Help!? Dash restarts when brake barely applied?

Whole dash restarts and engine almost stalls when brake is barely applied. Happens when in park or drive and also infrequent. Ideas on what's happening here? 2018 trd premium.

 

My first question would be if you have any aftermarket electronics installed. Specifically tail lights or anything that would react to the brake pedal. That's where I'd look first

 

Agree^,

Seems like someone else posted these symptoms/situation a long time ago. Don’t remember the outcome. Might not hurt to get the battery load tested.

 

^Agree. And if the battery is bad - replace. If / when the battery is replaced, start the truck and wait a couple of minutes, put a voltmeter on the positive and negative battery terminals. A healthy alternator will show a voltage of just over 14 volts across the battery terminals. After engine start, and after the battery is recharged, the battery becomes an accumulator, or reservoir for demand on the electrical system.

 

The brake lights are aftermarket 1off's but they have the proper resistors on them.

 

For troubleshooting purposes, you may want to inspect those resistors. If one of them is touching bare metal, that would be a direct short circuit. A direct short will hurt your electrical system, such as the battery and alternator. Really though, it should blow the fuse. But from your video, you have a pretty good electrical problem going.

 

As others have posted, you could/should have the battery checked. I feel that once started the alternator (if good) should keep the battery in good working order though. Initial startup would point to a battery issue for me.

The fact you have aftermarket tail lights would be my red flag. They may have worked flawlessly for 40k miles but nothing screams "look at me" with an electrical issue when brakes are touched like the brake lights.

Do you have the originals? Easy to diagnose by swapping out to see if issue persists.

 

Agree with @FN2187 best to put the original tail lights back on and see if the problem goes away. I would still have the battery tested though.

 

Think they will void my power train warranty with aftermarket tail lights/ head lights?

 

Warranty is only voided if the aftermarket part is determined to be the issue. So if your taillights somehow cause damage to your power train (or their electronics) then, Toyota will not repair the issue under warranty.

 

Unfortunately, we’ve seen this movie before. Newer vehicles just don’t respond well to aftermarket electrical components.

Agree with the other posts, try putting the electrical system back to stock and see what happens.

Good luck.

 

Same thing is happening to my 4runner. No mods, all stock. We have had issues with the brake lights constantly going out. Maybe ill start there bc no one can seem to find the problem.

 

I think you should also look at this from a different angle. The first poster mentioned "electronics" and everyone has jumped onto that train with electrical related suggestions. Now, I'm about the most clueless person concerning all things mechanical and electrical, but looking at this issue systematically, I don't think the dash lights will restart as a result of a short somewhere and cause the engine to stall. But then again it may have everything to do with it (remember, Im clueless). But what if it's the engine stalling first, and in turn causing the dash light to start over? What if the problem is something mechanical? It makes sense to me that if the engine dies or starts to die, it's possible voltage or current (see, I'm clueless) would be cut off. The alternator is not sending a charge when engine isn't running so as a result, the dash lights cycle through again.

Failing brake booster. This will cause a vacuum leak effecting the engine.
Maybe check for a vacuum leak causing engine stall in the intake manifold or brake booster?
Maybe check for loose cable in the alternator - engine circuit?
Idle air control valve?
Check throttle body or idle air control valve (issues with these are sporadic at first)
Dirty mass air flow sensor?

 

OP hasn't been seen for a year, so no news on the fix, unfortunately.

 

Would be nice if @Mesot4r posted an update but they don't even come up as an @ member of the forum

 

It looks like there's a fresh report from a new member here: https://www.4runners.com/threads/help-dash-restarts-when-brake-barely-applied.28455/#post-514325

 

Isn't that post #13 above?

 

Oops, should be #12, although it gives fewer details.