For those who can't stand "not knowing", the outcome was...I ordered a remanufactured computer from "that place" in Florida. Took four days to arrive, it was the wrong part (wrong wiring harness, box, etc). They shipped the correct item on "next day" air, which took from Monday til today to arrive. (This is day 15 of the whole mess).

Popped in new computer, truck started right up, got 18 miles down the road toward home and all power died. Totally. No radio, no blower, no gauges, etc.

Irately called that place in Florida and demanded a third computer which is being shipped. Called dealership, and a new OEM computer is back ordered indefinitely here.

Got the truck towed to the house, took out the 'new' computer and put the original box in it, it spun but wouldn't fire, like before so I'm certain that box is bad.

Put the battery on charger, the truck has cranked every time I've tried with the new box in it, but I don't trust it since it left me on the road earlier this morning. Can those PCMs be half bad?

The only other notation on the bill was that "#2 cylinder has 70 pounds compression, probably exhaust valve", whatever that means, but it's not computer related. Just makes it run a bit rougher, as I understand it.

When it left the shop, the mechanic noted that the alternator gauge didn't appear to be reading anything, although you could hear the alternator whine. Apparently, I was running on total battery and it just crapped out when it ran the battery down?

For whatever reason, it worked fine after I disconnected and reconnected every wiring harness, etc.

My insurance agent has set aside a slush fund to pay my wrecker bills. Best two bucks a month I ever spent was on roadside assistance.

 

Ok, we seem to have what some engineer types call a 'cascade failure.' The PCM appears to be bad. The engine runs roughly, and the alternator voltage is steady about 9-10 volts.

In addition to this, the battery is five years old and won't take a charge no matter how long I leave it on the charger.

Can a bad PCM screw up the charging system, ie, 'mimic' an alternator failure, etc? As I understand it, and it may be incorrect, everything proceeds from the PCM outward to the engine.

Public transportation has thus far been wonderful...

 

The voltage regulator is an internal component of the PCM, so yes it can definitely affect the charging system. At 5 years old it is a good idea to just replace the battery anyway. The electrical system in a Dakota is super sensitive to low voltage. Even the slightest fluctuation or decrease in voltage can cause the truck to run very poorly or not at all.

If you only have 9 volts at the battery, the voltage regulator is probably shot. And I would guess the voltage regulator is shot due to the poor condition of the battery. The battery can not accept a charge and it caused undue strain on the voltage regulator. This whole problem almost sounds to me like it could also be that the alternator could be bad, which can also freak out the voltage regulator and the battery is/was not receiving a sufficient charge as a result.

If this were my truck, I would replace the battery, the alternator and the PCM, in that order. Sorry to hear about the problems with the new PCM, I guess sometimes you just get a bad part, but you have had more than your share of trouble with this problem.

Let us know how it turns out or if you need more help.

Jimmy

 

Computer #3 arrived today. It was shipped 2nd day air from Florida and it looked like it had been drop-kicked off the truck, box ripped open, etc. I hope they're hardier than they look.

In the mean time, I bought a new battery and installed it, did a quick and dirty voltage check. Right outta the box, it was 12.83V.

Hooked up everything, new computer, battery, etc, cranked it up, got no error codes, but the voltage across the battery was 12.2. When I turned on lights, radio, heater, etc, it dropped to 11.67 before I shut it down. This whole process took less than a minute, so I doubt there was much damage in either direction.

Unhooked the battery cables, voltage was 12.71, so just that one minute cost me a bit of battery life.

New alternator tomorrow, I guess, eh? Come full circle to get back to the original problem after all.

Thanks to all who have helped. Quite a learning process and I cleaned out the garage while waiting for the UPS guy...

 

Sounds like the alternator is bad. It also sounds like the truck is/was running on battery power alone. At idle with a good battery, good alternator and a good voltage regulator you should have 13.5 to about 14.2 volts across the positive and negative battery terminals. Anything less indicates a charging system problem somewhere.

With the air conditioner and high beam headlights on with the engine idling the voltage should stay in the same range, between 13.5 and 14.2. And you should still have 13.5 to 14.0 or 14.2 volts with the AC and high beams on at 2000 RPM.

Autozone and Advance will test the alternator for you for free. But the voltage you have now really points to a bad alternator. Or maybe the alternator is bad and causing the voltage regulator to not work like it should. And it could also be a possibility the bad alternator is the reason why two new-rebuilt PCM's didn't work.

Also check all the grounds. There is one on the engine block behind the bypass hose at the water pump, another one on the block behind the ignition coil, one in the driver's side inner fenderwell and one on the frame behind the left front tire. It might help to remove the bolts and hit the connections and the bolts with a wire brush and some solvent. Bad grounds can really freak out the alternator and PCM/voltage regulator, and the rest of the electrical system. Also when you remove the alternator, check and clean the cable connections there too.

I hope the new alternator finally solves the problem for you. Let us know what happens or if you need more help.

Jimmy

 

Well, I pulled the alternator bright and early this morning and took it to O'Reilly. Had the guy repeat the test five times and it passed all five times.

I'm officially out of ideas and back to "WTF". New battery, new-reman computer (what're the odds that they sent me three crap computers?), new plugs, new fuel pump (not that makes any diff...that really was bad), what the hell else can generate electricity in the damn thing?

I'm seriously ready to overinsure and set it on fire.

 

Wow. WTF doesn't even begin to cover it. If you ask me, I think at this point the best thing to do would be to get the truck to a Dodge dealer and have them scan it with the DRB-3 scan tool. It's the only way to really check all the electronic systems on the truck and it is the only way to accurately test the PCM and all the other control modules on the truck. Even if they charge you a half hour or maybe an hour's labor time for the diagnosis, it would still be well worth it to find out what really is wrong with the truck.

I just wonder if you don't have a problem with the Central Timer Module. The CTM does work with the PCM. My shop manual says it monitors voltage for the PCM. I can't tell if the CTM actually supplies power to the PCM though. Manual just says it works with messages from the PCM for system voltage. I do know that CTM failure is a fairly common problem on Dakota's. A new CTM costs around $200.00 at the dealer but it is a part you can replace yourself. If you have the factory keyless entry system you have to program your remote control fobs to the new CTM. The dealer does that with the DRB tool, but there was a post on here not long ago about how to program it without a DRB.

I guess you can cross that bridge when you get to it. I think the dealer should check the truck for you. That's the only way to find out what is wrong.

Good luck.

Jimmy

 

Well, since I have the luxury of having an auto parts store a quarter mile away, I bought a remanufactured alternator and buttoned it all up, after checking and cleaning every ground on the truck.

Same story. Voltage on the new battery is 12.83V, turn the engine on and load it up, it drops to 12.00 pretty fast and that's where I shut it down.

Off to the dealer it goes on Monday.

 

Since I can't help tinkering with stuff, and since the dealership is closed til Monday, I decided to measure the voltage at the back of the alternator. With the engine running, I put the red lead on the big lug on the back and the black one on the ground where the negative battery cable terminates. Not sure if it means a damn thing at all, but it read 32 volts.

If this is a valid measurement (IF), and the battery reads 12 volts regardless, where's the other 20 V going?

 

I never heard of an alternator charging 32 volts. At idle most alternators on most vehicles will produce about 30 to 32 amps of current with no accessories on. The most voltage at idle from any alternator should be no more than 15 volts. Was your meter set for Amperage or Voltage?

Jimmy