Fixing an Amperage Fluctuation in my ’99 Dakota

This is more informational than anything else, so it won’t fit into any categories I have on my blog. So be it, that’s fine.

Over the last few days, my electrical current problems have become a bit worse. Most recently, I returned from a trip in Prescott hiking. I pulled into the driveway and turned off the truck. I went to open the door, and my cab light didn’t come on. I checked the dash switch for it and it should have been on. No headlights, no stereo. Not even a turn over with the ignition. I fuddled around with the ignition a bit more, and everything came back on. I had grown pretty certain that my alternator was acting up again, and was breaking the circuit. Perhaps fiddling with the ignition barely pushed it into a good position to allow current to resume. Didn’t think much of it.

Monday passed and nothing happened until I got home again. I had noticed my amperage creeping up near 15 on the dash. But it was staying steady. I got home, and the truck killed itself again. Sat back in the seat, fiddled around with the ignition again, and eventually everything came back on and worked. This was too frequent; I thought I was gonna have to get the alternator looked at. It had whined earlier in the year, when it was really cold. Being this close to my trip to Germany, I didn’t want to spend money on the truck.

So I drive to Scottsdale today to go to work, and I pulled into the parking lot and shut off the truck to find the same thing happen again. I get out, about ready to just call it quits on the truck when everything comes back on by itself. Stereo beeps, dome light comes on.

…wait a minute. I didn’t mess with the ignition. Did my weight shifting around in the truck cause something loose to come back together? I didn’t have time to think on it, so I went to work. And then, I had an educated guess– or as my friend likes to call it, a “headache with pictures.”

The amplifier for my subwoofers sits underneath my driver seat. It had shorted out before (causing a fuse to pop) but only once. So my thought was this: shifting around in my seat was moving the amplifier about. It’d cause a partial ground out on the entire electrical system, which would cause the alternator to work overtime. That’s why my amp rating was sitting at about 15 to 15.5. And then when the truck shut off, the alternator was no longer supplying additional power, and the amp ground it out until I moved in the seat.

So I decided I’d try that next. When I got out of work, I pulled the in-line fuse I have as a backup to the amplifier, and I’d see if that fixed the issue.

No dice. In fact, things got worse. My amperage was increasing or decreasing based on the revs I was giving the engine. In particular, it was now starting to approach almost 16 before stopping. My mind immediately went back to the alternator. Over the course of the drive, the amps came down a bit in range, going from 14 at idle to around 15 or so. It had to be my alternator. I got home, and expected the truck to shut completely off when I killed the ignition, and sure enough it did. I got straight out of it, and was about to close the door again when the stereo beeped, and the dome light came on again. Hop in, the truck starts.

A few thoughts begin to form. The most prevalent of them all, is that this blackout period is almost exactly the same each time. And that means…

…the ECU was rebooting before bringing everything back up.

The ECU is the Electronic Control Unit. It is sometimes referred to as the ECM (Electronic Control Module). I’ve had funky issues with it before, where it wouldn’t keep the truck at idle and it’d stall out after startup, and it’d regain composure and keep it after I revved for a bit. That was in the first year I owned it. I had been given a performance chip by my brother, but it had been on since last summer, and this issue started creeping up only recently. So I began to think that it fell back to the original ECU.

So, I went down to my truck after it had cooled down a bit. I disconnected the negative post on the battery, and unseated the entire cable that leads to the ECU– it’s a cable that feeds truck information to the unit. I let it sit for about two minutes to let all of the juice drain out of the system altogether. Reseated the cable, reseated the terminal, started up the truck.

14A, on the dot. Drove it around, and it stayed that way. Even at 65 mph.

I had no idea the ECU could directly control the current on these earlier model trucks. I learned something today. And I am glad I thought this through, too. I was not ready to pay someone to look at it to find it wasn’t an issue after they disconnected the battery as one of the steps to checking the ECU.

Hope this finds other Dodge owners who have a similar issue. Always try resetting your truck like I did.

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