Traction control

Yeah his isn’t lifted crazy

 

Yes they do. But they aren't usually done by shade tree mechanics and they use parts that likely have been vetted by engineers to work correctly.
I've been modifying a Jeep since 1982. Some mods worked as advertised or even better. Some were total flops. You just learn to accept the failures and enjoy the success'. But I'm never surprised on which way it goes

 

I hear yuh I grew up around my dad lifting trucks and Jeeps. The shop that lifted mine actually does full on rock bouncer and v tub Jeeps and full size lifts. I wanted a 6112 front with a 5100 rear but when I got it they decided to use a top strut spacer on the 5100 and the stock Toyota spring. But because I don’t wheel and they said it was back order they did this route. Later on I may swap out the top strut spacer for an 887 spring or something. But the ride quality is nice other than this issue

 

OK - a Way off the wall stab in the dark so no flames please .... Since it's doing this when cornering are the wheel speed sensors thinking a wheel is spinning too fast/slow and the traction control is trying to correct ??? i.e. Wheel sensors ???

 

Tough to read the photos, but I'm looking for issues.

You mention body roll again. I still don't think that can have anything to do with it because as far as I know there is no tilt sensing correction in the VSC of the Tacoma. I will look through the FSM for it, but for now I don't think it's in the controls. If there is correction based on a tilt value there is an slight possibility this could be it. If body roll is part of it it will be from inducing body sway on turn-in which you'd see as a spike in measured yaw rate or from roll steer causing a variance in steering ratio from stock.

Looks like the measured yaw rates are in the ballpark and the sensor is functioning correctly, but obviously something is deviating outside the allowed window in this scenario just enough to fire the VSC system. I'll attach a very simple expected yaw rate plot to help give you an idea of where the values should be under different conditions. The steering ratio of the Tacoma I had to guess and it's going to vary vastly from center to lock, but it's a crude approximation to start until I can get more accurate info the Tacoma steering ratio. I assumed SBDC wheelbase.

If the left front brake is engaging during a tight right turn that means the VSC is correcting for oversteer. IE it senses that the yaw rate is larger than expected for the vehicle speed and steering angle.

It could be just enough in the combination of larger tires creating higher ground speeds than the vehicle expects (it's programmed to get speed assuming stock tires size), change in slip angles due to different tires, different alignment and body kinematics creating a slightly modified steering ratio, and mildly aggressive driving right to the limit that creates the deviation just outside the allowed window.

What I do see is the the "yaw rate sensor" and "yaw rate value" are not agreeing. I think the "yaw rate value" is the expected yaw rate (I need to verify this) so that means it's calculating an error in these situations of 5 deg/s which is over 10%. I think that should be nearly enough to fire the system. The values also indicate it senses an oversteer condition and this matches with the above note that you're experiencing corrective actions for oversteer .

You probably will need to compare to a truck under the same conditions to see the normal deviation. For some reason I think your mechanical setup is just over the line of the programmed control equation to cause the deviation and have VSC intervene. There may be ways to get it back inline though.

 

Wheels speeds look reasonable and this is a VSC issue, not traction control.

 

If i'm reading the above snap right it looks like only engine cut is active.

Also, is your truck a 2.7L 4 cyl manual? What size tires came stock?

Both steering angle value vs steering angle sensor and yaw rate value vs yaw rate sensor are not aligned. I'm trying to figure if these are calculated vs measured comparisons and therefore telling the skid control ECU it needs to intervene. My best guess right now is this is the issue for some reason.

Tilt and therefore roll angle is not in the VSC data list. There is a mention of the truck sensing bank angle, but when it does this it throws a code and temporarily disables VSC which means body roll itself will not fire the VSC system.

 

Yes my truck is a 2016 SR base 2.7l 5spd. I dont recall but for some reason i thought it had 265/70/16 when i got it certified preowned. I immediatly threw the same size on but my own wheels and all terrains. The factory sticker shows 245/75/16.

Here is a series of better to read from techstream. This is only just driving circles in the parkinglot or turning from a side street into traffic and only when i noticed codes going off. It doesnt show the turning into a steep parkinglot not straight and it fully engaging the traction control breaks or turning and accidentally hitting a curb that engaged the breaks. The other one would be driving down a tight windy road at 40 and the light flashing and thats not even at 90 degree steering angle. If i went 30mph (which is actually the speed limit just before going up to 45) it didnt engage.

 

Update on some stuff I've figured out. The "steering angle value" and "yaw rate value" are the net measured values used by the systems after correcting the raw sensor values by the zero offset and possibly some other filtering. The disagreement of the "sensor" and the "value" in techstream snapshots is due to the terribly slow update rate.

 

I have had the VSC light come on and shuttering during a slow uphill right turn in a completely stock 2020 off road will see what dealer says when I can get an appointment.

 

Dealer could not make the light come on so I sent them a video of it and am waiting for the Service Manager to reply will let you know what they say.

 

Bummer yeah that usually seems to happen that way. Let’s just hope they give some news to you. I’m installing UCA this weekend to get the alignment where it should for lifted trucks and hoping that fixes mine

 

Met with the service manager and he explained the Hill Start Assist function I thought it was for Manual trans only felt like an idiot but all good now.

 

Hmmm that doesn’t sound right to me. I mean I am a manual and the hill start assist just applies the brakes for a short time while on the hill. Just enough time to go from the break to the gas without rolling back. Shouldn’t trigger vsc light

 

Looked in the owners manual and it does show the VCS light will light up

 

Interesting. Before the lift i drove the truck for a year without having that light kick on when i started on hills. But whos to say. My specific deal also seems to be an odd scenario.

 

Little update.
Just got home from 4 wheel parts after installing SPC uca at 4 degrees of caster. They tested before and after. I tested making lots of left and right turns. Normal accelerating and hard. Pulled into parking lots that I knew engaged my brakes and even heard the tires try and break traction. The only time I got the light to flash was in a parking lot with the wheel almost full crank and accelerating like 10mph. Tight circles which isn’t normal conditions. Huge improvement. It does feel more stable driving, less wander

 

Update 2.0,
Only lasted a day. So about 50 percent of the time it will kick off the light now. So far haven’t noticed a loss in power when it does kick the light off. When I turn left into my parking lot nothing happens but when I turn right it fully engages the traction control breaks like I’m slipping.

 

Your steering angle for the resulting yaw rate still isn't agreeing and you're still overlooking the easiest pieces of hardware that should be inspected because they'll create this discrepancy.

 

Yeah i still havnt gotten down there to have someone turn it while im under. But woulda assumed that the 2nd alignment and then the 3rd once i replaced upper control arms woulda found anything loose in the steering rack. It does almost seem like the lights will go off later in the drive and only about half the time maybe less now. I'm not sure how much me having not changed diff/tranny/transfer case oils plays into account. I'm 10k past the 30k maintenance.