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Brake Warning pops up on the display!


HERO Maker
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OK, if I weren't putting in 450 plus miles per day, maybe things wouldn't start acting up with my truck!!

Just about 30 minutes before reaching Howe, IN today, we had a warning flash on the display and it left a small picture of the engine brakes on the lower bar light area. I switched the brakes off, and it quit, but did come back on just a minute later! Put the brakes back on and it came on in about 30 seconds and then went off and then came on again, and again.

 

The display reads that I need to checks brakes at the next stop.

 

I'm thinking I've got one of the electric gremlins running around, or maybe I've got a problem with the air hose for the engine brakes. Or just now thought maybe it has something to do with the clutch switch that gave be problems for engaging my PTO?!!

 

Any ideas? It's a yellow warning light, not a red stop now light.

 

Thanks guys,

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This is what the Owner's Manual says about the display:

Too Cold for Engine Brake (Volvo Engine Only)
Position 2 of the engine brake should not
be switched on until the engine has become
warm (over 110F [45C]). If position 2 is
selected and the engine is too cold, this
symbol will be shown (however, VEB is
not activated).

 

I know that is not a lot of help bit might be a place to start.

 

Chet

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I had that issue on my '01. found the right rear ABS sensor connection was corroded. Cleaned it up and it has not happened since. But I drove with that warning on and off for 4,000 miles. It was a lot more frequent bob tail and almost never came up while hitched. Not that I think that had anything to do with a bad connection.

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Chet, it is that engine brake symbol. Didn't think I had ABS on mine. Does yours have it? I'm going to need to look a lot closer to mine in the morning.

 

On the road again tomorrow. Will see what happens. It was coming on and then would go off, and back on again, and then off.

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Yes, the Engine Brake tell tale looks just like the symbol on the Engine Brake Switch.

 

The ABS tell tale has "ABS" where the engine is in the brake tell tale and has a piece of a hood symbol to the left.

 

I have never observed the ABS tell tale on my Volvo. Here is what the OP Manual says about testing:

 

The ABS control unit contains a self-testing program that is engaged each time the ignition is turned on. The operator can verify the testing by listening for the ABS
modulator valves actuating twice in series. To increase the sound, hold down the foot brake pedal when the ignition is turned on. The self-test is not finished and the telltale
will stay on until the vehicle has started to move. The wheel speed sensors are tested when the vehicle starts to move. If they test OK, the telltale will go out at approximately
7 mph (11 km/h).

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Rocky,

I went to the Volvo and fired it up to check out the "ABS" test in the OP Manual.

 

First, the air pressure needs to be up before I noticed anything like a test.

After I aired it up, I shut it down and put my foot on the service brake.

1. With the key in the "on" position, the ABS light came on just ahead of all the other telltale lights.

2. After a couple of seconds, it indeed made some more noises as the truck tested the ABS. In fact, mine went through a series of three tests "modulator valves actuating twice in series".

3. After I started the truck (foot still on brake pedal), it went through another single series of the modulator valve actuations.

Something about the telltales for ABS and Engine Brake if it might help: The Engine Brake telltale shows up in the leftmost graphic display only when the ECU tells it to. The ABS shows up at the bottom of the center section. In normal ops, it just comes on with all the other telltales as part of the startup.

 

I learn more everyday!

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And Chet, you have taught me something today also.

Yes, my bad. Once I got down close the the warning, it does say ABS! ( I have to talk to my eye guy about that!)

I normally wait until I here the two clicks that might be what you are describing. I will talk a little longer tomorrow to pull out and walk thru that sequence.

 

Ron, no codes are being thrown, and that is what is confusing me. It did it again today. I just drove a few hundred miles, but it stopped after the the first 60 minutes!

 

We'll see whats up in the morning.

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ABS you say? I have been plagued by ABS since day one. On my truck, what happens is this:

 

You have a tone wheel on each ABS tire/wheel (with maybe the exception of the center axle). A Hall -Effect sensor which can be accessed on the inner outside of the brake backing plate looks at the tone wheel. The tone wheel is made up of evenly spaced depressions that look like gear teeth. As the tone wheel turns, the sensor counts the depressions between the gears. If the count does not agree with what the ABS computer thinks it should it assumes the wheel is sliding on the pavement and releases pressure to the brake on that wheel to stop the skid.

 

A while back I kept getting ABS codes out of the blue just like you described. I replaced sensors, checked modulator valves, wiring, ABS computer to no avail. Then I found the gremlin - rust deposits had formed between the teeth on the right front tone wheel. Since rust is iron oxide it is also magnetically conductive and the ABS sensor was not returning the right tooth count - therefore a false positive told the ABS computer the wheel was skidding. With the wheel and brake drum removed I gently brushed away the rust between the teeth of the tone wheel. Problem was solved. The guys at the Volvo shop I visit never mentioned this as being a possible issue.

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Hey there, Randy. Read your response to Rock as we're heading east on I-80 (just left the Giant Iowa Truck Stop about an hour ago!) He said, "Wow. Great. I appreciate the lesson from the Professor." He asked, "Is it always the right front or can it be any one of them?"

 

Thanks for the scoop. We will be in Colorado by Tuesday and I'm as seriously interested in braking power as HERO Maker is!

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FWIW - According to Volvo's ABS operations tech bulletins, if a count on one tone ring is off during any part of a continual "ABS Test" comparing the counts from the tone wheel, you ONLY lose ABS on that one wheel. You do not lose the entire ABS System. The wheel that flunked just will not have ABS - meaning you can lock-up that one wheel in a panic braking event or on a slick road - which is not a good feeling. The ABS error does not reset until you stop, turn off the ignition and start rolling again - if the counts sent to the ABS computer are what it expects, the light goes out and full ABS starts working again. If the count is off at any time while you are driving and not braking you may get the ABS fault code and light - this can happen at 10 miles or 1,000 miles into a trip. On my 2004, it does report which wheel, when the event occurred, number of times, etc. in the Driver Information Display when you run the fault codes from the stalk. Oh, one other tid-bit...... I received more frequent errors when it rained (tone wheel wet) than dry until I discovered the problem and removed the rust build up. Has it been raining? Now, if you should decide to jack up the wheel showing the error you can pull out the sensor from the backing plate with a small screwdriver blade and needle nose pliers and, by using a pen light to shine in the hole and holding your head at just the right angle, actually look at each tooth on the tone wheel as you rotate the tire. Using a stiff brush that fits in the hole, like a small acid brush with the bristles cut back to about 1/4", you might be able to clean away any rust deposits. When you put the sensor back in mount it inside the mounting/alignment sleeve or clip (unless the sleeve stayed in the hole), smear grease on the end of the sensor and push it all the way in as far as it will go inside the sleeve, then into the hole as far as the sleeve will allow - no other adjustment is needed. If it does not go all the way in you may get errors as well. The magnetic field is not strong enough to work if the sensor is pulled back too far.

 

I don't really expect you to be carrying an oscilloscope (I do - a small digital), but if by chance you should be able to snag one you can connect it where the sensor wire unplugs on the inside of the frame rail. With the scope connected you can actually see each pulse from the tone wheel as it passes the sensor. If a pulse or two drop out as you turn the wheel, most likely a problem with the tone wheel - not a sensor or the ABS computer.

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Just a thought and I haven't read the book. If I was an even count, what happens in turns when the outside front goes the farthest, inner front goes less, rears etc. Every tire having it's unique radius from the center of the turn? Thus, a different count.

 

Uneven tire diameter, say new steers, different count.

 

I'd have to guess there is a range of count, or difference in rate of change that would take other factors into account. Now say that your count is off by say 5% for longer than 15 seconds or one wheel, with brakes applied, sudden stop in relation to the others?

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ABS takes into consideration the wheel speed. It's when the ring gear doesn't move that the computer senses a locked wheel / skid, based on other criteria- camshaft speed sensor, transmission gear, last known speed vs rpm, etc.

Back in the dually days, the Dodge Ram had the same setup but it was in the differential itself. Problem was that the ring tooth gear that the sensor read would work itself off the back of ring gear (actual axle ring) and would either self-destruct or hopefully throw a code first. I had to pull the pumpkin twice- once under warranty, once on my own to press the ring tooth gear back on. The second time it was "permanently" attached.

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Just a thought and I haven't read the book. If I was an even count, what happens in turns when the outside front goes the farthest, inner front goes less, rears etc. Every tire having it's unique radius from the center of the turn? Thus, a different count.

 

Uneven tire diameter, say new steers, different count.

 

I'd have to guess there is a range of count, or difference in rate of change that would take other factors into account. Now say that your count is off by say 5% for longer than 15 seconds or one wheel, with brakes applied, sudden stop in relation to the others?

Bill,

My understanding, which is somewhat limited, is that as long as the count is consistent everything is hunkey-dory. It is when there is no count or a missing pulse from the tone ring that the ABS decides there is a problem. Since the tone ring is steel, it is subject to building up some rust. Rust, or iron oxide, which can be magnetically conductive and build up between the teeth of the tone ring can cause the hall-effect sensor that is looking at the ring to miss a count. I've watched it on an oscilloscope and its, well, like stopping a heart beat when it hits that spot. Crazy, I know, but it screws up the ABS.

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Sorry, that was a leading question - Socratic method of teaching? - questioning the statements. I've had to do as Jim has and replace tone rings, pickups, shield cable, etc. They run the pulses through an algorithm that allows 3-5 % deviation in the counts but there is also a time component to it. ie. one portion handles different tire radii (probably where your rust kicked in), another portion that handles e-stop tire rotation skid (brakes on), traction control (no brakes, engine off idle, one tire spinning (gravel?? or ice) and one not spinning (say on concrete).

 

I was working in Dodge Power Train Engineering for the last couple of years in my career. Building side, but got to talk with some of the development guys and gals - some cool stuff.

 

From the Volvo manual:pg 339 - http://www.hhrvresource.com/sites/default/files/dfiles/VolvoOperatorsManual_2006_%20PV776-20973492.pdf

 

TRACTION CONTROL SYSTEM (TCS) (OPTIONAL) The Traction Control System (TCS) uses the same wheel sensors as the ABS to determine if one set of drive wheels is spinning faster than the other wheel set.

 

If the TCS determines that a wheel is spinning (with vehicle speed below 25 mph [40 km/h]), it operates the brake system to apply some brake force to stop the spinning wheel(s). This puts the drive power over to the stationary wheel(s). If vehicle speed is above 25 mph (40 km/h), a signal is sent to the engine ECU, which reduces the engine speed to be consistent with vehicle speed. This action helps reduce the amount of wheel spin and gives the operator greater vehicle control.

 

The TCS includes a switch to turn off the function. When the switch is in the OFF position, the TCS operates normally to increase traction if the drive wheels begin spinning. When the switch is pressed once, the TCS telltale in the instrument cluster blinks continuously, indicating that the TCS is in mud/ snow mode.

 

The mud/snow mode increases available traction on soft surfaces like snow, slush or mud by slightly increasing the allowable wheel spin. This prevents the wheels from getting bogged down. The TCS will resume normal operation when the TCS switch is pressed again and the TCS telltale goes out or when the ignition is turned off. 340 Brakes

 

DO NOT engage the differential locks while wheels are spinning. Serious damage to the differential will occur. See “Differential Locks” on page 374 for more information.

 

So even the algorithms can be modified by the operator.

 

 

Randy - just for shucks and grins - you ever figured to torque hitting the wheels after going through the trans and differential?

Edited by Bill B
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Randy - just for shucks and grins - you ever figured to torque hitting the wheels after going through the trans and differential?

No, I have not. The VMSpc does show 450 HP and 1600 foot pounds torque when I am at 100% load. Back at the ranch I have one of those funkey little G-Force meters that computes rear wheel HP, 0-60 times, and G-force forward, stopping and sideways.... from there we could compute torque. But, for it to be accurate I must enter the exact weight of the vehicle - not an estimate. I have not weighed the truck recently and of course fuel adds or subtracts weight. I just might have to do it sometime. It was very accurate when I used it on the faux Ferrari (rebodied and 3.4L turbo powered 88 Fiero Formula).

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  • 1 year later...

Driving from Oshkosh to StL last night our ABS warning light lit up and even after stopping and shutting down for a minute it relit.

Looked it up in the manual and it says it is okay but to check brakes. Brakes were working fine, pressure is good etc.

We want to crawl under and have a look at the sensors but before we do, does anybody have a picture of what we are after and where they are located?

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