Had this problem once before and thought a junkyard computer fixed the problem, but maybe not. You're driving down the road and the car dies. It'll crank fine, but won't start. Fuel pressure is fine. Last time we had it towed to a dealership. They 'thought' it was a bad computer, however they got it started by disconnecting the pcm connector and reconnecting it. I replaced the pcm with one from the junkyard, same model, numbers etc. The van worked fine for about 6 months. We also had a problem where, while driving on the highway, the speedometer would go to zero and then right back. You could feel the trans re-engage. This too happened very infrequently. Someone on this board thought it might be the trans output speed sensor. What I'm wondering, is if this sensor problem could have caused the car to die and it not be the pcm ? Seems strange that 2 pcm's would go bad and especially since the majority on this board think these pcm's very rarely fail. I've had it towed to another dealership to see what they can discover. I think this dealership has a better service department. We'll see what they can come up with.
After they disconnected and reconnected the pcm connector did it fail again before you replaced the pcm with your wrecking yard one? I'm wondering why you messed with the pcm if they got it working.
We also had a problem where, while
A possible cause is the crank position sensor. It is mounted on the transmission in the back, you have to get to it from the bottom. If that fails you get no spark which is what it sounds like your problem was.
The output speed sensor is a different location, and that is a common problem for the speedo doing that.
Since both the crank position sensor and the output speed sensor share a wiring harness I would wonder if perhaps the wiring harness somehow got loose and contacted the exhaust manifold which melted the insulation and shorted some wires.
Frankly there's no substitute for basic troubleshooting. Did they even bother pulling a plug wire and using a test plug on it to at least see if the car was generating spark when you turning it over?
The speedometer problem could be a tranny speed sensor, but strange that it would come back again. My experience has been that when they die, they die. Maybe it is a loose connection to the sensor.
Don't think the bad sensor should cause the car to quit. It will only cause the computer to go into "limp" mode - low gear only.
The dealer called and said it was the pcm. I find it hard to believe that this pcm, even though junkyard bought, same numbers, would go bad, but I guess it is possible. People on this board have said these pcm's very rarely go bad. The scary part is that the car died about 6 months ago, the other dealership said it could be the pcm, but got it started again. I bought the other pcm and put it in and it ran until now and then the car died again. They couldn't get it to start today. I did not like the other dealership telling me it was the pcm but then got it started. The fact that this dealership can't get the car started indicates that it might be a hard pcm failure. At this point I'm not sure. The old pcm died and then ran, maybe intermittent problem, however made the vehicle unreliable. The replacement pcm ran fine for 6 months then died and stayed dead. Maybe I'll spend a little more and get a refurbished pcm and try that.
If the car's been eating pcm's I would look carefully at the wiring loom. It really sounds like the loom is shorting against something. If that is OK then your battery connections might be bad, or cabling to the battery. The battery serves as a natural surge suppressor in a car electrical system and if connections to it go bad then you can have spikes and such on the electrical system. Also maybe the voltage regulator is intermittent and letting the alternator overvoltage the system periodically.
Thanks for the tips. I brought the old pcm to the dealer and they put it in. The car started. Then they put the old one back in and it wouldn't start. So the 2nd pcm is dead. I asked about the pcm going bad and that maybe something else is causing the pcm to go bad. The other ones not dead, but it did die 6 months ago. So I told them to spend another hour or so and check to see if their diagnostics tells them anything, of course with the pcm that works. Hate to junk it, but then really would like to find the problem. I just may get a third pcm and run it until it dies again, if they don't find anything. Any thoughts on going back to a junkyard or spending a little more and getting one at NAPA or AutoZone ?
I think your getting an education in what shotgunning is all about.
The swapping of PCM's is not a real test. If you really want to find out if the PCM's are bad or not, go find another 1993 3.3L Dodge GV that has NO history of trouble with it's PCM and do the PCM swapping with it. I would bet that both PCM's would work in it.
This problem really points to wiring issues or an intermittent sensor. Your computer is older and as a result it does not double check all sensors. So you can have problems with sensors or wiring or other electrical components that do not set a code. The computers in the new cars these days are a lot more sophisticated and will usually set codes if there's a problem. Your dealership techs are used to that kind of vehicle and are apparently helpless when faced with the need to do some real diagnostic work.
Has anyone done even the most basic troubleshooting? Such as cleaning the contacts on the pcm and harness that plugs into it? And using a voltmeter to check the voltage going to the pcm to be sure it's getting a full 12 volts of power? And using a scope on the crank sensor to see if when the engine is cranking that the sensor is sending pulses to the system?
Plugging a scan tool into the system is a first step. But it is not the last step.
You can try another pcm if you really believe that it's intermittent. Frankly I don't think that a wrecking yard pcm is any better than a so-called "rebuilt" pcm. Bear in mind that most of the pcm is dense integrated circuits and you need a tech qualified to do multilayer circuit board soldering and unsoldering and can diagnose computers at a hardware bit level to repair them, the minimum cost of entry for even the tooling to do this is $50K. These "rebuilt" pcms you get are simply wrecking yard pcms that the rebuilder buys pallet loads of and tests out, and if they test out OK they clean them up and sticker them for sale. They might replace a burned diode or power transistor but that's as far as they go.
thanks Ted, I have done some basic things, like unplugging, cleaning and plugging back some connectors, taking the pcm connector off and inspecting the pins and then putting ox-gard on and reconnecting. I did look at some of the wiring to see if I could spot an obvious problem (bare wire, loose connection, etc.) but nothing extensive. Haven't heard back from the dealer yet, so I don't know if they found anything or not. I'll keep trying.
So you think that if I plugged the pcm that will not start my van into another same vehicle, that it might start. Interesting, I just assumed that swapping each in my van and one starting and the other not, proved one pcm was dead.
This is only a suggestion... I don't work on cars anymore.. (too old and fat) however I do still play with them occasionally. A neighbor had a similar problem and a friend and I worked on it to trying to help ..
Well to make a long story short she was ready to junk the car,, had gone through all kinds of problems and dealers and places as you.. My friend (electronics wiz) put a data recorder in the car to check the voltage.. in 4 different locations (same time)while she used the car.... turned out every once in a while the voltage would drop to about 12 volts in the system while the vehicle was running... not enough to set any codes but enough to drive the computer nuts... trans downshift.. speedo crazy... Anyway it turned out the brushes in the alternator were bad (worn) and losing contact once in a while...
As Ted already mentioned ... you really need someone that can get down to the nuts and bolts of troubleshooting... somewhere out there are still some guys that know how to use the computer between their ears and get stuff done... There are an awful lot of parts in a modern auto..could cost some real money to change them all :-)
No, because if there's a problem in your van then it could be the cause, not the part your swapping.
Substitution of components is a good way to test for a bad component, but you have to fully understand it. The more complex the system your substituting the less chance a diagnosis is firm.
For example you see a broken bolt and you substitute it - you have 100% proof that the bolt is broken (although you may not know why it broke) and needs to be substituted. But a pcm is far more complex than a bolt.
for another example you have a problem and you diagnose it as a bad alternator, then replace the alternator with a new one and the problem goes away - that's substitution. However, it's not proof positive that the alternator was the only thing that was bad. It's like 99% proof. But that vital 1% isn't going to go away until you run on the good alternator for several months and nothing bad happens. If you tear down the old alternator and find fractured components then that really decreases chances it's something else. But if you tear it down and find nothing wrong other than diodes - and the diodes that are burned are really high quality ones not cheapo junk ones - well that now increases it's chance that something else in the system is also broken and just took the alternator with it.
In your case the original diagnosis was a bad pcm so you swapped it, but that only got you a 99% chance of proof that the original pcm was bad. As you discovered, when the second pcm went bad and you brought back the first one, it worked. Thus, that vital
1% is now indicating that there's a possibility that something else is bad.
You probably have a solid 80% chance that the original pcm is just intermittent, and more like a 50% chance that the second pcm just didn't last and is truly dead. But enough of a chance exists that it's something in the van that there is no proof positive that the first pcm is intermittent and the second pcm is just dead.
If you tested both pcm's you have in a known good van then you would have that proof positive.
The task now is to do additional troubleshooting of the system (NOT the pcm's) If you can eliminate enough other things you will decrease chances it's something else and increase the solidity of the diagnosis that the 2 pcm's are just bad. That is why I pointed you to the crank sensor and some other parts that have higher probabilities of failure. If those can be tested and found good it will help to be sure that you won't be throwing more money away on more pcms.
The dealer called me this morning and said they spent about 2 hours checking the van. They checked the wiring, the sensors, and whatever else they could check. They did not find anything out of the ordinary. No sensors out of range, wiring appeared ok, no shorts, everything looked good. The vans got
212k on it, but still runs great (outside of this problem). He was pretty honest and said if it were him, he wouldn't put a lot of money into it. They said 'run it until it dies'. Since this original pcm died on me once and then somehow came back to life, I'm a little nervous about it's reliability. So I may spend a little more and get a rebuilt pcm from NAPA or AutoZone and see what happens. This dealer really impressed me by taking the time to run the diagnostics and being pretty honest with me. They could have said $490 plus labor for a new pcm and left it at that. Instead they told me what they thought I should do and then left it up to me.
hey, thanks again for all the tips and comments, I really appreciate it, nick
Hey. they aren't dumb - old guy comes in with a 93 GV with
210K+ miles on it - they know your probably going to be shopping for a new one in another 20-50K and they want your business! ;-) And old guys tend to know a lot of people in the community and talk to 'em. ;-)
Seriously, you might just take a look at what they have on the used lot and consider doing a trade-in, or buying a used one and selling yours via private sale, rather than buying another pcm. Since yours is running well now, but you have reason to believe there's a potential for failure there, nows the time to sell. I've personally been burned once by holding onto a vehicle that I knew had some potential trouble but I was lured by the thought that I might be able to squeeze just one more year out of it. Of course the damn thing broke down before I planned and once that happens the only people who are going to buy it out of your driveway is the wrecker who wants it for scrap steel.
It might only cost you a few grand and you might end up with something almost 100K miles younger. There's lots of 94 & 95 minivans out there around the 110-120K age bracket right now. And generally after the 10 year mark used vehicles take a significant depreciation drop. It certainly doesen't hurt to look. And we are getting toward the optimal time to buy a used vehicle espically from a dealership. Around about January, the dealerships are full of used vehicles they have taken in trade from people buying new ones, and since it's right after Christmas, most of the people who would normally look for a used vehicle are tapped out from Christmas and they haven't got their tax refunds yet. You could buy another van then just park yours in the driveway for 2-3 months as a spare until your sure the replacement is good, then sell it when vehicle sales pick up a few months later.
I personally think the 91-95 years were really good vintage in those vans, with the only weak point being the tranny, and ABS (with the exception of 94 1/2 - 95 which was a different system) if it has it. Stay away from the 96-98 vintage, Chrysler did a major overhaul in 96 and changed a lot of things, and they were still diddling with the tranny in later years until I think they got the last of the bugs squished in the 2002 timeframe.
Hey, thanks everyone for the great replies and suggestions. Ted, you're probably right, I should consider dumping it. It's tough, because I know what I've replaced,fixed and repaired, and probably too attached. It's e-check time and that might be the 'last straw' -- if it fails, I may park it and look for a replacement.
I replaced the water pump last summer when I changed the timing chain. I checked all around trying to see where it was coming from. Thermostat housing looks dry, water pump very dry, hoses look fine. That's why I'm thinking it's coming from the overflow bottle. Doesn't overheat, no water in the oil. Thermostat works and water is flowing. So I'm thinking the head gasket. Would like to find another cause though, not going to spend money on a head gasket repair. Van has 212k and there are a few other problems that tells me it's time to let it go.
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