Mechanics

DODGE DURANGO BATTERY PROBLEM

2000 Dodge Durango • 105,000 miles

My 2000 Dodge Durango 4x4 was recently transported from North Carolina to Oregon as part of a job relocation. The week before I had it shipped, I had a garage inspect the vehicle. Other than replacing the worn battery terminals, everything else checked out. The car ran fine for a week, then it was loaded on a transport truck and driven away. When it arrived in Oregon 12 days later and was unloaded from the transport truck, I instantly got a dashboard warning "check gauges" and an airbag alarm. The dash gauge out of spec was the battery gauge, which indicated an overcharge condition (18v). I took it to a dealership, that identified the problem as a faulty powertrain control module. I had it replaced, then asked them what could have caused such a condition and could I link it to the recent transport. They said the only thing they could think of would be if, during transport, the battery had died (i.E, a dome light left on) and they had tried to charge it attaching the + and - wrong. They couldn't say this had actually occurred, so they had no way of determining whether the PCM was caused by anything the transport companies might have done. Do you know if a PCM could fail during transport of a vehicle, and if that failure was due to mishandling by the transport company? Thanks.
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Guest
November 30, 2012.




Very doubtful they did anything wrong. To be overcharging is the fault of the voltage regulator, (or the wire going to it is grounded), and the regulator lives inside the Engine Computer. That circuit causes very little trouble.

Connecting jumper cables backward can do a lot of damage, and we read about it here every day, but it is unlikely the only problem would be with the voltage regulator circuitry. That is the last thing in the computer that would be hit. The alternator is the first thing because they all have at least six diodes which are one-way valves for electricity. They are in the circuit backward so they prevent the battery from discharging when the engine is off. Connecting jumper cables backward "forward biases" those diodes which turns them on, and in effect, turns them into a piece of wire. There will be nothing to limit current to safe level so those diodes will short instantly or a large fuse going to it will blow. On older vehicles that fuse was a special wire in the harness that was thinner to make it the weak link in the chain, and it had a special insulation that would not melt or burn. On newer vehicles that is usually a large fuse bolted into the under-hood fuse box.

Computers and the radio have diodes inside them also to prevent damage from reverse polarity. Those diodes are between the power and ground wires but are also installed backward. They don't do anything when the battery is connected properly. When the battery cables are reversed, those diodes turn on and draw high current forcing the respective fuses to blow. That saves the computer.

Your vehicle has a Central Timer Module that turns off unused lights after 15 minutes so the battery shouldn't have run down. Due to all the computer memory circuits, there is a constant small drain that will run it down over time but 12 days shouldn't have done it. Unless the manufacturer specifies differently, 35 milliamps, (.035 amps), is the accepted standard value, and at that rate, Chrysler says a good battery will crank the engine well enough to start after sitting for three weeks. If your battery is older, it might not hold out for 12 days, but if a jump-start was needed, I suspect you would see multiple other problems if the cables were reversed.

Caradiodoc
Nov 30, 2012.


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