ABS Light after LED install...

[eddie4christ]

Alright this is so stinkin' frustrating... I installed a LED 921 bulb replacement into my third brake light... Works and looks great with my LED tails, but the next morning I start the truck and put in drive and the ABS light pops on the dash... convenient. So I unplugged the LED and put the original back, no luck, still on... Unplugged the battery cables and then replugged them in, still nothing... Now my final option is going to the dealer but I know they are going to have a field day with that... Anybody else have this prob?!?

 

[bgmac]

I would say it just a coincidence that the light came on after you put that bulb in. So with that said ,have you brakes and system checked out. Im not sure if that will come up on a scanner or not. Take it to Auto Zone and find out, its free. Your abs sytem does a scan each time the vehicle is started, so something tripped it.

 

[shootmymime]

most of the time unpluging the batt. cable will not clear codes, i have found on 4runner you have to pull the EFI fuse under the hood, and WAIT 30 SEC!!!
1.
2.
3.
and so on....

keep waiting...


30. then plug it back in and start it, see if the code is cleared, if not then go to orielys and scan it..... but if it goes off... then comes back on with in a day or two then something is wrong....

in the mean time keep your LED buld pluged in, it should have no affect on the ABS sensor on your axel

 

[eddie4christ]

Yeah I went to Advanced Autoparts to get the scan done, and they said it would be no good to scan if there is no check engine light on... But I'll check that fuse and see if that works...

 

[Stick Figure]

doesn't the 98 still have the diagnostic port under the hood? not the OBDII port, but the old school toyota diagnostic port? If so you should be able to use a paper clip to jumper it into diagnostic mode and get the code that the ABS computer is seeing.

 

[Ron Helmuth]

resistance is different

Your ABS code is lit up as a way of telling you the brake light is "out"-it is not sensing the voltage equivalent to the former
bulb.

This is why some LEDs require a resistor in line with the wiring path.

Clear the code-plug back in a real bulb and see if I am full of crap....

See if this has affected your cruise control also-that is the effect it had on 2nd gen Runners when the stop light/tail light bulb was improperly replaced.

I looked into using an LED for the 3rd brake light awhile back and avoided it as no one could assure me that the problem you describe would not occur....

 

[borgzman]

Re: resistance is different

Your ABS code is lit up as a way of telling you the brake light is "out"-it is not sensing the voltage equivalent to the former
bulb.

This is why some LEDs require a resistor in line with the wiring path.

Agree
When the shop installed my after market spoiler, they were forced to plug back the bulb third brake light together with the LEDS that comes with the spoiler. They said they noticed strange lights in the cluster(I didn't know if it was ABS) LEDS draws less current and voltage for the system to detect. Now I have two third brake lights glowing when I press the brakes I should have meaasured the current and voltage drop accross that line there and computed an equivalent resistor in series and send back to tha system the correct load.

 

[benormous]

A similar issue was discussed here: http://www.toyota-4runner.org/showthread.php?s=&postid=347264#post347264

If I were installing LED tails, I would take out the stock bulb assembly and measure the resistance. Then measure the resistance of the LED assembly. Then add a resistor in series to make up the difference.

Thats my opinion. But if you look at the post above there are a couple different opinions.

 

[borgzman]

Actually I'm confused when it comes to those circuits in cars I refused to think (shocks! I'm too old for this!)..What comes back to my mind is that a resistor is added to oppose current? right? And a voltage drop is produced between its terminals? And circuits are complete without adding resistors?(Of course resistance can be obtained anywhere in the Ckt), and they are added to correct current and voltage drawn or being supplied?... So, is the car system really after of the resistance that is being sense from the brake lights, or the current and voltage is very low for it to detect that a bulb is there?
I have two third brake lights, one in the original (its bulb) and the LED assembly in the spoiler. I think there are 8-10 LEDs and a white rectangular(I'm not sure) which I presummed to be a 1-2W resistor already built in the LED assy, and if its 1 watt it is good as "short"...
So whats the known good solution to this?..Resistors in series?
I'm just waiting for these threads come up with one, as its also my problem ..and sorry for my english as I maybe confusing..LOL!

 

[benormous]

OK, voltage, current, and resistance are all related by Ohm's Law:

V = I * R

A current flows when there is a voltage across a reasonable resistance. With no voltage across a resistance, there is now current flow. Likewise, with no current through a resistor, there is no voltage drop. You are right, the computer is probably not measuring the resistance of the tail light, but rather the voltage. The computer might think it needs 12V to "overcome" the resistance of the stock tail lights. When you put in the LED's, the resistance might be much lower and the computer supplies less voltage to overcome this resistance. If this voltage is not what it expects, it throws an error. This may be an over simplification of the system, but it is probably a safe assumption as to how it works.

Since we cannot change the source voltage, the only thing we can do is to try and match this resistance. I'm not doing this mod, so I cant really do this myself and give a definitive answer on what seems to work.

I do know a little about DC circuits though, so I can try to help.

Also, resistors are measure in Ohm's, not Watts. If a resistor value is given in Watts, something else is assumed, possibly maximum current.

P = I * V --> P = I*I*R

In general, when using an LED in any DC circuit, you must use a resistor in series with the LED to limit the current or it will most likely burn. There is probably a resistor in the LED assembly to keep them from burning, but its hard to say if the manufacturer matched the resistance of the stock assembly.

 

[borgzman]

"The computer might think it needs 12V to "overcome" the resistance of the stock tail lights. When you put in the LED's, the resistance might be much lower and the computer supplies less voltage to overcome this resistance"

Yes..exactly...

Since we cannot change the source voltage, the only thing we can do is to try and match this resistance

Bingo! that's it..!

There is probably a resistor in the LED assembly to keep them from burning, but its hard to say if the manufacturer matched the resistance of the stock assembly

Correct.. those basics are coming back to me now..thanks

Also, resistors are measure in Ohm's, not Watts

What I mean is f its that "rectangular ceramic type" they are available in our country @ 1 plus watts So if you'll buy a 12K ohms@ 1/4 watt, they will give you the "color coded" ones and not the rectangular ceramic I'ved mentioned above..So by glancing at components in a PCB then that 1 plus watt resistor regardless of how many ohms resistance is one of the biggest noticeable component in an analog surface mounted ckt..and yes the unit in measuring resistance is ohms..

Thank you..for this discussions its actually interesting and helpful. I am actually working in this 14 years ago and had bad experience in employment, so I refuse to think even the ohms law being applicable and usefull in modding car electronics.. and when I see discussions like this its just in the tip of my mind still I'm rusty and I would like to help but my mind needs exercise

 

[eddie4christ]

took it to the dealer, he said that the error code is: 49, comes back to a brake pedal sensor error, AKA, the tird brake light is out! haha, so they said to take it back to stock lighting, tails and third brake! But I think I am going to pull that fuse and see if I can trick the computer, and if that doesnt work I'll get a resistor... This all happened within the past two days...

 

[borgzman]

took it to the dealer, he said that the error code is: 49, comes back to a brake pedal sensor error, AKA, the tird brake light is out! haha, so they said to take it back to stock lighting, tails and third brake! But I think I am going to pull that fuse and see if I can trick the computer, and if that doesnt work I'll get a resistor... This all happened within the past two days...

Ha!ha! x2, I know you're excited to have the LED third brake. Its brighter than stock,enough to catch attention to the driver behind you.

..At the instant you step on the brake, it commands a "Hi" input to the switch(Hi - coz its most likely a digital switch) which is MAYBE connected to the system control and sensors triggering the ABS switching to display)..if I'm correct. The switch throws a 12V of unknown current to the stock 3rd bulb( basing from previews replies) The only resistance there, is the resistance of the wire and the resistance of the filament of the bulb. Base on the other thread/link above, He measured it at 6 ohms (correct me if I'm wrong).. So the value of the resistor(in ohms) to be added in series, is the the difference when subtracting 6 ohms(stock bulb resis) and the actual resistance of the LED assy. In my LED its almost zero. IMO I would still buy 6ohms.

What confuses me is the other thread is suggesting it to be connected in parallel(base on the illust.)?? Not only it decreases the total R(same comment fr d other guy) its prone to over heat??..if I'm correct.

And those resistor online are expensive for trial and error purposes, IMO those "wirewound resistors" from Radioshack will serve the purpose..its just my opinion
http://www.radioshack.com/search/in...wound resistor&origkw=wirewound resistor&sr=1

and correction for myself LOL!, the ceramic type resistor I mentioned in my previews replies is the Wirewound resistor (old skol here)...good day to yo all!! I just realize that I spelt previous wrong!! :bash:

 

[dangerbird]

The same thing happened to me when I replaced the reverse lights with LEDs. Glad I saw this.

 

[DavidAlexander]

I have a pair of resistors for sale that work with the LED 3rd brake light/ Tail light mod.

You will only need to run one before a tail light. That will provide you with the proper resistance to trick it into thinking there is a filament bulb. Once you intsall one of these, disconnect your battery for half hour and then your computer will reset and the ABS light will be off for good.

WHILE YOUR ABS LIGHT IS ON YOU DO NOT HAVE ABS. Might want to solve this before winter.

$10 each including shipping.

 

[gmaneod]

I know its been awhile since anyone posted on this thread I am looking for a resistor for my third brake light any reccomnedations?

 

[DocW8494]

Just want ed everyone to know - THANKS!
ABS light has been on and thought something was really wrong with the ABS system which is okay, don't really like ABS anyways, but the dash idiot light is annoying!
Had my daughter check the brake lights with me last night, she didn't like helping me! But the third brake light is out and will replace later today or this wknd.
Amazing how the ABS light comes on for the third brake light but not the other brake lights. Plan on replacing with the LED light (resistor type too), will let everyone know how it turns out.
Thanks again!