All lights on help please

Hey I'm new here I have a 2012 tundra sr5 all my lights come on 4hi lo flashing speedometer drops.to zero voltage meter read 19v doesn't effect my drivabilility dealer said they want to replace the entire wiring harness... there's no way anyone else.have this issue? Also it'll go rightback to normal randomly too

 

First steps I’d take are to load test the battery, make sure the clamps are clean, tight, and completely free of any corrosion. Then use a voltmeter to measure battery voltage while the engine is running to see if it matches the 19v reading on the dash.

 

This.

then report back.

It’s possible the voltage regulator on the alternator has shit the bed.

 

See that's what is hard to do as it is intermittent not constant that's my main issue I gotta drive around with my voltmeter and hop out as soon as it happens lol maybe just replace alternator? I can post a video but it keeps saying not right extension or something like that

 

Okay this morning on way to work all lights came on turned off than low voltage instead of high got out checked voltage is only 12 with car on I think you may be right... alternator

 

If it is really running with 19V you will be having problems soon.

The fact it dropped down to below 12V and sometimes is up at 19V really leads to think the alternator is going crazy.

 

Okay update I replaced the alternator just now still 12.25 volts at idle isn't that low should.be closer to 14 right...truck won't let me disconnect alternator leads and stay on maybe the batt idk at this point

 

Voltage when running should be 13.5-14v across the battery terminals. Verify your meter is set on the correct range and DC volts.

 

Yes it's set correct I read 12.25 volts when at idle after changing the alternator

 

Are the warning lights still present?

 

No lights on as of right now I would have to drive to see if it goes wacky again

 

Make sure the 7.5A LH-IG fuse is good. It powers the voltage regulator when key comes on. It’s in the interior fuse box, drivers side under dash.

Also a 5A Alt-S fuse in the engine fuse box. Would check it as well

 

Oh fire I'll check that QST thing in the morning and post what I find thanks

 

Sorry took so long finally got to it fuses are good this is crazy is there is no way it's a bad battery right I can't keep truck on and take leads off to see if it pumps.out correct voltage truck turns off when disconnect battery

 

Id try a new battery or swap with someone for a test drive and see what happens. Nothing to lose.

 

Yah true can always return but really hope ill try it tm doesn't make sense to be anything else

 

Update on the truck voltage still low at 11.87 at idle so lost now

 

Are you good with a voltmeter. I can give you some other places to check for voltage to see if a system is on (12v) or off (0v)

 

Did you take your battery to a shop to have the load test run? You never mentioned after a few people told you to do that. You might have a bad cell or 2 ...the last few batteries I had in my other cars had bad cells (a Bosch and an AC Delco) and I was able to get new batteries under warranty. It happens more often than you'd think. You also might consider that a rat got into some of your wiring and chewed through something related to your issues. You mentioned that the dealer told you to get a new wire harness. Did they state why they think that other than your symptoms? Have an independent mechanic who specializes in Toyota confirm the wire harness repair the dealer told you. We have an epidemic of Toyotas having destroyed wires from rats around where I live so it's something to consider in your case if you've ruled out the obvious other things.

 

I am good with a voltmeter... also I put new battery in.... the tech thinks new harness because his computer said a wire on the passenger side had high resistance aj4 I believe it was but if the alternator isn't pumping out volts what that have to do with it?

 

Look on the back of the alternator assembly for this plug. You need to measure voltage on Pin1 (Black/Yellow wire), then check Pin2 (Green/Yellow wire)
Positive lead on the pin, negative lead to ground at the battery.

You should get 12v Pin1 (Black/Yellow wire) all the time. Its wired directly to the battery. On Pin2 (Green/Yellow wire) you will only get 12V with ignition (key) on. I would check with just the key on and the check again with the truck started and running.

 

Aight will do thank u hopefully I can get to it today with work lol

 

So this is funny went to go check that plug with voltmeter and forgot to plug it back in when I changed it out so the new alternator did fix the problem... thanks for the help BTW. Now gotta fix the nuts that broke free in the frame from the sway bar fml

 

Cool. FYI the wire that goes to 12v with the key on in that plug is the on that enables the voltage regulator. It is powered through the fuse I listed above. Seems your old voltage regulator was bad. Reasons you saw 19v at one point which is not good for the electronics in the truck.

 

Yah I was super worried about if and when toyota dealer told me that wasn't the problem and wanted me to spend 8k on a full harness I was like nah sounds wrong imagine they did that would.have still had the problem that. What 8 k plus labor like yo