Solved- Updated: Still Need help- battery alternator alarm

2007 Double Cab 98k miles 4.0L prerunner.

Never any problems from this truck, until yesterday i was just driving down the road and it cut off in the middle of the road. Had to get it jumped and i drove to autozone where they said the battery was too dead to test. They took battery out & put it on charger for hour and a half, and then tested again & said it was 100% dead, so they gave me a new one under warranty (i had just replaced it a 18 months or so ago).

Put new battery in, and drove home fine.

Drove to work this morning and everything was fine, but on my way home from work truck cut off again. I got a jump but truck would not even stay running long enough to drive down the road. I ended up taking the new but obviously dead battery back to autozone where they said yes it is dead, but it's probably your alternator that is the problem (which happens to be only abuout 2 years old). So they charged the new battery up and I put it back in the truck, drove truck home, took out old alternator, took back to autozone and swapped out for new alternator. Came home put new alternator on, started truck and now my alarm is going off (usually after i connect the battery i can hit the OFF button on the fob and it will go off) but the alarm literally will not disarm.

The battery Light on the dash is on.

I drive truck back to Autozone and they said it's possible the old alternator fried that new battery, so they were going to swap the battery one more time and if the problem persists they will consider it an electrical issue and I am on my own.

Put new battery in (so now truck has new battery & new alternator) crank up truck, battery light remains on, alarm still will not disarm, gauges going crazy, ABS & traction control lights on, radio & AC intermittently working, etc.

Alarm still will not disarm. I have disconnected the battery and THEN turned on the lights to drain the system & computer 100%, then left sitting for 15 mins, come baackk reconnected battery...alarm starts going off, cant' get it to disarm with fob (have 2 fobs tried them both). Battery light still on the dash, & other lights blinking & going crazy.

Hoping i havent fried something electronically, ECU, etc.

Has anyone ever experienced this and can you offer any help or suggestions? Thanks.

 

I’d get rid of the autozone alternator. Being a previous Toyota mechanic. Toyota’s just do not like aftermarket alternators that’s why they just don’t last. Once that’s done start trouble shooting if it persists.

 

Thanks. How do i get the damn horn to stop honking? Like i said every time i hook up the battery, honks & stays armed and i cannot get it to disarm w/ key fob. I am pretry sure i also tried manually inserting the key in the door to disable alarm with no luck.

I read somewhere that "Toyota's" can be disarmed by turning ignition on & off 5 times in a row. Anyone know of this works on tacomas?

 

@gotoman1969

Being that you were a former toyota mechanic, if i take my truck to the local toyota dealership tomorrow, are they going to ask me whether i want a new vs reman alternator? And if so, which one would you recomend?

Thanks

 

There may be some useful info here:
https://www.tacomaworld.com/threads/alarm-broken-after-battery-change.179695/
https://itstillruns.com/disable-factory-toyota-alarm-7440586.html
https://www.yourmechanic.com/article/how-to-reset-a-car-alarm-by-samson-dikeman

Added comment: when battery is replaced, always check charging system after replacing a battery to determine if original battery died due to faulty alternator. A cheap voltage reader in one of the power ports will alert you to most common alternator failures before it kills a battery.

 

Go with new not reman.

 

Thanks guys: Update with more info.

This morning i went to Toyota dealership as I was just going to bite the bullet and get a new OEM alternator. However they only could get remans (not possible to even order new) and the reman wouldn't get here till Tuesday and was going to be $380.

So i went back to Autozone where I swapped the new alternator with another new alternator, this time upgrading from 100A to 130A.

Installed it and everything was fine for about 10 seconds. Battery light was off, the voltage was showong 14.4 across the battery posts. Then it immediately started going haywire again, voltage dropped to 12.3V, guages started going wonky, lights came on dash again (including battery light). So i drove to Autozone again where they tested and it showed "bad voltage regulator".

The thing is, the voltage regulator is part of the alternator.

So now i have put 2 brand new alternators in, but both have immediately gone bad.

I am beginning to think there is perpahs a short or loose wire or something causing the voltagae regulators to spike or pop immediately.

I took it to Toyota dealership & left it with them. Hopefully someone can test the resistance of the wires or something along those lines.

Anyone have any thoughts with all of this additional info?

What could be causing the voltage regulators to go bad?

Thanks again.

 

I did check the ground wire where it connects to fender, and also ground where connects to block above oil pan. All tight. Also positive was tight where connects to fuse box near battery.

Im at a loss.

On a positive note i did get the alarm to disarm. (Now cant get it to re-arm now, ha!) Only one thing at a time though.

 

Just sent out a message to a Toyota master mechanic as to his thoughts.

 

Thanks @gotoman1969 very helpful

 

He said have them check the wire harness close to the battery 1-2 feet. Look for any area we’re the loom may show corrosion. If so open up loom and look at wires very closely. Usually a power wire issue. Good luck. Hope they may give them a place to start.

 

https://www.tacomaworld.com/threads/battery-light.144814/#post-18685899

 

Check for continuity at the alt connector and battery to rule out a wiring issue along with fuses under the hood. Sometimes those wires at the connector gets crimped over time.

 

Thanks guys this is helpful.

 

My first thought would be ground but for a ground to unexpectantly fail is odd. First and foremost is make sure your battery terminals are sparkling clean and tight. Check continuity from the alt plug to the fuse block. There should be 2 fuses at the under hood fuse block that connects to between the alt and battery. One is the 140amp fuse and another is a standard 7.5 amp. Both are labeled on your fuse block cover. The other wires from the alt connector goes to ECM, BCM and to the inside fuse block. Check the inside fuses labeled 7.5 gauge, and both IG1 fuses. The only other items that I would lastly suspect but possible is either the BCM or ECM.

 

Yea I would check ALL the fuses .

 

Thanks guys. Most recent update.

Truck is currently @ Toyota dealership. Technician called me this morning and after going through everything with him, he still suspects that this is just an aftermarket alternator issue and beleives a new (or reman) Toyota alternator will fix the issue.

I'm not 100% sold, but that is why I left it with them as opposed to just buying the part & putting it on myself, because if the new Toyota alternator "goes bad" immediately, then at least it's on them at that point to find & fix the problem.

It's going to be $600 ($400 alternator + $200 labor) for them to put a reman alternator on there, but i feel like i do not have any other choice as this is sort of paying an "insurance policy" that if this doesnt fix it I wont have to come out of pocket for the next one they put on after finding the actual problem (whatever it may be).

And of course there's a chance that this new Toyota reman resolves the issue and i will have paid an extra $200 for them to install, as an insurance policy essentially.

I guess we will find out tomorrow when the new alternator is installed.

I'll update the thread either way.

Thanks for the help.

 

So, if the wiring is shorted and burns out the new alt; will Toyota replace it at no additional cost? If yes, I would want an assurance of this, maybe in writing.

 

Alright guys- the update everyone has been waiting for.

Toyota put a new (reman) alternator on and it seems to have solved the issue.

Will keep an eye on it, obviously, but so far so good.

So $600 later and all is well.

Thanks for the help.