Traction control problem (I think)

[ShottsUZJ100]

I'm not sure why you thought I was pointing at you, but I wasn't.

My appologies!

 

[MoJ]

I think it should be acknowledged that MoJ was right, albeit for the wrong reasons, when they opposed pulling the ABS fuse.

No, I think I had the right reason as originally stated: Trouble shooting over the internet and then telling someone to disable a safety system is not a good practice.

Either way it will be interesting to learn what the root cause is.

 

[-Spike-]

Spike: The brake booster is electric powered. That's why it's safer so if you lose gas or ignition you have 100% stopping power. Without juice it will run out eventually. Maybe I should have warned you of this. Sorry.

You may think it's safer, but every other vehicle I've ever had still had brakes without the engine running. Not boosted, but useable. The brakes on this particular 100 were not useable without electricity. Not safer, IMHO.

-Spike

 

[Texasoil]

if the LC-100 brake system is designed such that loss of electrically powered boost results in NO brakes--that doesn't seem right. How would that get by the safety guys at DOT and NHTSA? Lots of vehicles, particularly medium/heavy duty gasoline engined trucks rely on electrical powered hydraulic boosters since there may not be any manifold vacuum (to power a vacuum booster) for very long periods of time.

Best redundancy is the old Citroen system--it had mechanical pump, master accumulator, brake accumulator/priority valve(switching everything to brake system if main pressure dropped) AND then the vehicle weight would 'back-feed' into the brakes to give about 50% of maximum braking.

How could someone be so DUMB as to drive this dangerous vehicle until it is properly sorted out. It should be trailered to the Dealer. Lawyers would have a field day with this one ' She KNEW th vehicle was broken, the warning lights had worked, and yet she CHOSE to drive this crippled vehicle, resulting in injury/death to (xxxx), therefore our policy coverage is null and void since it specifically excluded willful law violations [driving such a vehicle is called 'reckless driving']. And the charge is 2nd degree homicide since she KNEW it was unsafe.

 

[Atticus]

if the LC-100 brake system is designed such that loss of electrically powered boost results in NO brakes--that doesn't seem right. How would that get by the safety guys at DOT and NHTSA? Lots of vehicles, particularly medium/heavy duty gasoline engined trucks rely on electrical powered hydraulic boosters since there may not be any manifold vacuum (to power a vacuum booster) for very long periods of time.

Best redundancy is the old Citroen system--it had mechanical pump, master accumulator, brake accumulator/priority valve(switching everything to brake system if main pressure dropped) AND then the vehicle weight would 'back-feed' into the brakes to give about 50% of maximum braking.

How could someone be so DUMB as to drive this dangerous vehicle until it is properly sorted out. It should be trailered to the Dealer. Lawyers would have a field day with this one ' She KNEW th vehicle was broken, the warning lights had worked, and yet she CHOSE to drive this crippled vehicle, resulting in injury/death to (xxxx), therefore our policy coverage is null and void since it specifically excluded willful law violations [driving such a vehicle is called 'reckless driving']. And the charge is 2nd degree homicide since she KNEW it was unsafe.

lol. Thanks for the analysis, counselor.

 

[Jim_Chow]

I took a look in the electrical FSM. It shows the ABS/VSC/TRAC/Brake Assist are comprised of 8 ECU's. There is a fail safe mode for the brakes. It will feel like you have no brakes, but you actually do. It's just that you only have pressure at the front calipers, and it's greatly reduced compared to when the booster is operating (we're talking you have to apply a lot of pedal pressure to stop as the master cylinder sans booster is all you have; the amount of pedal pressure vs hydraulic pressure are outlines in the FSM). The rear calipers are entirely powered by the booster so you get 0 psi back there. The ABS/VSC/TRAC/BA functions are all intertwined in that you can't really disable one other than, say, VSC/TRAC by manipulating the CDL/t-case inputs.

Okay, I found the brake caliper pressure table....page BR-39, Lexus 2003 FSM, vol2:

When booster does not operate:
At 55 ft-lb pedal pressure:
front brake pressure: 391+ psi
rear pressure: 0 psi

At 77 ft-lb pedal pressure:
front pressure: 568+ psi
rear: 0 psi

When booster is operating:
At 11 ft-lb pedal pressure:
front: 234-405 psi
rear: 249-419 psi

At 22 ft-lb pedal pressure:
front: 639-809 psi
rear: 668-839 psi

At 33 ft-lb pedal pressure:
front: 1043-1214 psi
rear: 1088-1259 psi

At 44 ft-lb:
front: 1434-1604 psi
rear: 1501-1671 psi

So notice that in "fail safe" mode when the booster is not on, if you apply 77 ft-lb of pressure, you get very little braking power, and only at the front calipers.

 

[richg]

UPDATE: DO NOT REMOVE THE ABS FUSES and drive the truck, and DO NOT IGNORE warning tones.
Called the friend and asked her to come by the house. I removed the 40 and 50 amp fuses under the hood labelled ABS 1 and 2.

Spike-

I apologize for not remembering that there were two fuses labeled ABS on the 100 series. I had thought the hydraulic booster pump was labeled differently. In order to disable ABS operation but keep the hydraulic pump in operation, only remove ABS 1. This disables the solenoids.

As you were theorizing, you could also remove the abs solenoid relay (or just about anything else except remove power to the hydraulic motor) and you would go into the failsafe of normal boosted non-ABS braking.

Rich

 

[ShottsUZJ100]

You may think it's safer, but every other vehicle I've ever had still had brakes without the engine running. Not boosted, but useable. The brakes on this particular 100 were not useable without electricity. Not safer, IMHO.

-Spike

If you learn more about the system you'll see why these are expanding out to other models.

 

[-Spike-]

richg- thanks for the correction, it may come in handy depending on what the dealer says tomorrow.

Jim_Chow, that's... enlightening. And kinda scary. I was hoping to find out that this particular truck had no brakes due to a malfunction, but it seems it may have been operating as intended.

Shotts- manufacturers expand features to other models because they work- for the manufacturer's purpose. I'm desperately restraining myself from having another arguement with you about 'features' of the 100. Honestly, I don't know enough about the 100 to have an intelligent discussion about them just yet- but I will soon. Right now, I just want to help a friend, not bore or aggravate an entire forum population. We can have a good arguement on the next trail, as soon as I get my gears done. Heck, it's winter, I'll probably head south for a couple of trails while it's relatively cool, so I'll be in your neighborhood! Keep me in mind if you plan any cool runs worth the couple hour's drive.

-Spike

 

[dclee]

If you learn more about the system you'll see why these are expanding out to other models.

Based on Jim's post, I find it hard to believe that this braking setup is a "good" thing. Let's see, lose electricity (say a short, cut wire, blown fuse/relay), and get ZERO pressure to the rear brakes? Please, oh please tell me how this is a "good" design?

 

[ShottsUZJ100]

Based on Jim's post, I find it hard to believe that this braking setup is a "good" thing. Let's see, lose electricity (say a short, cut wire, blown fuse/relay), and get ZERO pressure to the rear brakes? Please, oh please tell me how this is a "good" design?

You are a smart guy. You can think of MANY situations where 100% braking could come in handy when the engine is not running or has died. Don't insult your intelligence.

 

[dclee]

You are a smart guy. You can think of MANY situations where 100% braking could come in handy when the engine is not running or has died. Don't insult your intelligence.

Hey John, you are about the LAST person who should be making cracks about people's intelligence, however subtle...

And, to be honest, not really. Unless the engine dies on a steep downhill at freeway speeds (and when's the last time that ever happened to a Toyota engine?), at least I'd still have braking, even if unassisted. However, think about the same situation when the relay blew (admittedly just a unlikely). A MUCH more dangerous situation IMHO.

 

[ShottsUZJ100]

Hey John, you are about the LAST person who should be making cracks about people's intelligence, however subtle...

And, to be honest, not really. Unless the engine dies on a steep downhill at freeway speeds (and when's the last time that ever happened to a Toyota engine?), at least I'd still have braking, even if unassisted. However, think about the same situation when the relay blew (admittedly just a unlikely). A MUCH more dangerous situation IMHO.

Whatever. Go ask Toyota engineers then.

 

[dclee]

Whatever. Go ask Toyota engineers then.

The same engineers who designed the, as you put it, horribly unsafe brakes on the 80 Series? Can't have it both ways Gomer!

BTW, that's such a terribly insightful response: "Go ask the Toyota engineers then."

 

[-Spike-]

The dealer checked it out and said one of the wheel sensors was sending bad info. They reset the computer, and that's supposedly the fix for it. I hope it works. That and the vehicle inspection cost her $95. On the good side, they gave her '00 with 160K a clean bill of health and a short list of maintenance items that she is due for. I'll be back in the next few weeks for help on her timing belt and maintenance stuff- although if it's all covered (I'm sure it is) I'll find what I need quietly.

Thanks again for the help, guys.

-Spike

 

[ShottsUZJ100]

The same engineers who designed the, as you put it, horribly unsafe brakes on the 80 Series? Can't have it both ways Gomer!

BTW, that's such a terribly insightful response: "Go ask the Toyota engineers then."

I wanted to put you in touch with someone of your same level.

 

[richg]

The dealer checked it out and said one of the wheel sensors was sending bad info. They reset the computer, and that's supposedly the fix for it. I hope it works. That and the vehicle inspection cost her $95. On the good side, they gave her '00 with 160K a clean bill of health and a short list of maintenance items that she is due for. I'll be back in the next few weeks for help on her timing belt and maintenance stuff- although if it's all covered (I'm sure it is) I'll find what I need quietly.

Thanks again for the help, guys.

-Spike

So they didn't even replace the wheel sensor that was sending the "bad info"?

As for the t-belt and water pump, there are a few threads on here with tips and info on doing one. I've made a few posts myself on them as well.

rich

 

[-Spike-]

Nope, supposedly the fix for the problem was to reset the system. I wasn't there- if I were, I'd have been asking questions at that point. Unfortunately the only way to know if it's fixed is for the problem not to resurface- and if it does, to pray that it's not catastrophic this time. But, what can I do? The dealer has spoken, and I have no resources to prove them wrong.

-Spike

 

[gray]

Perhaps I might have said it in a nicer fashion.

But to "not have time" to protect your own children strikes me as being equally unthinkable.

If 3 members have an issue, I'll edit the post.

No issue here;
I agree; hardcore statement, but that is why some people
pass on their genes, and some don't.

It is called stupidity.

If this happened to my wife and kids, I would have the car towed
to the nearest Toyota dealer. immediately; and would get her a rental to drive until it was fixed; period.

g

 

[ShottsUZJ100]

Nope, supposedly the fix for the problem was to reset the system. I wasn't there- if I were, I'd have been asking questions at that point. Unfortunately the only way to know if it's fixed is for the problem not to resurface- and if it does, to pray that it's not catastrophic this time. But, what can I do? The dealer has spoken, and I have no resources to prove them wrong.

-Spike

Is all still well with that truck?