First Battery Light, Now ABS and Brake light only, Battery slowly dying

-I can't find my code reader, but think obvious next step is to read codes for #2
-Just curious if anyone has any ideas about the sequence of events and what's most likely next step(s)

-2008 Toyota Tacoma PreRunner RWD, 4cyl

Problem #1
I was driving yesterday and noticed the battery light start to come on and off. When slowing down (braking) or hitting bumps it would go away for up to 4 seconds, but always came back on and was mostly on (98% of the time).

Notes
-When I got home I checked battery terminals, wires around alternator (removed covering to check for corrosion), etc. Everything looked ok.
-I test battery with multimeter and didn't see a DC voltage difference when the car was running, so I made a best guess that replacing alternator would work.

-So I got a new alternator today and swapped out hoping battery light would turn off.
-Battery light did NOT turn off initially, but did after I start driving a little while later and brake a few times. That light is now off completely.
-Concern: even with new alternator, the battery reads the same voltage while the car is running or off.

Problem #2
So I decide to run a few errands close to home. In between stop number 2 and 3 I start the car and notice it's starting to struggle a bit on start. I notice that now my ABS and Brake light are on solid. But the battery light is still completely off.

Notes
-I made it back home and go through a few more off/on starts in the driveway intentionally trying to waste the battery.
-The vehicle is definitely starting to struggle a bit on starts now, however once started it does seem to run pretty smooth.
-When back at home, I checked voltage and still had 11.5V, but then after a few more stop/start am now down to about ~9.5v when running or stopped... and Battery light is still completely off
-As mentioned above, I think obvious next step is to read code and see what's going on with that (If I can ever find it... we're in the process of moving into a new place)

Recent Events (Possible root causes?)
1) Two month ago I had a mechanic replace the engine cover gasket that was leaking oil. Looks like this involved removing most of the wiring harness... but again that was two months ago.
2) Last week, it was dark and I hit a curb really hard on the right front wheel. I pulled off and check for any damage but hadn't seen any. No flat tire, no alerts, etc. Actually very normal driving for about 3-5 days (albeit pretty limited driving (~15 miles total) due to the covid. Just a few nearby errands during the week, etc).

I've been researching the forum here and elsewhere and ...
-I have never jump the car backwards like many with similar problem say they have done.
-When installing alternator, I removed negative battery terminal
-I've been combing over the wiring harness looking for any defects that could have been caused from the repair 2 months ago and have not found any yet.
-I've visually checked inside wall of the wheel I hit the curb with last week and don't see any bends. I also don't see any physical damage to wheel speed sensor or wire to that sensor.
-While I don't really know how to check everywhere for loose grounds, I'm combing over the entire frame and checking all that I can find. Not sure if there is logical process to apply to validating loose grounds.
-I also cleaned the terminals to the batteries and retightened all connections
-I also checked Alternator fuse in fuse box and it looks good.

General Questions I'm Asking Myself:
-Since battery light would go off usually while braking and now Brake/ABS light is ON, it seems possible hitting the curb last week did some kind of damage. But why in the hell would that keep battery from charging?
-If car was fine when battery light was on, but now I have noticeably low voltage and struggle starting (probably only a few starts left) Why isn't battery light on now?
-Did replacing the alternator actually do anything to help clear battery light or since voltage is still steady whether stopped or started, was that not necessary? Why isn't voltage higher when started with the new alternator and all wires clean with no visible corrosion or splits ?!?!?

Next Steps
1) I definitely need to find the code reader and see what it's throwing, but that could take days and I don't trust the car enough to drive to the auto store.
2) I'm thinking seriously about getting a new battery tomorrow. My current battery is around three maybe 3.5 years old, so I think I still have a year on it, but would this be a waste at this junction?
3) Any other ideas for next step, tests to try, etc?

 

Did you check the wheel speed sensor on that wheel? The impact might have messed it up and or something hit it or the wiring...

 

Yes, visually checked it out and looks ok:

-I've visually checked inside wall of the wheel I hit the curb with last week and don't see any bends. I also don't see any physical damage to wheel speed sensor or wire to that sensor.

Update: I found my code reader (ODBLink MX) and there are no error codes showing up.

 

Low voltage will make all kinds of problems. You need to focus on why the charging system isn’t working. Plenty of people have had problems with POS box store rebuilt alternators.

 

Can your OBD reader display batt voltage, while the engine is running?

 

Yes. Battery voltage is the same running as not running. I was at 11-12v but am now at 9.5v running or not running.

Is there a way to test the new alternator on the alternator leads? That's fine if others have had problems with these but I didn't see any other options from the auto stores in DFW and would hate to replace again if it's actually ok. Any way to test that other than check into battery voltage while running?

 

Have you checked to see if the battery terminals are bolted tight yet? As they could be loose.

 

That battery voltage is way too low. You should be around 12v with the truck on but not running. Idling it should be somewhere around 14-14.5 volts. Driving down the hwy anywhere between 13-14 volts.

I rarely get more than 3 years our of a battery, but Montana is a harsh place.

 

Yes
-I also cleaned the terminals to the batteries and retightened all connections


My next step is probably a new battery but I don't understand why I wouldn't have higher voltage when running. If battery was bad and alternator was good, shouldn't I still see an increase in voltage on the battery when running?

 

A voltmeter can test the positive top lead off of the alternator. Has a Grey or brown plastic cover. That could also be loose.

Check there as well.

You can have your battery tested, but at its age, it may very well be bad.

Then the alternator is definitely the next culprit.

 

Multimeter first.

 

I would also check all fuses under dash with multimeter or test light . My usual simple 1st step when trouble shooting electrical .

 

So I did just disconnect the main connector on the alternator (where I should have 13-14v), started the car and checked voltage from that stud to bolt in the car chasis and I only have 1 v. I'm going to try to get the 'new' alternator swapped out and maybe grab a battery and see what happens next.

 

All I do is touch the battery engine off. I’m looking for about 12.7 (?). Maybe 12.9.

then I start the car and repeat. I look for mid 13.

I want a Fluke meter with the min/max feature so I can load test the battery. It’s on my Christmas wish list I secretly send my wife every year. So far, nothing.

 

With an AC/DC amp probe. Clamp around the wire, 1mv=1 amp....

 

A bad battery
can toast an alternator

 

Update: Looks like @Muddinfun was on to something. I took the alternator back to the store I purchased at tonight, we put into their test machine and it failed all tests. They should have another one tomorrow or Monday and we're going to test it in store first before I take it. Also, thanks for the tip, @Decapster --- I didn't know a bad battery could do this to an alternator. Although I think my battery is ok, I will probably go forward with the plan to swap the battery at the same time just in case it was my battery frying the alternators all of a sudden.

Additional Note: For testing the Alternator and Battery I found this Youtube video to have the best technical info of any of the ones I was going through. This helped me confirm that I had been testing correctly and gave me that added confidence to go through the hassle of removing 'new' alternator from truck and taking back to store to test there:

https://www.youtube.com/watch?v=ab5Kk6JkbsI&vl=en

 

I had my battery drop a cell last year. Everything was fine driving into town, till I parked it at a store and got back in 20 mins later to a dead battery. Jumped it with much difficulty, got home(~30min drive), and was dead again as soon as i shut it off and tried restarting, multimeter read 4ish volts. Managed to jump/limp it to the Yota dealer the next morning (along with a symphony of dash lights and power completely cutting out every now and then; thankful its a stick and i was able to keep rolling with it) and they confirmed the battery was internally shorted. Luckily my charging system itself tested fine.

Upon reading further down the thread, looks like you got it figured out. Best of luck

 

And a bad alternator can toast a battery!

New battery.

 

Update:

I don't have this figured out yet.

Got replacement alternator and battery tonight and installed both.

Replacement alternator tested fine at store... I put in my truck WITH new battery (to rule out old battery as the problem).... Start vehicle and now Battery light is on.


I go to test voltage on the alternator and it's like it's not working.

Is there something in my truck here frying alternators? That's what it seems to be... I'll have to take this replacement back and have them test to be sure.

What could cause this? I guess I could trickle charge every night to get by... But woul d like to figure this out somehow