STX4Runner
New member
You'll know it's working by the beeping noises it makes when a tire slips and that wheel is gripped by the brakes. I would think this would be an easy situation to get in to in ice and snow.
Bad weather - 4wd operation
- Thread starter derekp
- Start date
derekp
New member
Thanks. Sounds like it does the same thing as it does in 2wd the the rear wheels break loose. Mine never did this, even while moving up a pretty good hill and all 4 wheels started spinning. I'm starting to wonder if something is wrong with my rig.
derekp
New member
The computer intervenes quite often while in 2wd but never in 4wd.
jwkilgore
New member
I can confirm that the A-TRAC indicator does NOT light up on startup.
Edit:OK, apparently I can't edit or post pictures tonight.
When you shift from 2WD to 4-High, a green four-tires graphic turns on in the right gauge cluster to indicate 4WD.
When you go to 4-Lo, the 4WD indicator stays on and is joined by a yellow word "4LO", a yellow traction control "OFF" graphic, and the yellow words "TRAC OFF". "TRAC OFF" is directly under the 4WD indicator but is some distance down.
When you hit the A-TRAC button, the yellow words "TRAC OFF" go out and immediately above them the green word "A-TRAC" turns on. All other lights stay the same.
Edit:OK, apparently I can't edit or post pictures tonight.
When you shift from 2WD to 4-High, a green four-tires graphic turns on in the right gauge cluster to indicate 4WD.
When you go to 4-Lo, the 4WD indicator stays on and is joined by a yellow word "4LO", a yellow traction control "OFF" graphic, and the yellow words "TRAC OFF". "TRAC OFF" is directly under the 4WD indicator but is some distance down.
When you hit the A-TRAC button, the yellow words "TRAC OFF" go out and immediately above them the green word "A-TRAC" turns on. All other lights stay the same.
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Ducmonsta
New member
I can confirm that the A-TRAC indicator does NOT light up on startup.
Here is my dash in 4Lo:
https://drive.google.com/open?id=0B6n3ksFFWS-dRk4wd1ZiNU5OemRrSXp4SE1fcTMtQnJaSDc0
And after activating A-TRAC:
You're right. I just had to confirm myself. Learned something new today.
derekp
New member
The VSC works in 2wd but I've never seen it in action while in 4wd.
Jhalko
New member
Trust me, he's nudging you so the thread doesn't blow up into a bunch of arguing. Suggesting someone stfu because you don't like their post just incites an escalation, it is an Internet forum after all. He's helping you get the info you seek.
derekp
New member
This evening, I was driving down a gravel road and tried a few things:
2wd - hard acceleration, the VSC activated when the rear wheels began to spin
H4 - hard acceleration, all wheels spun until I let off throttle. No VSC activation
L4, pushed A-TRAC button (no indicator on instrument cluster, did show 4-lo indicator with audible beep) - hard acceleration, all wheels spun until I let off throttle. No VSC activation
2wd - hard acceleration, the VSC activated when the rear wheels began to spin
H4 - hard acceleration, all wheels spun until I let off throttle. No VSC activation
L4, pushed A-TRAC button (no indicator on instrument cluster, did show 4-lo indicator with audible beep) - hard acceleration, all wheels spun until I let off throttle. No VSC activation
1engineer
Moderator
Correct as usual...
I just came in off of snow covered roads. VSC works in 4HI and lights up the dash. Usually sensor problems light up dash lights when not activated so that leaves electrical problem. Fuse? Bueller? [MENTION=83083]rigtec[/MENTION]?
derekp
New member
I didn't check fuses, I figured if VSC worked in 2wd then it would work in 4wd--shared circuit idea.
whodat
New member
I kinda have the same thing as the OP.
Regular 2wd lights light up with the slightest wheel slippage.
4hi no lights light up when it would normally light up during 2wd.
But when trying to do some doughnuts in the snow with 4wd and lights start flashing and VSC kicks in.
My take away from it (keep in mind I'm no freaking expert):
2wd is overly sensitive to keep you from slipping and sliding all over the place.
4hi keeps me moving in what the truck thinks is a "tough" situation so slippage is expected and that's why it's not as sensitive.
That's how I feel when I transition from 2wd to 4hi and drive accordingly.
Regular 2wd lights light up with the slightest wheel slippage.
4hi no lights light up when it would normally light up during 2wd.
But when trying to do some doughnuts in the snow with 4wd and lights start flashing and VSC kicks in.
My take away from it (keep in mind I'm no freaking expert):
2wd is overly sensitive to keep you from slipping and sliding all over the place.
4hi keeps me moving in what the truck thinks is a "tough" situation so slippage is expected and that's why it's not as sensitive.
That's how I feel when I transition from 2wd to 4hi and drive accordingly.
rigtec
New member
Hi 1engineer/team,
I've read the last couple pgs of this thread, and have started looking into the 'Instrument Cluster' electrical system plot. Because this system is made up of part electrical/mechanical/electronics/canBUS, I'll suggest that we approach this from a purely 'methodical' POV. What I mean by that is... you could go nuts attempting to attack this problem with a 'component by component' approach; far too many players in this system to win it that way. Since this system is 'in part' controlled by our canBUS system, the first thing that I would do is to give the 'Main body ECU compu netwk' and 'canBUS' the opportunity to 'RESET' by disconnecting the truck's battery for no less than four hours or over night.
I've checked to see what fuses are involved in this (there are 3 different ecu fuses), but none control ONLY A-TRAC or VSC; ...I think the OP would be experiencing much more than just indicator lamp troubles if an ecu fuse were blown, so I'm leaning towards a needed ecu reset! 'A-TRAC and VSC' are both managed by the MB-ECU through the Instrument Cluster system. I have the electrical prints for the IC; which I'll post shortly but I need to convert them (on 'photobucket') from Documents on my computer, to Photos before I can do that... it's the only way I can share them (electronically) without "Mitchell" preventing the transaction! To make things easier for those who may not be too familiar with interpreting schematic wiring plots, I'll try and highlight anything I see that might be akin to this 4Runner's problem!
Cheers
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rigtec
New member
Since my last post I've been studying these two (scheme) pages in order to identify the most likely candidates to play a part in this 'Traction system fail' issue. Believe it or not, there aren't many components here that are 'Stand-alone' ...meaning that most of the circuitry that's on the print is 'Integrated' into a network of 'players/components' and are driven by the ECU's firmware.
There is a slim chance, however, that it could be one of the sensors that aren't communicating with it's assigned ecu, but because the OP reports that he does see an acknowledgement of A-Trac/VSC operation (on the IC) when in 2WD, I'm inclined to lean towards the possibility of a firmware "Hiccup" (glitch).
If you take a look at the two diagrams below, you'll see that I've marked certain traction related components with red and blue arrows; the MB-ECU in red, the Instrument cluster in blue and the 'Data' (canBUS) lines with a Green Circle. So the RED arrow is there to help identify the MB-ECU: "see below"...
Now the blue arrow (Top towards rightside) shows the ecm's power source/fuse labeled ECU-B fuse 10A. If you follow the arrows facing downward, they'll take you over to the next component where the IC is laid out, showing the 12V electrical stage crossing over to the canBUS (5V) side.
At the bottom left you'll observe the VSC-OFF IND, SLIP IND, and A-TRAC IND! What we do know is that there's nothing wrong with the 'VSC IND' or 'A-TRAC IND' bulbs because it has come on, but only in 2WD.
NOTE: If the OP tries a 'Re-boot' and it doesn't resolve this issue, I'll start looking for some 'feedback' sensors/switches that may be at fault and need to be checked, Rgds!
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BLACK-FL4RUNNER
Member
Mine doesn't have any audible beep when going into 4lo correctly. The light comes on and stays lit. (doesn't flash)
Here's a pic of my dash with 4lo, and then with 4lo + atrac.
