2 cheap and easy A-TRAC hacks - Toyota FJ Cruiser Forum
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post #1 of 312 (permalink) Old 03-30-2006, 03:24 PM Thread Starter
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Lightbulb 2 cheap and easy A-TRAC hacks

*DISCLAIMER* I don't have an FJ Cruiser yet and haven't tried these hacks myself. I need volunteers to try them and report how they work.


1- Using A-TRAC with rear locker engaged:

According to the wiring diagram for the 2007 FJC it looks like A-TRAC can be used with the rear locker engaged by disconnecting the signal wire betwen the Transfer Indicator Switch on the rear differential and the Skid Control ECU. There is a possiblility that it could set a code C1248 (open circuit in rear differential lock) in the VSC system but the DTC detecting condition seems unlikely in normal 4-wheeling situations: "At vehicle speed of 31mph or more, 3 seconds elapse after rear differential changes from free to lock".

The easiest place to disconnect this circuit looks to be at connector LA2, pin 11 in the left kick panel. It will be a light blue/yellow wire in a white, 11-pin connector. If this hack works like I hope it will, the ABS and VSC OFF warning lights won't illuminate when the rear diff lock and the A-TRAC switches are both turned on and the slip indicator light will only blink when the A-TRAC system is controlling wheelspin.


2- Adding A-TRAC to your FJ Cruiser:

It is as simple as buying the $60 A-TRAC switch from your friendly Toyota dealer and installing to the existing connector behind the switch panel. All of the hardware is already there, it is the same stuff used with the regular TRAC that comes on every FJ Cruiser. I am sure it will work on the ones with the rear locker but not certain about the base models without the locker as the TRAC ECU has different part numbers shown with locker and without; A-TRAC is not offered as a factory option without the rear locker. If you are not sure about spending the money you can also install a single pole momentary switch to the pink/green and black/white wires at pins 3 & 4 of the Active Trac control switch connector, a flat 4-pin connector that should be taped to the harness behind the switch panel.

Who will be first?

5/19/2006 update

An update with corrected information on the A-TRAC+rear locker hack.

I incorrectly assumed the Skid Control ECU supplied the signal voltage to the diff lock position switch, and then to ground. The signal voltage actually comes through the rear diff lock indicator LED in the combination meter, reaching ground at the diff lock position switch. The Skid Control ECU simply reads the 12v or 0v signal. No reference voltage is supplied by the Skid ECU to the light blue/yellow wire.

There are several ways of making this work, the key is to disconnect the Skid Control ECU from the rear diff indicator LED/switch circuit and supply battery voltage to the Skid Control ECU at connector A5, pin 1 when the ignition is on.

A possible way of making this work is to disconnect the light blue/yellow wire at connector LA2 and put a jumper wire at the Skid Control ECU (master cylinder and pump) between connector A4, pin 26 (light blue/yellow wire) and Connector A5, pin 1 (black/orange wire) to supply the 12v signal with the key on.


07-13-2006 update:

You cannot add A-TRAC to an FJ Cruiser that did not come from the factory with the locking rear differential. See posts by PRCruiser and gunther here:

http://www.fjcruiserforums.com/forum...854#post114854


INSTALL THE ATRAC SWITCH
USING ATRAC AND LOCKER AT THE SAME TIME

Last edited by MissFJ; 09-01-2006 at 05:19 PM.
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post #2 of 312 (permalink) Old 03-30-2006, 03:26 PM
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Re: 2 cheap and easy A-TRAC hacks

Quote:
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Who will be first?
probably not many for awhile because most of us will have some sort of UP package...
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post #3 of 312 (permalink) Old 03-30-2006, 03:31 PM
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Re: 2 cheap and easy A-TRAC hacks

How about you buy me the switch, send it to me, and I will see if it works.



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post #4 of 312 (permalink) Old 03-30-2006, 07:45 PM
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Re: 2 cheap and easy A-TRAC hacks

Mudd thief..............

Just smile and wave boys...just smile and wave....
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post #5 of 312 (permalink) Old 03-30-2006, 08:23 PM
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Re: 2 cheap and easy A-TRAC hacks

You sure sound like you know what you're talking about. Way over my head.
I think you could talk me into buying an FJ at over MSRP. Good luck boyz, let us know how it goes.
(let's see...was it the green wire or the blue wire I'm suppose to cut. I guess I'll go with blue since it's my favorite color)
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post #6 of 312 (permalink) Old 03-30-2006, 09:58 PM
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Re: 2 cheap and easy A-TRAC hacks

Whats the chances of doing serious damage experimenting with this?
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post #7 of 312 (permalink) Old 03-30-2006, 10:15 PM
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Exclamation Re: 2 cheap and easy A-TRAC hacks

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Whats the chances of doing serious damage experimenting with this?
As I sit here and wonder why the heck anyone would even want to hack it.

The upgrade package is the way to go. The price of the package is probably about what the replacement ABS/TRAC actuator is (without labor) after you farg it up!!!!!

If you want A-TRAC get it installed at the freakin factory. This is certainly the way to go! You get some more goodies with it and the vehicle is still a bargain.

The FJ has onboard it what amounts to a flight (event) data recorder. It records the "events" as you drive. Well, guess what records this info??? ......The abovementioned ABS/TRAC actuator of course, and the electronics attached to it.

Monkey with it all you want, the ABS/TRAC system is very similar to the one on the Range Rover Classic manufactured by WABCO (manufacturer of brake systems for commercial airplanes, very high pressure reservoir included) it, at the time was hailed as the only ABS system fully compatible with offroading. These things are very expensive to replace.

The FJ system has all the capabilities of the offroadable system above and it also monitors and records a huge number of operating parameters as you drive it (in case you crash, the manufacturer can defend itself in the subsequesnt lawsuits) notice I said "it RECORDS it"!

I have to admit, this is intriguing; but with things like throttle position, steerin' wheel position, speed, and whether, when and how long the brakes were applied being data-logged you are gonna feel really alone when you go to the dealer and confess after it's screwed-up!

Now that's a significant amount of processing if you ask me, and it's doing it while you drive it.....kinda watchin you and what you do. I'm nearly certain, like the Prius and it's imbedded RS3200 easter egg it will take at least another Re-programming to work properly.

In other words; If you mess it up, you've bought it gentlemen.

This "event" data recorder would be quite useful in denying a warranty claim because, not only will it mark when you did it, it will note the conditions it was operated under after it was done and for how long.

I can't wait to see how this turns out!

Love Ya, Mean it!

Last edited by RoverGGM; 03-31-2006 at 01:15 AM.
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post #8 of 312 (permalink) Old 03-30-2006, 10:36 PM
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Re: 2 cheap and easy A-TRAC hacks

Personally I'm not one to monkey around with it, but I do admit whether it can be done intrigues me.
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post #9 of 312 (permalink) Old 03-31-2006, 12:34 AM
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Re: 2 cheap and easy A-TRAC hacks

Quote:
Perv3rse previously said:
Whats the chances of doing serious damage experimenting with this?
That's my sentiments exactly. The blue or the green wire. Or did I say the green or the white one...damn I confuse....BOOM!!!
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post #10 of 312 (permalink) Old 03-31-2006, 12:42 AM
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Re: 2 cheap and easy A-TRAC hacks

Btw Alex, since you have only posted once, who are you and how did you come by these theories?
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