Mystery: Battery light while braking and cylinder misfires

Hello!

I've run into an odd situation and I'm not sure how to proceed. Lately I've been getting an intermittent battery light on my dash. It doesn't always happen, but when it does it's when I am accelerating or braking. It doesn't have to be aggressive acceleration either; simply going up the parking garage at my apartment complex is enough to turn the light on. When I take my foot off the accelerator the light turns off. Another thing I noticed is that I can leave the truck in park and hit the accelerator but not trigger the light at all. This leads me to believe it might be a poor connection to the battery or a loose connection somewhere. There was quite a bit of corrosion on the battery terminals, so I rubbed it down with sand paper and ensured the connection was good. Didn't make a difference, so I'm back to thinking it's a lose cable.

The other issue I recently ran into is a blinking engine light. This only happens when I'm accelerating aggressively. I checked with my OBDII reader and pulled these pending codes:
P0300 - Random/Multiple cylinder misfire detected
P0301 - Cylinder 1 misfire detected
P0306 - Cylinder 6 misfire detected

I wonder if this is related to the intermittent battery light I'm experiencing. I'm not sure if it's related, but I also heard a concerning noise in the engine compartment a week or so ago. It sounded like a cable or something got caught in the belts and whipped around under the hood a few times. I pulled over immediately and looked around but couldn't identify anything out of place.

Hopefully someone can help me connect the dots. I'll continue troubleshooting on my own and will post back if I find out what the culprit is. If anyone has gone through something similar I'd love to hear what your solution was.

Thank you,
Tom

 

Check the voltage at the battery when at idle. It should be over 14 volts. With some accessories on (headlights, blower fan) it should remain above 13 volts. If it drops below 13 volts then the alternator isn't putting out enough current.

The battery warning light is wired to the alternator wiring, not the battery, so the battery terminal corrosion probably didn't have anything to do with it.

The misfiring could be from the voltage dropping.

You could also have the alternator belt slipping causing the voltage drop and corresponding warning light. If the belt drives the water pump also, you need to check that both the alternator and water pump spin freely. Take the belt off and spin them to make sure the bearings aren't binding. Check that the belt isn't too loose also.

 

get your battery load tested and alternator checked...it could just be a bad cell in your battery. If its your alternator going bad it could drain the battery and then you'll be stuck somewhere.