I can't have A-TRAC without a Rear Locker???

jong34 · 10-05-2006, 12:15 PM

Here's the story:

I have a FJC 4X4 Auto with the Convenience Pkg only, which means that I don't have a Rear Locker or an Active Traction Control System. I found out that I can buy the Active Traction Control Switch from TRDSource.com and its basic "plug & play", I install the switch and I have the A-TRAC System. But I was told that I can't install it without the Rear Locker.

Why is that? Don't they both do the exact opposite things. The Rear Locker justs locks up thr rear so that both wheels spin at the same speed. The A-TRAC system just gives me the ability to turn my Traction Control System on or off.

Is it an ECU thing? (System won't recognize the switch unless I have a Rear Locker Switch?)

This might be a noob question but HELP PLEASE!

BMThiker · 10-05-2006, 12:20 PM

Yeah, my understanding is that unless you get the rear locker, the wiring and programming for ATrac will not be there. Sorry dude. You should have joined the forum (or at least lurked) before you bought.

philipl · 10-05-2006, 12:27 PM

Kansas law dog did a nice write up on this. To install the rear locker is $thousands. And no you can't install the ATrac without it.

bigbill25 · 10-05-2006, 12:28 PM

Yup, you need the locker...

See:

http://www.fjcruiserforums.com/forum...rac-hacks.html

A-Trac switch install with pics

--Bill

Kansas Law Dog · 10-05-2006, 12:34 PM

I think you are on the right track with "is it an ECU thing." Without knowledge of how the ECU is programmed, there is no way to make the A-Trac work, unless you have the rear locker.

However, the rear locker is electronic, so theoretically a fake signal to the ECU (indicating the rear locker is off - not engaged) should be all that is needed, but no one has figured this out. I think only one ECU is involved, but one would have to review the electrical diagrams to verify. Electrical diagrams can be found here - Toyota FJ Cruiser: Resources & Documentation Archive

Unfortunately, you are one of less than half dozen people that have an automatic transmission with CQ, but no DL (rear differential lock). So not many people will be working on this. PRCruiser (a forum member in Puerto Rico) has asked the same question. You might want to PM him to see if there are any new developments.

jong34 · 10-05-2006, 12:43 PM

Thanks Everyone for the quick responses.

I initially didn't want the A-TRAC Switch, but when I saw it on TRDSource for only $50 I said "Why the hell not!"

I just couldn't get my head around why one system needed another system that does something totally different. But now I know its an ECU thing. Damn computers!

Thank God I asked questions before I dropped the $50, I could use it for GAS

Thanks for the looking out

lllateralus · 10-05-2006, 03:11 PM

Sorry man.. that must be a seriously dissapointing thing to read.
(that it CANT be done)

Oh well, its still a capable 4X4.

**trdsource** · 10-05-2006, 03:22 PM

Quote:

Kansas Law Dog previously said:

I think you are on the right track with "is it an ECU thing." Without knowledge of how the ECU is programmed, there is no way to make the A-Trac work, unless you have the rear locker.

However, the rear locker is electronic, so theoretically a fake signal to the ECU (indicating the rear locker is off - not engaged) should be all that is needed, but no one has figured this out. I think only one ECU is involved, but one would have to review the electrical diagrams to verify. Electrical diagrams can be found here - Toyota FJ Cruiser: Resources & Documentation Archive

Unfortunately, you are one of less than half dozen people that have an automatic transmission with CQ, but no DL (rear differential lock). So not many people will be working on this. PRCruiser (a forum member in Puerto Rico) has asked the same question. You might want to PM him to see if there are any new developments.

PRCruiser had asked for a quote on the rear locking diff and many other questions concerning the ECU but I think he has abandoned the idea for now.
Haven't head from him in a couple months.

Matt

**L8Apex** · 10-05-2006, 03:48 PM

If I remember right, the ECU in FJs with a rear locker is a different part number from the ECU in FJs without the locker. It probably has different firmware/software. That's why the "ATRAC button upgrade" only works on FJs with a rear locker.

This implies that you actually need the ECU from an FJ with a rear locker before you can get ATRAC to work, and faking some signal to the non-locker ECU won't work (and the locking rear diff probably won't work without the corresponding ECU either.)

But I bet if you installed the ECU by itself (the ECU for the FJ with rear locker), you could easily fake a signal to make it believe the rear locker hardware is present, and ATRAC could be enabled with the magic button.

Kansas Law Dog · 10-05-2006, 04:14 PM

Quote:

L8Apex previously said:

If I remember right, the ECU in FJs with a rear locker is a different part number from the ECU in FJs without the locker. It probably has different firmware/software. That's why the "ATRAC button upgrade" only works on FJs with a rear locker.

This implies that you actually need the ECU from an FJ with a rear locker before you can get ATRAC to work, and faking some signal to the non-locker ECU won't work (and the locking rear diff probably won't work without the corresponding ECU either.)

But I bet if you installed the ECU by itself (the ECU for the FJ with rear locker), you could easily fake a signal to make it believe the rear locker hardware is present, and ATRAC could be enabled with the magic button.

I concur with you assessment. Futhermore, upon looking further into the Electrical Manual, the 4WD Control ECU specifies (Rear Diff. Lock), which says to me that there may be a different 4WD Control ECU for vehicles built without the rear locker. If anyone wants to pursue this further I suggest looking at manual pages 321-324 of the Electrical Manual. I'm going to surrender, as it is above my understanding. Good luck.