Does ECU Upgrade Fix 04/05 Traction Control?

yes, that's the one.

the differential in the prius isn't equipped to do this- it takes a special limited slip differential (for instance, they put one in the fj cruiser). sure there's some programming differences, but the hardware is what provides the functionality of allowing the non-spinning wheel to get power. the differential in the prius is not physically equipped to do that.

i don't know what happened to TP's car then, since he got a new engine ecu which isn't related to the trac at all. i'm assuming he eventually got the hv flash, in which case that's the same thing that your car got.

ok, so you got the new engine ecu then... and did he eventually reflash the hv?

are you absolutely positive that nothing else changed that could affect the trac? because the only difference i'm seeing here that would affect trac is that you got the hv ecu reflash, if they did it in the end. (the engine ecu is irrelevant here.) but nyprius had the same thing, so your cars should be no different software-wise.

oh there are ways to disable it, but you can burn up your mg's real quick that way and then you're out a car.

well as far as even the dealer knows, there is none. and warranty won't cover anecdotal evidence, trust me on that. even if the 06 ecu had no wiring/pin position changes, (which it likely does, they did a lot of rewiring that year) they wouldn't stick an 06 ecu in there if it wasn't the same as the 04/05.

 

Hard to believe that yet another one of these threads is going
back and forth this long. History repeats itself.
.
For those claiming that the car slides backwards on an attempt
to move forward, has anyone actually taken note of which direction
the wheels are ROTATING, whether they're actually applying any
meaningful force against the road or not? Does anyone honestly
think that the car placed in "D" would apply reverse-direction
torque to the axles?
.
And let's keep one important thing in mind: "allowing the wheels
to spin" is a meaningless concept, because on of the major jobs of
the HV ECU is to keep exact, moment-to-moment track of where
both MGs are and how much current to apply to which windings. It's
not like the ECU turns on a switch and lets fly on a self-running
motor -- no, it is integrally involved with making every small bit
of rotation happen or not happen. Remember that big rack of
power transistors? The ECU is controlling that every step of the
way, and by implication knows exactly how fast each component
is turning and how fast it is willing to let it turn [i.e. by
applying a given amount of torque via motor winding current].
.
And also for the record, "limited slip" in this case is done via
tight integration with the braking system, not anything inside
the transaxle itself. It's not like the traditional "posi rear".
.
_H*

 

Agreed on the symptom. Read this for my own negative-progress
experience, in fact. But that's simply because the wheels trying
to turn forward broke static friction and allowed the car to
slide backwards down the hill. The car never *gave up* trying
to move forward, it was just in unsurmountable circumstances.
.
_H*

 

I have had similiar experiences with TC on my 2005, as I commuted daily from Salt Lake City to Park City, up Parley's Canyon.
I have ICE-X tires and never experienced a problem even in heavy snow; in fact, in very heavy snow, I usually went up the canyon early, before snow plows or the morning rush hour. Here's the reason why: when I got behind four overlapping snow plows, the traffic backed up and invariably someone was in front of me that didn't have good snow tires slowing the average speed to 15 mph or less... Parley's canyon is 10 miles long and very steep in places.... I found out the 1st year I had the car that there is a self-fulfilled prophesy with TC... below 15 mph and occassionaly letting up on the pedal, on a steep slippery road, the TC will continue to slip until you get to 7 mph and you have no hope to recover, in traffic.
I finally solved my problem... I found another job.. I would not give up my car.....
steve

 

I don't think the Prius Trac makes use of the brakes at all. For example, on the "all season" tires, if the right wheel is on ice and the left wheel is on dry pavement - a common occurrence around here before we're allowed to put on the studded tires, the car doesn't move. Period.

With my FJ, it has electric assist power brakes with 4 channel ABS integrated into the Trac. In the same situation as above, there is a buzzing sound and vibration, similar to the Prius when you first press the brake pedal to power on.

The brake is being applied to the spinning right rear tire and away you go. If I really floor it, the left rear tire on dry pavement will chirp, then the Trac will regulate engine torque to prevent a burnout

I have the 2007 FJ shop manual in PDF, but for some reason my attachment privileges are revoked. There is an excellent article on how the speed sensor, ABS motor, and electronic throttle are integrated to provide "real" traction control

 

I have purposely tried to get my FJ stuck at my hobby farm. It never kills all the power, and in 2H the brakes are alternately applied to the left rear and right rear tires when they are freely spinning in deep snow. So the system is clearly trying to find a tire with more traction

In that case, I can just shift into 4L, poke the Diff Lock button, and back out

Since you're a moderator, any chance of restoring my uploading privileges? I'm apparently not allowed to upload any PDF's, and my max JPG upload is 19 KB. Did I upset somebody recently??

I would like to upload an approx 500 KB PDF from the FJ shop manual that explains how the ABS, Trac, and A-Trac are all integrated. For example, in 2H if a rear wheel spins, the brake is applied and if the wheel is still spinning, engine power is reduced.

In 4L, A-Trac can do the same trick for both axles. Say you're crossing a deep ditch and one or two wheels leave the ground, the brakes are applied to those wheels and the two wheels on ground can still try to drive you forward

There is no reason that I can determine for the Prius to not be able to integrate the brakes, to apply the brake to the spinning tire. This would transfer torque to the other tire. Many cars out there - both front wheel drive and rear wheel drive - have such a Trac system

In many cases, the traction problem is worse when just one wheel is on a slippery surface. To be able to transfer torque to the other wheel would solve 90% of the issue.

 

Nope, no clutch pack in my FJ. In normal driving - 2H or 4H - my FJ rear differential operates as an "open" differential. The full time electronic traction control - Trac - uses the ABS speed sensors at each wheel to determine if rear wheel spin is evident

Say I'm in 2H and thanks to our recent winter weather, the right rear tire is sitting on snow/ice and the left rear tire is sitting on fairly clean pavement. The light turns green and I step on the gas pedal. The FJ has a lot of torque so even with the winter tires, the right rear tire wants to spin

The FJ senses this and there is a buzzing sound and vibration, similar to when you press the Prius brake pedal to power on. The FJ also has electric assist power brakes. The buzzing sensation is the electric assist pump applying the brake to the right rear tire, forcing torque transfer to the left rear tire.

If I really floor it, then engine power is reduced. The FJ has a "timeout" feature where if you're in really bad conditions, there is the possibility of overheating the brakes by continuous Trac application. In that case, a buzzer sounds in the dash, the Trac warning lamp blinks, and the system is disabled.

In 4L, poking the A-TRAC button applies four wheel electronic traction control. You can cross a berm or a ditch and have one wheel on each axle just in the air, the brakes are applied to those wheels and the wheels still on the ground can drive you forward

As another option, in 4L I can poke the Diff Lock button. That commands an electric shift motor in the rear axle to move a shift fork, which forces a splined collar into the case and locks both axle shafts together

There really isn't anything special about my FJ. It's priced far cheaper than a 4Runner, at least here in Canada, with all these electronic goodies.

I'm really curious why the Prius Trac couldn't have implemented the same "apply brake and reduce torque" sequence that works so well on my FJ?

What I find really curious is that my FJ can combine various electronic and mechanical traction aids, and they work so well together.

 

hmm. he didn't recall it that way. they're such good vehicles that DH didn't have a lot of chance to tinker around with them.

he must have been thinking the 4runner, in that case it looks like new toyotas may be starting to switch over to the electronic trac then. the trucks previously used just the limited slip differential.

but this is just trucks.

if they're beginning now to implement an electronic trac system, they may be able to put one in the prius in the future.

 

we are aware of the way to do that, but DH was not comfortable posting it for general use...

 

It might be a good idea, after posting how to turn off TC, to also post how to turn it back on.

EDIT: I cross-posted with nyprius, who answered the question.

 

Close. My FJ will first apply the brake to the spinning rear wheel, then reduce engine torque. Actually, it works so transparently and so well, I'm never aware of it. I really have to pay attention to even realize it's working

We had some freezing rain last night. I actually prefer -30 C and colder, just to avoid slippery conditions. Anyhoo went to the grocery store early this am to stock up on things for the xmas trip out to the hobby farm.

First went in the Prius, and with the studded tires it wasn't too terrible. However, ice at one intersection confused it. Forgot something and drove back with the FJ. Left it in 2H and never had an issue

Note: if I really plant the gas pedal, the FJ does allow minor wheelspin and some tail waggle on ice. The Trac also is engaged - but "detuned" - in 4H. If I floor it in 4H, crazy things happen (rather quick donuts, sort of like that scene in THX 1138 when THX floors the jet car in the tunnel)

I guess I shouldn't compare the Trac in my FJ to the Trac in my Prius. It tends to make me very disappointed in how the Prius Trac was implemented. Yes, I understand it was to protect the HSD components, but they could have provided an override button to allow low-speed traction

So the +2005 Prius cars have a "real" Trac system? I wasn't aware of that. I have been thinking of getting a 2008 Prius, perhaps I should test drive one to determine if the Trac has been changed

They certainly are priced more reasonably now in Canada. Same "B" options as mine are now a good $5,000 cheaper.

Gotcha.

Happy holidays, will try to check in from the hobby farm. Finally had the satellite internet system installed in October