all the parts were replaced to be sure.

As for my comment about "lost in translation" every once in a while, a customer would look me up to thank me for fixing their car. When they described what they were told, I didn't even recognize it as what I told the service advisor. Those middle men usually aren't car experts. They are proficient at talking with customers in terms they understand and often get the mechanic's version mixed up themselves.

Since the Check Engine light came on, there was a diagnostic fault code to tell the mechanic which circuit or system had the problem. That should make diagnosis easier, but I don't think it is related to power door problems.

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Thursday, March 4th, 2010 AT 7:08 PM

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