Brake lights flashing in extreme cold

Stopped by the Toyota dealership in Fairbanks on my way through. I described the probem. Their first question was "are you using the parking brake." I use it religiously. They said, stop using it unless parked on a hill, "they tend to do that in the cold."

Off course, as I use it out of habit, every time I got out the parking brake was on. I also found it interesting that as soon as I confirmed I was using the parking brake they asked "you driving a manual?"

Anyway, I figured if anyone would know the answer right off it would be the Fairbanks dealership. Glad I stopped in.

 

WTF? Parking brake? LOL.
If you're good with that, that's all that matters.

 

Well, if it stops doing it if I leave the parking brake off it is a good enough answer for me. course, if it is still doing it even with the parking brake off, than I will be looking for another answer. I will likely know by tomorrow morning.

It does not make sense how the parking brake would cause that. But the speed and confidence of the answer makes me think they have seen it before. I literally gave no more information than "brake lights are flashing in the morning if it is below about -4" and they had an answer.

 

I too, always use my parking brake and have never seen lights in those temps. Granted, I don't see those temp as often as you, but I back in to my driveway and would like to think I would have noticed.
So, if you confirm the parking brake explanation, you going to troubleshoot it or just stop using the parking brake?

 

The park brake doesn't activate the brake lamps in normal operation! How does it suddenly activate them with a temperature based pulse when cold?

Just out of curiosity I just checked my truck with the park brake applied, and running. No brake lights....

 

Parking brake does not affect brake lights.

 

My 3rd time to suggest putting the OE units back in and see what happens. You could have done that multiple times while messing with everything else.

And I call full septic tank on the dealership.

 

May be, through CAN...

 

It doesn't. I've taken a look, as well as @Speedfreak.

 

Dafuq?!

 

Well, we will not be back below 0 for a week or so, thus I'm unlikely to have an opportunity to check anything for a bit.

There are several reasons why I don't think it is the tail lights (I also was not at home, so could not have gone back to stock anyway, at least not without making a 3 hour round trip to buy bulbs at an auto parts store).
1. If it was the cold lowering resistance that caused this it should not stop with the engine bay warming up as most of the circuit to the tail remains frozen.
2. The stock 3rd brake light is doing it as well.
3. Short of applying a power source, the tail section cannot energize the circuit. No other lights are acting up, and if they where I would still have a problem outside of the Meso products. As blinkers, reverse lights, and tail lights do not alter the patter on the 3rd brake light on both the bed cap and the truck cab, the problem cannot be a power leak from the tail/reverse/blinker circuits. Plus, if this was the problem pulling the brake light relay would not stop it.
3. If the problem is the Meso tail lights/harness, than simply unplugging them would stop the flashing on the 3rd brake light. Funny that people will suggest going back to stock, but not simple disconnect the harness.
4. As bulbs and harness cannot close the circuit, even if the added resistance of the incandescent bulbs stops it, all I have done is mask the problem, not fixed it.

My opinion is that the after market tail lights are a distractor that in the absence of an answer people are latching on to. However, as at this point someone is going to blame Meso just because, I will flip back to stock next time it does it (to include unhooking the harness for the bed cap, as that makes as much sense as a culprit, as what many are blaming).

If the parking brake explanation checks out, I will probably say WTF and ignore the problem unless I get bored (well other than reinstalling stock tail configuration to confirm or invalidate what I think I know).

Correct, a parking brake should not turn on the brake lights. Conmen use that in insurance scames were they try to get people to rear end them. I am curious if applying the parking brake while moving activates the brake lights, I really don't think it will.

If parking brake and going back to stock don't make a change, I'll flash the ECU back to stock as well. Then take it to the dealership. I think the tune is more likely to be at fault than the Meso tail lights, but would really rather not flash the ECU if I can help it. Plus, as I will not flash it with the engine cold, I would have to wait for the next sub 0 night to find out if it did anything. Which is another reason to leave it for last.

 

From my extensive experience troubleshooting LED indicators lights and LED area lighting for outdoor High Voltage substation equipment, Generator installations, and aboard ships in the freezing cold:

LED lights have a few traits that can cause issues like you are seeing:

-Firstly LEDs will display flickering voltage, due to their sensitivity to any and all voltages, that you would otherwise not be able to see with an incandescent lamp. In very cold and/or dry conditions, the static in the air can cause discharges through LEDs and cause them to flash. A static charge may come from an adjacent cycling control circuit that may be pulsing/polling. These imposed/induced voltages can also bridge the gap to the LED circuit if conditions are wet and everything is damp. The good old normal incandescent lamps don’t light up fast enough to show these issues, so we remain blissfully unaware. This is usually a case of the LEDs showing you a phenomena that was always there, that doesn’t matter, but now you gotta think about it. Manufacturers figured this out and added components to many LED lights to prevent false indication, or flicker when the lights are “off”. I imagine Toyota OEM LEDs lights will not do this as they are surely aware of the issue. Aftermarket-who knows?

- Secondly, LED lights have ballasts/drivers that contain components whose properties may change in extreme cold or damp. Integrated circuits may begin to conduct when they shouldn’t, electrolytic capacitors may charge or discharge at different rates, and the specified values of resistors will change. All this can have components / transistors triggering when they shouldn’t and discharge the energy stored in capacitors etc. All bets are off unless the LED driver was designed to handle the climate it’s in.

-Thirdly, the truck itself expects a certain resistance value in the circuit to prove that the lamp is not burned out. Most LEDs mimic this resistance value so you don’t get a burnt-out bulb indication. However, this mimic value might not be super accurate. Whatever the circuit is doing to sense for the presence of the lamp, may be tripped up in cold weather when all the resistance values change. Anything that was calibrated for normal conditions may not work as intended in the extremes.


I figure shit out like this, everyday, for my living, for the past 30 years. My honest advice:

1- I would guess all our trucks do the same thing in the same conditions, but we don’t see it due to incandescent tail lamps or warmer weather.

2- when troubleshooting electrical ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS suspect the last change you made as the primary source of the new problem. 97% of the time you fucked it up. Every other avenue is a total and complete waste of your time until you prove otherwise. Never EVER, never ever, NEVER “sign off” on a change you’ve made, as “not the issue” or irrelevant, or a “red herring” no matter how much you’ve convinced yourself otherwise. I have learned this the hard way over decades of troubleshooting. On the balance of probability, you caused this problem by fitting aftermarket lights. It’s likely not even a problem, but just a phenomena you can now witness.

I would put your incandescent “winter tail lamps” back on the truck and be done with it until spring.

I could also be totally wrong, but I’m right 97% of the time. Let me know if you find it’s something else and good luck!

 

If the parking brake was engaged while driving, the only thing that will happen is this:


Regarding the tune, I don't believe that to be the culprit as it only makes changes to the ECM.

I know you have already looked at the stop switch, but this time take some resistance measurements. I have attached the documentation to this post.

 

No offense but you are grasping at straws here. You aren't doing any true diagnosing of the issue unless you pull a multimeter out and start measuring.


Just an example, I upgraded my motorhome to LED and switched it to a separate LED turn signal as well. Even installed a third brake lamp, also LED. After the install, with the engine running, the brake lamps would turn on and not shut off. This didn't happen with the incandescent lights. Why now? Turned out that in the turn signal switch there is a brake cancel switch override that puts 12volts out but milliamps of current. This tiny current was enough to turn on the LED lamps but the incandescent scrubbed it off without illuminating them. In order to prevent this I had to rewire directly off the stop switch. It took a multimeter and diagnostic to figure this out. Not a trip to the dealer or an ECM flash. @Stocklocker has some great suggestions in his post too, but to find them, you need to put in some work. Not adjust the air pressure in the tires next.

 

Like the last para of post 36?

Its an IT thing too.

 

Sometimes you can lead a horse to water, but they just won't drink; no matter how thirsty they are. Sometimes you got to let them desiccate.

 

Without a wiring schematic, dismissing the meso harness is just as flawed as pointing to it. That said, I doubt anyone thinks the meso harness is a poor design or low quality, but that doesn't mean there isn't a problem with it or someone building it made a mistake. I would assume they are hand built for the entirety of the process, but don't know that for sure.

The hand brake theory is puzzling to me, and others here. I would not put too much confidence in that without more explanation of how it contributes to causing this problem.

Until you do some actual troubleshooting, pulling a relay and playing with temps is just as effective as swapping other parts, so why not swap back the parts that changed right before you noticed this issue?

 

Well a potential victory for everyone saying it is the LEDs. Dealership in Anchorage said they see this all the time on LED (including stock LED) lights to include newly delivered trucks. They said it has to do with "the LED base" and condensation in the housing. They said resealing the housing should fix it.

So, looks like I may have been over confident in my understanding of the wiring diagram. Still not sure why the stock (incandescent) 3rd brake light is doing it as well.

I'll still test the parking brake and returning to stock. If returning to stock fixes it, I'll try sealing the housings.

Like I said, the weather will be too warm to duplicate the conditions for a bit, so I will not be able to give a definitive answer for a bit. Once I have that answer I'll come back and either say I'm a dumbass, or talk smack.

Edit: My guess is it will be the former.

 

Still has not gotten cold enough to reproduce the flashing. It is predicted to be cold enough on Monday, so perhaps I will have an update then.