I was a young mechanic working in NW Pennsylvania in 1986 when the "third brake light" was first required on all vehicles and being certified to do inspections I knew it as a collision avoidance light. Thank you for another video with invaluable information. You are the best!

I always wondered if the manufactures go back and revise their wiring diagrams after finding out how many good techs have been misled by this kind of stuff. Thanks so much for educating us Jake!

As Ivan would say this is so cool!

Had a customer come in with an 18 Toyota Tundra and it wouldn’t allow the gear selector to move. Turns out he installed a new tail light assembly but it did not come with bulbs. Putting a bulb in and replacing the blown fuse for stop lights fixed it. Fuse would blow every time brake pedal was applied without a bulb in it.

I had a similar experience with a Subaru, which locked itself in park when the rear right brake light fuse was blown. I had put an incorrect replacement bulb in for a blown bulb, and it blew the circuit fuse, and that prompted the car to lock itself in park for safety. The diagnosis was easy because I knew what I had done, but it was a lesson that these systems use that circuit for all kinds of decisions like abs, traction control, etc. As in your case, the code was a brake circuit code.

I believe the diagram is right in that it is a pull up circuit, the difference is that with the circuit open(bulb blown) you are seeing a bias voltage. The PCM sends out a bias voltage with very little current to check circuit integrity. When the circuit is complete that bias is pulled low. Also if you read in the trouble shooting data right above the circuit system/ testing steps, it states in circuit system/ verification "Inspect for proper operation of the stop lamps, including the CHMSL. Refer to Exterior Lighting Systems Description and Operation" Maybe they should of highlighted that or included it in the circuit system/ testing steps.

Corrosion on my third brake light socket on my 2008 Toyota Corolla disabled my head lamps and high beams. Once I cleaned the green corrosion and a little DeOx they all came back to life. Good job Sir!

I've heard the same problem exists in some late 80's or early 90's cars. The backup bulbs are the "pull" resistors for the circuit. Without the bulbs, the ECM thinks the engine is in gear all the time. When the engine is actually put in gear, the engine stalls as the ECM fails to compensate for the engine load.

i had one of those about a year ago never figured it out customer didn't want to pay for a full diag thanks so much very helpful information

I guess I've just gotten lucky. But I'll be making sure I check that from now on. You're awesome

I appreciate the screen share that eliminates glare and pointers edited in for visuals.

Id like some info on the test leads you have and some of the other equipment you use. Great Channel!

Such a cool thing, right? And you wouldn't believe how many times someone has told me they "have a short to power" on a normally low [if complete] sensed circuit... but, simply because they were testing *only* with a 30 Mohm impedance DVOM... on an *open/unloaded* circuit. And I don't normally use the same setup as you -- with the bulb -- but I always have my fine-tip 40 ohm [Snapon or OTC] testlight with me, and clamped to a good ground... and if I clip the red DVOM lead to the tip of the test light and re-probe the circuit right in front of them, shoosh, the code is gone and the stray circuit voltage drops to zero (as it should). You can actually see the gears start to turn in their head (and that's a good thing). 👍

I love your videos man. Always learn something, I knew what was up with this one straight away but didn't know the diagram was wrong on it. I always watch your videos and thought I was subscribed and wasn't I am now. Thanks for all the time you put into these to help us all figure these systems out, they are getting more complex everyday.

Wow, wow! Amazing! I loved the video. Three days ago, in 2011 Mitsubishi Lancer a customer complained about losing power doring costing and experiencing a lack of acceleration when they tried to turn on the lights. Upon investigation, I discovered that one of the brake lights was burnt out. I wasn't sure why this happened until I watched your video. Thank you once again!"

I find that the service manual info only gets you so far. You really have to think about it and read between the lines. If I followed it to the letter, I'd be putting PCMs in Toyotas all the time. Sometimes, the simple stuff can throw you for a bit. Interesting video.

That's some amazing work you do. Thank you for helping out everyone else for posting these findings. 👍😁

17:49 Jake you write letter to Alldata and they add to TSB?

Incredible info. Thanks Jake.

You can see the challenge in making an ECM and TCM high side switched third tail light full diagnostic circuit (circuit open, circuit shorted to +12VDC, etc.) when you have a center stop lamp to ground and you tie both the ECM and TCM inputs directly to the bulb. You have to assume that the bulb will always pull the circuit towards ground in order to design an analog diagnostic voltage divider (probably pulled to +12VDC through a diode) processed by an A/D channel. I do think that the ECM or the TCM input divider approach is correct, but not when you connect them together. However, we have to ask the question why doesn't the BCM monitor the CHMSL light? To close the loop on diagnostics the controlling module should monitor if the commanded load is turning on, especially if isolated by a relay. There is more strangeness to the circuit. First of all the relay should have a noise suppression device on the relay coil (either a resistor or a diode), and you would put the relay output fuse before the relay switch and not after it. You need to protect the wiring from B+ to the relay in case of a short to ground.

Good morning and keep up the great work!! Great video!

Keep these videos coming!!

Way cool tip 👊🏻. Keep these coming

Really enjoy your content and your very well put together videos. Cool hearing your back story with Sean this week. Quite the clever circuit, definitely more than a simple pull up or down resistor going on here so recognizing bias voltage vs voltage drop from unwanted resistance or an open circuit is critical. I still like to trace out my diagrams with color pencil when you get into series-parrallel circuits espically if chasis is providing the unstable high side of the circuit with this particular one being 12V switched on a safety critical circuit. A methodical approach with testing vs guessing like your demonstrate very well is so refreshing and educational to watch. You sure make a guy wanna buy a Pico! Thanks again.

Awesome job Jake! I kinda laughed at the end with you. Great diag and hugely informative for anyone who may experience this in the future. Thanks bud!

You learn something new everyday! 😁

AS SOON AS YOU WENT TO THE DIAGRAM MY HUNCH WAS A BRAKE BULB ISSUE.NICE JOB!!

Love your videos.. excellent knowledge

Wow that is crazy , a brake code for burnt bulbs . Another informative video thank you👍🏼👍🏼👍🏼👍🏼👍🏼

Wow. Gotta love them OE diagrams. I’ve seen that happening on a Silverado, luckily i threw a high mount bulb in it as well so i just assumed the brake light switch fixed it hahaha now i know what that code actually pertains to. It always stumped me because soon as i see a brake switch code, i immediately check the brake light operation and they work, crazy how 1 bulb being out can cause a circuit issue. Your badass brother

JAKE, AWESOME approach and diagnoses thanks for sharing.

Very informative video!! Thanks again for valuable info!!!!!

Well done 👍

I remember back in the days of Rear Wheel Anti Lock brake systems having a code 9 I think that was it. When you ran the ABS test code 9 came up. When the 3rd stop light bulb went out, there was the code. Great diag and fix!

Nice job for fixing the problem..

I expected it very early on :-) VW has the same "issue" with many Cars.....blown bulb and Brake Switch Errorcode. And Cruise Control does not work :-)

Great find..!

I hope one of you contacted Alldata and told them the diagram was wrong. Thanks for the videos. Been doing his for 40 years. Always learning.

Thank you!

❤ thanks for sharing nice work

Wow that blew my mind 😮

The ECM is looking for a pull up signal. The PID changes state when pulled up. The voltage(s) from the ECM and TCM are bias voltages to monitor circuit integrity. Not brake apply detect.

On my 2004 silverado, I lost my cruise control... Turned out being because I installed an LED bulb in the CHMSL... Put incandescent bulb back in, and cruise control fixed... Thanks for your work...

Wow …… thank you really good video

Great information

Nice video and great tip. I remember Eric O. from South Main Auto Repair had mentioned that before about checking the brake lights. Thanks for sharing.

Priceless

Thank you sir for sharing your knowledge

as soon as you said brake light switch code i thought need to see all brake light bulbs working because cars are getting too smart in a dull way thank you for the videos

I had to watch the video twice to pick up on what you were saying. At first I thought you were saying the relay grounded the circuit down to turn on the light. I had to watch a second time to realize that you were saying the "pull resistors" in the modules are pull up, not pull down. The relay still pulls up to activate the circuit, but that leaves only the bulbs to pull it down to the inactive state.

Very interesting, this indicates that if one or more bulbs were tied in on this third brake light circuit the DTC's must be very distracting😋 Thanks for sharing Bro😍

Thank you very much ❤❤❤

Thanks for this video. My daughter owns a 2010 Cobalt and she probably was close to having this code because a while back, two out of the three bulbs in her third brake light were blown.

you would think the bulbs being out in the third brake light would throw a bulb out message as the circuit is monitored for opens. I enjoyed the pod cast Jake👍👍Cheers

Top diagnose!

Alright Jake, pretty interesting!!!

Learning to read schematics, will help you diagnose what others cant. Thats what separates a mechanic from a technician.......

Wow, I've never run into that code yet, but now I'm prepared! Thanks for the Tip! Are you sure it's a pull-down circuit? Can't it be a pull-up and that is just bias voltage to check for circuit integrity?

that's nuts. seems that should not be the way? Thanks charlie ,wis.

That was cool, Jake! Now if this was a European car, it would tell you on the message center exactly which bulb was burnt out... Because Euro cars are superior to all other cars 😆

Jake, those brake lights always seem to mess me up, not to mention what happens when the diagram is wrong. Thanks for Sharing! 🙃🙂🙂

thanks excellent

Lmao 🤣 I love this excellent video. Tbh the voltage would throw me off but id would of check the bulb function 😂.

I had a similar experience with a Corolla: some sort of brake switch code and the issue was the right side brake bulb had a poor connection to the socket.

Its looks similar circuit fault when ground is missing on tail lamps it effects other marker and indicator lights.ecm is getting signal pull down through a bulb 💡 😂crazy is that..great great explanation 👍🏿 sir.

Thank you sir...

another reason to check all lights before diag.

that was a good one

Oh I neverrrrrrr would have figured that out and it’s still quite confusing to be honest. I have a Silverado here now with this same issue. Let me find a pedal depressor! 😖🤦🏽‍♂️

It's crazy when it's right in the data, but you'd never know what PID was the magic one. (or, sometimes even where to find the right menu)

Amazing circuitry imagination my friend, but I think that this design, or circuitry of the Brake Sw., needs to be redesigned. Perhaps with a diode a possible ground return could be solved, or perhaps a +B but this is only my assumption since the circuitry must be extensively analyzed until the problem is solved. VERY GOOD VIDEO. Greetings from Tijuana 🇲🇽 Mexico 👍👍👍

Talk about misleading information! Throw a code for a brake pedal switch when a bulb is bad! And with the schematic wrong, it's no wonder people go down that rabbit hole. Great case, Jake!

Really cool.. I have to look at a diagram to see why u only have 7v with bad bulbs.. nice video

I would really like to know how u made your test light tied into your dvom .Great job though 👍

Awesome 😅

Grasias

Does AlLDATA have a way to report a wiring diagram mistake (and either fix it on their redrawn diagrams, or add a note that the diagram is incorrect)?

So that means the ecm ,tcm and bcm need to see 0 volts through the light bulb filament to ground in order to see as "Released", otherwise it'll show 7.5 volts and therefore the P0573. Thanks for sharing.

SHARP Automotive Diagnostics & Programming 👍 From Nick Ayivor from London England UK 🇬🇧 ⏰️ 21:33pm

Very interesting so TCM or ECM actually loking ground through third brake bulb

ty great info. Outro should be your intro tho,.

The ecm and tcm are putting a bias voltage on the circuit that the bulb pulls down, when the bulb blows bias voltage goes up. Just think about it and you will realize the diagram is not wrong.

smart man for sour 👍👍👍👍👍

That blows my mind see what I did there 👍

Had a Toyota Avensis in Europe with this kind of problem. It was lightin up abs light. Weird design 😅

What confuses me: The ECM and TCM are both tied directly to that center light... So if they are applying a high voltage at all times for a pull down circuit-- then why isn't the light ON at all times? How is that ECM pull down circuit using the bulb as a ground without lighting it?

This is a lot like Nissan with their transmission code that sets when a brake light is out.

Very useful and enjoyable tip of info

I watch one of your videos and you put some kind of listening device by the back tire and we heard the noise the rear end was making can you tell me what that device was . Like to get one so i can use it to hear where the noise came from. Kept up the good videos. You are going to be one of the best mech on you tube thank you

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👍

What about whith my is has tha same code i already change the brake switch y still has de code but stop lights when the cars is on the light is on all the time and my car has check engine reduce

nice one Jake ,crack open a beer for yourself good job

good god thk for this video, wow very impressed with you working it out, so it need the resistance of good light bulbs in circuit, gm lead tech down rabbit hole isn't that nice.

It doesn't make sense to use a pull up on a circuit where you are looking for a high signal. Unless you are monitoring for blown bulbs, but you wouldn't rely on one module to pull high and one to pull low. Plus with the 9V with only the TCM on the circuit it seems more like it's floating and there is no resistor at all. Yeah, the bulbs pull it down and resolve the code, but seems there is still the issue of why is one pulling down and one floating or possibly be pulling up? Nice catch though!

I watched your video and none of the conditions applied to the code and I had an intermittent brake light and warning for brake system malfunction and service brake system well my shop foreman came in this morning when I'm off and asked where I left off told him I had battery voltage on the signal wire and good power and ground and the scanner was showing circuit and pedal picking up applied and not applied he said I put brake fluid in it and it's off your fired...

🤣🤣🤣 that was awesome

I need your help Can you tell me what is the code exactly U0010-88 On jeep renegade

Like Hyundai kia trans in limp from water in back up lamps 😅

😃