I am here to save the day. Well, at least that is my fantasy.
The PCM is the Power Train Control Module. That's Chrysler's name for the Engine Computer. That does not have anything to do with the anti-lock brakes.
The data buss originates in the Body Computer and is the wires the dozens of computers talk back and forth to each other on. Be sure to check the fuses under the hood and inside the car. You will have to visually check the big ones under the hood, but for the smaller ones, there are two tiny holes on top, one for each test point. Use a test light to check for voltage on both test points for every fuse of that style. The ignition switch must be in the "run" position or the engine should be running. Some fuses will have 12 volts on both sides. Those are good. Some will have 0 volts on both sides. Those circuits are currently turned off and are not related to this problem. You're looking for any fuse that has 12 volts on one side and 0 volts on the other side. Those are blown.
There is a current surge that can cause nuisance fuses blowing when the battery is reconnected, and if the cable clamp was loose and arcing, it is even more likely multiple fuses would blow for no reason. A blown fuse is the cause of the "No Buss" message in the odometer display over ninety nine percent of the time. When it goes down, the computers cannot share information about operating conditions, sensor readings, and systems the driver has turned on. Also, it is the Body Computer that tells the other computers to wake up and do their thing, so with no data buss, none of the other computers will work. The fact the Engine Computer is letting the engine run suggests there is a back-up mode that allows limited functions so you are not sitting on the side of the road.
At this time I do not have a good answer, (or one that I can make up), for the anti-lock brake fuse problem. I have a trick for powering up a circuit for testing while preventing another fuse from blowing, but in this case there is just a computer and a hydraulic controller to look at. Simply unplugging them should stop the fuse from blowing, and plugging just one of them in will identify which one is causing the problem. Neither one has a history of shorting, but if I were to guess, I would suggest the computer. All computers have a diode in them between the 12 volt feed wires and the grounds. Diodes are one-way valves for electrical current flow. In one direction they act like a dead short, or piece of wire. They are installed in this application backward. That makes them become a dead short when the battery is connected backward. That short forces the fuse for that circuit to blow, thereby saving the rest of the circuitry. All you need to do is connect the battery correctly, replace the blown fuses, then look for other things that might have been damaged.
For the running problem, "it is not right" does not give us anything we can analyze. That is like telling your doctor over the phone that you are in pain. Unless you are specific with the symptoms and observations, he has no idea if you have a hang nail, a stomach ache, you cut your foot off with a chain saw, or your ex-girlfriend came back. The Engine Computer and Transmission Computer in particular go through a learning process as you drive to learn the characteristics of various sensors and the amount of mechanical wear inside the transmission. Some of that information is relearned within a few seconds. Some requires multiple drive cycles when a specific set of conditions are met. For example, when the battery was disconnected and reconnected, idle speed will usually be too low until the Engine Computer relearns "minimum throttle". Until then you might have trouble getting the engine started unless you hold the accelerator pedal down 1/4", you wont get the nice idle flare-up to 1500 rpm's at start-up, and it may stall at stop signs. The conditions needed to trigger that relearn are to drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. That is the most complicated relearn requirement, but when people aren't aware of it, I have read where they have replaced all kinds of unneeded parts and the problem is still there.
Monday, September 19th, 2016 AT 12:02 AM