QuestionQUESTION: Hi Roland,
After an oil change at a local shop, our van would not start. We found the wire harness wires had melted and the computer was fried. We replaced the computer and wires and the van started. BUT no working radio,wipers, windows, locks, climate control.Lots of internet research, including your post about these things working in accessory mode, but not in run which is exactly our problem. We replaced the fuses and ignition switch. Nothing. We lubed up the lock cylinder. Nothing. Any other possibilities?
ANSWER: Hi Shawn,
I have the '02,'04, and '05 manuals (paper,CD,CD) but so far have just reviewed the 02 because it is more accessible. It appears that there is an issue either with the internal resistors of the ignition switch, or with the body computer which 'senses' the position of the ignition switch by reading the various resistance values of the different positions of the ignition key.
My question to begin with is whether the body computer might have been involved in whatever incident led to the 'computer' being fried (which computer was that? the pcm, bcm or ?)?
Are you sure that you got the right replacement ignition switch and if body computer was fried the right part number body computer?
There is nothing but two wires between the ignition switch and the body computer and if either one were shorted or open that would probably kill the ignition switch function entirely, so I have to suspect either a faulty internal resistor set up in the switch or a faulty/mismatch at the body computer.
I can tell you what you should observe at the 2 pins (on 2 separate plugs) at the body computer as you move the ignition key (not the exact values of resistance, but that the resistance should change with each position of the key), if you want to measure that. The body computer is under the dash, on the firewall near the brake pedal and it has 4 large 34-pin plugs and one small plug for reference.
Let me know if you have a volt/ohmmeter and want to check out the resistances, and also comment upon any of my questions or assumsptions. But it does appear that the only reason things work in accessory mode but not in run mode has to do with the way the body computer is seeing those different resistance values created in the switch.
I like the good old days when there were wires and not sensors! Let me know if I am far off the mark from what other info you have already received. I will insert the CD's and see what else I can learn.
Roland
PS: May I ask a favor of you? I would appreciate your rating my answer by clicking on the "Thank/rate expert" button below/left. Please notice the question just below the ratings which asks if you would like to nominate me to be 'volunteer of the month'? That recognition is based on the number of 'Yes's I get from questioners like you, one 'Yes' per each answer being allowed. Thank you in advance for your giving me a 'Yes'. This is simply a recognition of me that will appear at the Top Experts page of the site, and would help to publicize the fact that we give competent Chrysler repair advice.
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QUESTION: Hi again,
Thanks so much for the info and I was happy to rate you below. I would like to learn more about the body computer, since I looked at that briefly and wondered how it played into all this. The computer that fried was the ECM. We think it got friend when oil was dripped and wires melted.
We ordered the ignition from Chrysler. Honestly, I think I ordered an '01 part forgetting that I have an '03. Would that make a huge difference? It looks exactly the same. But I have a suspicion that it's wiring b/c when I used a light tester to test the wire voltage, I found that when I ground out one of the wires in run mode, all the electrical worked. But if I left it grounded, and then started the engine, it popped the fuse. Then I rigged it up to stay grounded with switch to by pass the fuses just to give my wife windows and heat, but it almost caused a fire :) (whoops!)
Thanks for your speedy replies. All of your posts have helped us so much!
AnswerHi Shawn,
I wish I had an '01 manual to see if there is any major difference in the wiring of that switch. However, it may even be a subtle difference in that there are about 6 resistors in the switch and changing any one of those could be involved over the 2 year period. Unfortunately the manual doesn't show the resistance values of the resistors. However, why not check with the dealer parts counter and see if the '01 and '03 switches have the same part number. If not, I'll bet that could be the reason for your problem.
The body computer is essentially the brain that takes info in from sensors and switches and dispenses instructions out to all the electrical components. So for example it uses the input from the ignition switch resistor bank to tell the front control module, part of the integrated power module (fuse/relay box in the engine compartment) which circuits to supply power to, etc. Thus, it seems to think when you are in 'run' that you are in 'start', possibly, which would 'shut off' all the things you are missing because the power to those auxiliary devices isn't desireable to have drawing on the battery when it needs to give its maximum current to the starter motor. At least that is one possibility I can imagine.
So do check that part no. issue out and let me know what you find. I'll do some looking in the manuals in the meantime. Do you recall which wire you grounded and what was the by-passing you did that almost caused a fire? That info might be helpful to know.
Roland
Many thanks for the nomination...you are entitled to do another.
