Brake lights constantly on?

[rwh963]

I HATE DEALERS! i was just looking at the module and noticed DAMAGE on the housing. the top near the harness has heavy scratch marks, and the housing face now has a weird track imprint and a significant pushed in crack!

now i have to file a dispute with the credit card used, and send a complaint to the dealer. as mentioned, it isn't 100% confirmed if the module is the true issue (even the service writer said maybe once a year problem). now i have a damaged module. then tech poked and prodded for two hours, so who knows what else occurred. i did notice the OBD flap cover was dangling. this is sloppy work. see pics, tell me what you think(and save the "told you so" comments!):

the major crack is in the bottom left corner, the track marks near the center.

 

[rwh963]

crack close up:

 

[rwh963]

scratches/gouges on the top of module near harness:

 

[Jakeepoo3]

Oh shitty!

 

[Jakeepoo3]

C1246 master cylinder pressure sensor
This diagnostic should have been done with this code. This will prove if your abs actuator module is communicating with the stop lamp switch or not. By observing the voltage at the master cylinder pressure sensor which is inside the abs actuator module as you vary the pressure on the brake pedal. The voltage should increase as you depress the pedal according to the chart. If you're reading the stop switch voltages there then the abs actuator module is communicating properly.. he pulls the stop wire and the lights work.. did all your traction control and stability functions come back too with that wire out? Does your pedal ever get hard or spongy..

All the weasel had to do is hook his techstream to the DLC and push the brake pedal on his dumb lazy ass. These guys are mechanics (no offense) they just follow the flow chart. They're not electrical engineers. Then he bashed the computer nice. Like I said the skid control module/abs actuator is responsible for a lot of functions you don't even know are there. Cruise control is one. Is the VSC disabled dash light always on? The orange box with a truck spinning out? I would think your brake pedal would be acting weird too with a faulty computer. It regulates hydraulic pressure to your brakes independently. I almost ate sh!t when my abs module was acting crazy like yours on a hard braking sharp turn so be careful until you fix it.

 

[Jakeepoo3]

Yeah go out there and slam the brakes on some gravel. And spin out too. See if your a trac, downhill assist, crawl control or whatever you have work.

 

[rwh963]

Oh shitty!

i don't even know how or why this happened. did they remove the module? looks like a device was used to pry using the cover as a base.

 

[rwh963]

Is the VSC disabled dash light always on? The orange box with a truck spinning out? I would think your brake pedal would be acting weird too with a faulty computer. It regulates hydraulic pressure to your brakes independently. I almost ate sh!t when my abs module was acting crazy like yours on a hard braking sharp turn so be careful until you fix it.

yes, orange lights remain on. the dash lights come on when starting, go off, then reappear, and stay on. haven't noticed any pedal issues.

your module was going crazy? what was the issue?

 

[Jakeepoo3]

Is the VSC disabled dash light always on? The orange box with a truck spinning out? I would think your brake pedal would be acting weird too with a faulty computer. It regulates hydraulic pressure to your brakes independently. I almost ate sh!t when my abs module was acting crazy like yours on a hard braking sharp turn so be careful until you fix it.

yes, orange lights remain on. the dash lights come on when starting, go off, then reappear, and stay on. haven't noticed any pedal issues.

your module was going crazy? what was the issue?

All my abs functions were disabled too. It was just a dirty tone ring and speed sensor that calculates wheel speed which is another input to the skid control/abs module. That's what makes me think it's not a problem with the computer because your brakes are working fine and the skid control ECU is just shut down because of a faulty input. The stop lamp circuit... It says he tested it so I can't say he's wrong but I would want to know the results of that other diagnostic.

 

[rwh963]

Summary update:

1) $288 lighter, and don't know if i'm closer to an answer or not. if it is something other than the abs control module, then i'm going to have to demand a refund.

2) someone working on the vehicle damaged the module housing. i've taped over it to help protect it from the atmosphere. whether the module is bad or not, that should not have occurred. gonna have to submit a claim to the dealer. hopefully the tech will admit to it, that would make it easier. not sure if my auto insurer has a role to play here.

3) took 4runner out for a highway drive. TPMS light is off now, first time in ages. not sure if the system was reset, or they topped up all the tires during the rotation.

4) on the highway, tested cruise twice. never been used since 2007. worked flawlessly both times.

5) braking: haven't noticed any hydraulic issue or other issue. no brake light/abs light on the dash.

6) vsc/trac lights remain on, as do brake lights

7) speed sensors: where are they located, how many, best way to determine health?

8) can't really test abs action right now, and don't have any offload area to spin out hard. i know in the pastor i've had a couple of hard emergency brakes, recall the abs chatter kick in. don't recall if abs light comes on if abs is engaged.

 

[rwh963]

these are the abs speed sensors you are talking about? if so, really $30/4? cheaper and faster just to replace them all?

4 ABS Wheel Speed Sensor Front & Rear Right & Left Fits Toyota 4Runner Tacoma US | eBay

 

[rwh963]

took another test drive (at $4.25/gal!). exercised the 4wd system (4lo, 4hi, center lock). did nothing for the dash lights. at a stop, in park, i pumped the brake pedal. ABS light came on, then went off. fundamental issue still there.

 

[AuSeeker]

these are the abs speed sensors you are talking about? if so, really $30/4? cheaper and aster just to replace them all?

4 ABS Wheel Speed Sensor Front & Rear Right & Left Fits Toyota 4Runner Tacoma US | eBay

Those are the ABS wheel speed sensors for a 4runner and other Toyotas....but OEM sensors are anywhere from $100 to $200 EACH depending which dealer you get them from, the ones in your link are most likely made in China but may work OK at least for a while, but I guess it's worth a try since it's not a lot of money but save your old ones especially if they're OEM because they would be of a much higher quality.

Even if you bought them from Rockauto they are anywhere from $21 to $155 each depending on brand and quality but none are OEM.

2004 TOYOTA 4RUNNER 4.7L V8 ABS Wheel Speed Sensor | RockAuto

 

[rwh963]

Those are the ABS wheel speed sensors for a 4runner and other Toyotas....but OEM sensors are anywhere from $100 to $200 EACH depending which dealer you get them from, the ones in your link are most likely made in China but may work OK at least for a while, but I guess it's worth a try since it's not a lot of money but save your old ones especially if they're OEM because they would be of a much higher quality.

Even if you bought them from Rockauto they are anywhere from $21 to $155 each depending on brand and quality but none are OEM.

2004 TOYOTA 4RUNNER 4.7L V8 ABS Wheel Speed Sensor | RockAuto

wow, you're right. went on my discount site: $187 each discounted. t
lets hope these are not the problem. abs light is not coming on, but is in the braking system.

 

[BlackWorksInc]

Are you sure that the crack wasn't there before? The scuffs/scratches I can't speak to, but you stated that you replaced it with a used unit earlier.

replaced it with a used unit[/COLOR] and has run well for 120k miles; i believe that unit had 70k on it from salvage, so it has 190k on it now ...

In my experience used/junkyard parts are not gingerly removed, packaged, or shipped; we've constantly had to send back engines, transmissions, components from our junkyard because they do not take any care in removing them from the vehicle or prepping them for transport and they're not a small company.

I'm just playing devil's advocate here, the electrical testing the technician would have done should not have resulted in that crack to the module, not to mention that crack is filled with grime and dirt. Where it's located in the engine bay, that crack should be very clean and "shiny" looking if it's fresh (due to the fiber reinforcement it will sparkle a little).

Now if you told me that the connector housing or the locking mechanism was broken I'd lean that on the technician (might not even be entirely his fault, those damn connectors are so crunchy and fragile after a decade that even your best efforts to clean/lube/and be gentle can still break them... just ask me how I know... out: ).

~


Anyways, time to really dig into the entirety of the Stop Lamp Circuit and see if we can figure a better idea of what's going on now that we have some more information here. I will warn you guys, this is going to get technical, boring, and a bit wordy; but I think we're at the point of getting granular now, so no apologies on my end.

First and foremost, Have you been having ABS/VSC/TRAC/BRAKE warning lights turning on this entire time along with your brake lights? I was under the assumption that only your brake lights were staying on by themselves and not that you also had ABS/VSC/TRAC/BRAKE warning lights on at the combination meter.


Reading over the technician's notes and reviewing the wiring diagram I posted earlier, their diagnostic process seems sound and their suspicion that the Skid Control ECU has failed internally sounds valid. Though there is two parts of their notes that seems a bit weird to me (granted, these repair order notes are often supposed to be as short as possible, so details get lost in translation), the technician states that they found the Skid Control ECU "back-feeding" voltage from the STPO wire causing the brake lights to remain on. I am wondering if that was a typo and they meant STP or STP2?

The reason I say that is because if you look at the wiring diagram the Stop Lamp Control Relay's control circuit (the magnetic coil side of the relay) is provided power via the Ignition Switch and is then grounded by the Skid Control ECU via the STPO pin thus turning the relay on. Voltage output on this pin shouldn't cause your concern, but back-fed battery voltage on the STP or STP2 pins/wires would cause your concern (STP & STP2 are signal inputs that the Skid Control ECU and other ECUs use to determine if and when the Stop Lamp Switch is closed and to activate the Stop Lamp Control Relay via the STPO pin and thus turn the brake lights on). The technician does state that they inspected the wiring and found no short to ground which implies that the circuit for the control side of the relay has no path to ground except for the STPO pin.

The second thing that seems a bit weird to me due to lack of proper context/detail is the technician states "Removed STPO wire from ABS Actuator and then checked brake switch operation, OK". I am not entirely sure what they mean by "Removed STPO wire," it could mean they had the ABS Connector removed or possibly they de-pinned the wire from the connector (which seems more useful, so we'll go with that?) De-pinning the STPO wire would disable the ability of the Skid Control ECU from turning the Stop Lamp Control Relay on itself, so I wouldn't expect that de-pinning the STPO wire would affect the brake switch side of things besides set a DTC. I would be more curious what de-pinning STP and STP2 does and measuring voltage on those circuits without activating the brake switch as they should have 0 volts on them until the switch is activated. Unfortunately as I mentioned above, these repair order notes tend to get really simplified, vague, and sometimes weirdly translated (i.e. a service writer might take what the technician said and "dumb it down" for the customer) and so I wouldn't use this as anything more than a rough idea of what was done.

Something to note here is that the Stop Lamp Control Relay is not needed for the function of the brake lights nor for the direct function of the ABS/VSC/TRAC systems (though removing it will set a C1380 DTC). What the relay does is provide brake switch information (STP On/Off & STP2 On/Off Inputs) to various ECUs for the purposes of adjusting electrical load & signaling to an optional 3rd party Towing Brake Controller that the brake pedal has been pressed so that it can command the Towing Converter Relay to close and provide additional current on the brake light switch that would over-load the factory Stop Lamp circuit (a bit of paraphrasing on my part, but for our diagnostic purposes this is what it does). I was scratching my head for a little bit when I was digging deeper into the function of this circuit as a whole because it didn't make sense to me why the relay existed in the first place. The relay was added to the Stop Lamp Circuit in 3rd Gen 4Runners from 2001-2002 when they got the newer hydraulic brake booster and was retained for all following models. Double checking a similar model Camry, Corolla, and Highlander I found that the two cars do not use a Stop Lamp Control Relay and retain a simple Brake Switch activated system, while the Highlander does use a relay. In the Highlander's case the wiring is a bit different because unlike the 4Runner and similar Toyota trucks, the Highlander does not have a "Plug & Play" option for 3rd party Towing Brake Controllers; instead there is an integrated trailer converter that is used.

~

Final thoughts:

-I think the technician might be right that the Skid Control ECU may be failing internally and either back feeding voltage when it's not supposed to via the STP and STP2 pins or it is commanding the Stop Lamp Control Relay on when it shouldn't be.

-STPO is a ground-operated ECU output, meaning that the Skid Control ECU grounds that pin to turn the relay on, de-pinning the wire from the ABS Connector should rule that out (which it seems the technician did during their diagnosis).

-I would de-pin both STP & STP2 from the ABS connector and with the vehicle turned on and the brake pedal not depressed check STP & STP2 pins out of the Skid Control ECU for voltage, there should be 0 volts from those pins as STP & STP2 are voltage inputs meaning that the Skid Control ECU is looking for voltage coming in from the circuit and it is not producing a signal itself; if there is voltage coming out of the Skid Control ECU on those pins under the mentioned conditions, then it's likely the Skid Control ECU has failed internally. Additionally there should be 0 volts on the STP & STP2 wires under the same vehicle on, brake pedal not depressed conditions; if there is voltage on these wires under those conditions, there is a short to power somewhere back-feeding voltage into the circuit and could be your issue.

-If there is a short to power on the circuit after the Stop Lamp Control Relay side of the circuit, then I would look at Junction Connector J4 next, many of the wires go through this junction connector and it would be worth testing this connector next. This is a connector that doesn't seem too easy to get to, it's located just above the main harness after it routes through the firewall; but it's location and it's frequent use in this circuit makes it a top suspect in my book at this point. It is located close enough to the firewall and just under the windshield that it's possible if water was leaking/had leaked into the vehicle along that area in the past it could have caused corrosion to short multiple portions of that junction connector together. Note- it will look like it has a "dummy" connector plugged into it, that "dummy" connector is the junction bus bar and has small metal plates in it to distribute power for the multiple circuits.

-Another possible culprit for a short to power could be the Towing Brake Controller connector (Connector T6), again possibly due to corrosion causing a short between the pins, this guy is easier to locate and is found behind the driver's left kick panel; it won't be connected to anything.

-If you don't find any short to power or leaking voltage at those areas and it's still present, there's some sort of damage or corrosion somewhere in the harness; tracing it down is going to be very tedious and time-consuming (or if someone else is diagnosing it, very expensive).

~

I went ahead attached some files for you:

-A simplified Stop Lamp Circuit that I pulled from the C1380 diagnostic steps section of the FSM. I find this easier to use for visualizing how power flows from the battery to the lights themselves than the Overall Wiring Diagram.

-An unmolested Overall Wiring Diagram of the entire Stop Lamp circuit (this one is more in depth and shows a bit more detail on one page than the EWD page I gave you earlier)

-An Annotated version of the Overall Wiring Diagram with my notes on the sections of the circuit, where I think some good starting diagnosis points would be based on where you're at now and some clarifications that should help you visualize what I was saying earlier in the post.

-A Connector Location page that I annotated showing the locations of the J4 Junction Connector and T6 Trailer Brake Controller Connector as well as their colors if you wanted to track them down yourself.

I hope this helps you find a resolution to such a weird issue! This was a bit of a time sink, I didn't realize I've been working on this post for 3 hours now! :rip: But this is basically everything I can think of based on the information you provided and the information I have available to me.

 

[rwh963]

professor, thx for the massive reply! really appreciate everyone devoting time to this issue.

1) the crack: i can only say i am 98% sure it was not there before, but i can't say 100%. the truck has been one family owned, and i've been under the hood a lot, even more so taking it over full time several years ago. i was there when the brake booster was replaced. i saw the replacement, the garage saw the replacement, nobody pointed out it was damaged. the tech recently did not make note of the damage as a possible reason for module flakiness (if he caused it, he might have ignored it or didn't know he did it). it would take a concerted effort to crack that plastic in that area. nobody else has ever worked on it after installation. the replacement part would have had to pass salvager inspection, our inspection, the installer garage inspection, never being noticed since 2013, and not noted by this most recent diagnosis. hard to believe. the marks look fresh to me.

2) electrical/electronic discussion: i'm new to reading and trying to absorb terminology and procedures and connecting dots, so talk to me like i'm 5 years old! i don't even know what STPO is!

as far as i know, this issue is at least 3/4 year or more old. i don't see my brake lights, of course, so i didn't know they were running.

let me clarify something you said "First and foremost, Have you been having ABS/VSC/TRAC/BRAKE warning lights turning on this entire time along with your brake lights? I was under the assumption that only your brake lights were staying on by themselves and not that you also had ABS/VSC/TRAC/BRAKE warning lights on at the combination meter.

the ABS light has never stayed on. the BRAKE light has never stayed on. the VSC OFF/SLIPPERY CAR/VSC TRAC lights AND brake lights are always on when the ignition is in the on/start position. they are not on in the ACC key position. when i start the vehicle, the VSC OFF/SLIPPERY CAR/VSC TRAC lights come on, disappear, then reappear within seconds. the brake lights are always on when the engine is running. the brake switch activated the brake lights normally with no key/ACC.

i don't recall if the ABS light comes and goes with the other dash lights upon start up. i can induce the ABS light by pumping the brake pedal.

 

[BlackWorksInc]

I don't know what STPO means, Toyota is not always very good about giving granular information to technicians (which honestly would be super helpful when you're running into weird issues). You just have to infer it from the circuit and such, but in this case I'm going to go out on a limb and say that "STPO" stands for "Stop Lamp Output" or something like that. STP, STP1, and STP2 are similarly probably "Stop Lamp Input, Stop Lamp Input 1, Stop Lamp Input 2." What's more important is recognizing where the wires go to (i.e. from the coil side of the relay the wire ends at the STPO terminal at the Skid Control ECU) and having a rough idea what that wire/pin does.

As I explained, given how the circuit is designed and how the Skid Control ECU works; I know that for all intents and purposes the STPO terminal is a ground that the ECU turns on when it wants to close the Stop Lamp Control Relay. It uses the Brake Switch and the two different inputs of STP and STP2 to determine when it should open that relay and to verify that the circuit is functioning correctly.

 

[rwh963]

when you say "skid control ecu", are you referring to the abs control module, or is the module sending info to the skid ecu?

 

[BlackWorksInc]

when you say "skid control ecu", are you referring to the abs control module, or is the module sending info to the skid ecu?

Skid Control ECU is what Toyota calls what most people refer to as the ABS Module, this is mainly because it's technically a module that controls ABS with EBD (Electronic Brake force Distribution), BA (Brake Assist), VSC, and TRAC System and so rather than calling it an ABS/EBD/BA/VSC/TRAC module they call it Skid Control ECU.

I was trying to use roughly the same names you see in the diagrams I posted so it'd be less confusion since there's a lot of terms and acronyms in there.

 

[rwh963]

Skid Control ECU is what Toyota calls what most people refer to as the ABS Module, this is mainly because it's technically a module that controls ABS with EBD (Electronic Brake force Distribution), BA (Brake Assist), VSC, and TRAC System and so rather than calling it an ABS/EBD/BA/VSC/TRAC module they call it Skid Control ECU.

I was trying to use roughly the same names you see in the diagrams I posted so it'd be less confusion since there's a lot of terms and acronyms in there.

thx for clearing that up. there are a lot of terms out there! the dealer called it in there print out an "ABS Control unit". the parts dept. ID'ed it as a "Master Solenoid". and you just used "Skid control ECU". no wonder people get confused!