Here's my "gut":
The TRAC/VSC/ABS systems have been so reliable.....my guess is it's something mechanical causing the system to kick in. What? Have no idea. End "gut".
Traction control problem (I think)
- Thread starter -Spike-
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Here's my "gut":
The TRAC/VSC/ABS systems have been so reliable.....my guess is it's something mechanical causing the system to kick in. What? Have no idea. End "gut".
Second this, but agree with everyone else, the truck should not be driven further until the problem is diagnosed and repair. It is an accident waiting to happen.
Please tell me what failure (other than one in the VSC system itself) would cause the VSC system to become active while cruising on a straight road without the brakes applied in perfect weather? Now remember, not once has it gone off while driving around curves, and the vehicle performs normally otherwise. I don't believe the VSC is saving anyone in this case. I believe it is the culprit.
Shotts' experience is due to the fact without the shock properly installed, steering angles above the VSC threshold were required for a given vehicle rotation at a given speed, so the VSC kicked in so that the truck would rotate properly and Shotts didn't spin out or go flying off the road.
None of us can ever be certain of anything through this forum. But based upon the information presented, if you gotta drive the truck to the dealer or wherever, in my opinion, the safest way to do that is with the ABS fuse pulled.
rich
Yes sir. I'd be freaking!
No we cannot be certain.
What could make a perfectly normal VSC system kick in?
A bad bearing, a bad sensor or hung brake (or other) component causing a varience at one wheel? There are many possibilities.
When I had my rear axle rebuilt this year they kept it another day because they botched a wheel sensor upon re-install. What if somebody else wouldhave just thrown it in and prayed?
If I was a gambler my money is on mechanics and not the VSC/TRAC CPU system. Could be DEAD WRONG though.
MoJ
Moderator
Certainly, pretty much any failing mechanical or non-VSC related electrical component that could affect wheel speed. System senses an issue with wheel speed and then reacts accordingly to compensate. If this were the case then disabling the system would be detrimental.
- Thread starter
- #47
Although I also asked for opinions on what might be wrong, my immediate concern was and is to find a way to disable the system. In my mind it's the only system that could cause the symptoms as they were described to me. I don't see driving a vehicle with the ABS/ traction control disabled as being unsafe, it's just not as safe as it could be. (I'm sure people are gonna take offense with that statement, but that's my opinion.) If anyone has reservations about the advice I've been given, please keep in mind that I asked for it, and I'm a reasonably responsible adult who can make his own decisions and has some mechanical knowledge.
Shotts, everything from the wheel sensors to the brakes to the 'VSC/TRAC CPU' is part of the system. Something along the line is malfunctioning, whether it be the CPU or a loose shock. The symptoms don't point to or away from anything- it could easily be a bad/broken/dirty wheel sensor or a bug that decided to die on the circuit board of the CPU and shorted something. All I know is that the system is activating when it shouldn't be.
My secondary reason for posting the whole problem in this forum was to find out if it were a known issue, which would probably make diagnosis much easier. Apparently it isn't, and I don't expect anyone to be able to diagnose a unique problem like this over the internet. I appreciate the various suggestions given and welcome any new ones, and if I get the truck in my shop and have any trouble figuring it out I'll get back with you guys.
-Spike
Shotts, everything from the wheel sensors to the brakes to the 'VSC/TRAC CPU' is part of the system. Something along the line is malfunctioning, whether it be the CPU or a loose shock. The symptoms don't point to or away from anything- it could easily be a bad/broken/dirty wheel sensor or a bug that decided to die on the circuit board of the CPU and shorted something. All I know is that the system is activating when it shouldn't be.
My secondary reason for posting the whole problem in this forum was to find out if it were a known issue, which would probably make diagnosis much easier. Apparently it isn't, and I don't expect anyone to be able to diagnose a unique problem like this over the internet. I appreciate the various suggestions given and welcome any new ones, and if I get the truck in my shop and have any trouble figuring it out I'll get back with you guys.
-Spike
- Thread starter
- #48
The only possible scenario I can think of that would satisfy those conditions would be a wheel locking up, then the traction control compensating for it and keeping the truck under control. I think I can safely rule that out. Having the brakes randomly apply themselves seems to be much more dangerous than losing a system that isn't necessary for driving. Pulling the brake pads to fix a grinding sound would be bad, but not shutting down the ABS/ traction control system. IMHO.
I'll be talking her through pulling the ABS fuse, as soon as she 'finds the time'.
-Spike
What exactly is a non-VSC related electrical component that could cause the failure? Wheel speeds sensors, accelerometers, steering angle sensors, brake input sensors, are all part of the VSC system.
As for something mechanical, remember while cruising on dry pavement, all the wheels are rotating on the pavement at the same speed. You'd have to be dragging one to cause a wheel speed sensor differential which takes A LOT of braking force. So again, give me an example of a mechanical failure that happens randomly in this situation, yet can magically fix itself an instant later and leave no other indications of any sort of problem?
Brake hung up? No mention of vehicle pulling to the side UNTIL the system kicks in. No grinding noises, no smoking wheel wells, no stinking smells mentioned. And it isn't going to fix itself!
Bad bearing? If the bearing is destroyed enough such that it can stop the wheel from rotating, I have a feeling you're going to hear some really ugly noises long before a bearing is able to lock a wheel up. And it isn't going to fix itself!
Drivetrain? Again, you're going to hear alot of ugly noises before anything else happens. And it isn't going to fix itself!
Steering/Suspension? I'd wager if it was a failure in one of these parts, it would surface itself under steering/cornering applications much more than straightline, exactly as shotts experienced.
Including after adding N74L shocks.
Holy s#!t, John managed to get the N74L shocks into this conversation! I am truly awed...
- Thread starter
- #51
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. Then went inside to talk to her. Lost track of the time and realized it was time to go pick up my daughter at day care, like right now. Knowing I needed to test drive her truck before sending her on her merry way, I asked for her keys and left her there for the quick (300 yard) drive to the day care. Truck drove fine; ABS, TRAC OFF and TRAC lights on. Picked up daughter and on the way back to the house I decided to stress the system just a little to see what it would do without ABS. Stopped fine the first time, so being who I am I hit the brakes again. Truck stopped, but more force was necessary. Odd. Started moving and the warning tone sounded. Not being familiar with the vehicle, I thought it might be the seatbelt chime, so I hit the brakes to stop and put it on. Houston, we have a problem- very little braking. By now I'm 100 feet from the house so I parked it there and went in to break the news to her that I was gonna have to spend a little time figuring this out- without my daughter in the truck.
Took the truck out again in the neighborhood. The warning tone was gone when I started the truck. It returned immediately upon braking, and the brakes still weren't functioning and getting progressively worse. I pulled over, replaced the fuses, and restarted the truck. Warning tone still there, idiot lights still on, no brakes at first, but after a few applications they came back and the tone and lights went off. I test drove it a bit more, took it back to the owner and made an appointment for Monday morning at the local dealer for her (they were booked solid through the weekend). I impressed upon her the danger she was in if she drove it, and she said 'I guess that I shouldn't drive it to Prescott Sunday then'. No, no road trips. She told me that every time it had acted up it was moving at over 50 MPH, and that she would keep it well below that on the way home and to the dealership on Monday.
While replacing the fuses I saw that there are a couple of relays for ABS SEN and ABS MOTOR 1 & 2. I thought about pulling these one at a time to see if there was a safe way to disable the system, but it looked like I would need a tool to remove the relays, and I didn't want to be responsible for some other side effect down the road.
I hope that this behavior is a symptom of the problem. I would hate to think that a car would lose its brakes if it blew a couple of fuses (or one, for all I know). If that's part of the design it's complete bull**** and I will never own a 100. I have serious problems with the steering and braking systems not being operational by mechanical means. Steering and braking by wire are not acceptable in my opinion. The driver should always have control of these two systems no matter what electrical systems are malfunctioning. The brakes on her car completely failed, and I had to resort to the emergency brake at less than 10 MPH to stop it. Granted, now I know if I hear that warning tone I need to get off the road immediately, but the average person probably won't. In any case, hopefully with the problem corrected the brakes won't behave this way, but I'm very disconcerted that the brakes are not functional without the electrical systems intact.
FWIW when I described the problem to the dealer service phone guy his first response was 'Sounds like the ABS is acting up'. I asked him if this was a common thing, and he said 'We don't see any problems at all on those Land Cruisers, it sounds strange'. I'll keep you all posted on what they find.
-Spike
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. Then went inside to talk to her. Lost track of the time and realized it was time to go pick up my daughter at day care, like right now. Knowing I needed to test drive her truck before sending her on her merry way, I asked for her keys and left her there for the quick (300 yard) drive to the day care. Truck drove fine; ABS, TRAC OFF and TRAC lights on. Picked up daughter and on the way back to the house I decided to stress the system just a little to see what it would do without ABS. Stopped fine the first time, so being who I am I hit the brakes again. Truck stopped, but more force was necessary. Odd. Started moving and the warning tone sounded. Not being familiar with the vehicle, I thought it might be the seatbelt chime, so I hit the brakes to stop and put it on. Houston, we have a problem- very little braking. By now I'm 100 feet from the house so I parked it there and went in to break the news to her that I was gonna have to spend a little time figuring this out- without my daughter in the truck.
Took the truck out again in the neighborhood. The warning tone was gone when I started the truck. It returned immediately upon braking, and the brakes still weren't functioning and getting progressively worse. I pulled over, replaced the fuses, and restarted the truck. Warning tone still there, idiot lights still on, no brakes at first, but after a few applications they came back and the tone and lights went off. I test drove it a bit more, took it back to the owner and made an appointment for Monday morning at the local dealer for her (they were booked solid through the weekend). I impressed upon her the danger she was in if she drove it, and she said 'I guess that I shouldn't drive it to Prescott Sunday then'. No, no road trips. She told me that every time it had acted up it was moving at over 50 MPH, and that she would keep it well below that on the way home and to the dealership on Monday.
While replacing the fuses I saw that there are a couple of relays for ABS SEN and ABS MOTOR 1 & 2. I thought about pulling these one at a time to see if there was a safe way to disable the system, but it looked like I would need a tool to remove the relays, and I didn't want to be responsible for some other side effect down the road.
I hope that this behavior is a symptom of the problem. I would hate to think that a car would lose its brakes if it blew a couple of fuses (or one, for all I know). If that's part of the design it's complete bull**** and I will never own a 100. I have serious problems with the steering and braking systems not being operational by mechanical means. Steering and braking by wire are not acceptable in my opinion. The driver should always have control of these two systems no matter what electrical systems are malfunctioning. The brakes on her car completely failed, and I had to resort to the emergency brake at less than 10 MPH to stop it. Granted, now I know if I hear that warning tone I need to get off the road immediately, but the average person probably won't. In any case, hopefully with the problem corrected the brakes won't behave this way, but I'm very disconcerted that the brakes are not functional without the electrical systems intact.
FWIW when I described the problem to the dealer service phone guy his first response was 'Sounds like the ABS is acting up'. I asked him if this was a common thing, and he said 'We don't see any problems at all on those Land Cruisers, it sounds strange'. I'll keep you all posted on what they find.
-Spike
I think it should be acknowledged that MoJ was right, albeit for the wrong reasons, when they opposed pulling the ABS fuse.
With the decision making this friend of Spikes has previously exhibited, I have no trouble envisioning her pulling that fuse and then getting straight onto the highway, where the issue Spike discovered would have also put her in danger.
Well, now we all know - disabling a safety system that (as far as we know) only ADDS to the overall safety of the vehicle without being a CRITICAL safety gadget - may not be the wisest option.
We all thought the ABS system rode transparently on top of the brake system, but we (Spike) discovered it is an integral part of that system.
... and that's one to grow on...
-LX Pilot
With the decision making this friend of Spikes has previously exhibited, I have no trouble envisioning her pulling that fuse and then getting straight onto the highway, where the issue Spike discovered would have also put her in danger.
Well, now we all know - disabling a safety system that (as far as we know) only ADDS to the overall safety of the vehicle without being a CRITICAL safety gadget - may not be the wisest option.
We all thought the ABS system rode transparently on top of the brake system, but we (Spike) discovered it is an integral part of that system.
... and that's one to grow on...
-LX Pilot
Actually, we still don't know what happened, or if pulling the fuse is what caused this problem.
On the whole, yes, we still don't know what happened.
However, loss of the brake system was not a previously reported symptom - having its first occurrence only after Spike pulled the fuses.
However, loss of the brake system was not a previously reported symptom - having its first occurrence only after Spike pulled the fuses.
Post hoc ergo propter hoc.
Ah....If you're pointing at me, I never suggested diabling it. No spin dude.
I did support Spike's idea though to disable it. Good thing he tested it. I would have too had I done the same.
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.
Bottom line isn't that the 100 is a dangerous POC. On the contrary....it's far safer than other Cruisers. When a warning light comes on....like ABS...the driver should not drive it. Your test proved it.
Ok, Bartlett -
You spring a bloody nose for no apparent reason, it just starts dripping blood.
In trying to effect a remedy, I punch you in the nose - lets just say the blood flow stays the same.
Now your nose hurts, but it didn't hurt before I punched it.
Your nose hurts after I punch it, therefore it hurts because I punched it.
The hurting is unrelated to the bleeding.
-----
The brakes went out completely AFTER Spike pulled the fuses.
The brakes had not gone out completely before this.
ERGO - the brakes went out completely because the fuses had been pulled.
To our knowledge, this was unrelated to the original issue.
NOW - I'm not saying that should be the end of it - I was saying, however, that MoJ's cautioning against pulling the fuses, in this instance, turned out to be correct.
After they figure out the original problem, it would be interesting to pull them again and see what happens - unless one of us wants to try it....
....
....
NOT IT!
-LX Pilot
That would be the test one would have to perform to KNOW that the pulling of the fuses resulted in the loss of brake power, although, if Shotts' explanation is correct, you would be right (but for reasons not resulting from the logical exercise of analyzing one event following another). Anyway, you're probably right, but I've basically been at work for 48 straight hours so I'm getting a little snotty.
