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As you all discover, the PM doesn't want to coast. Often I'll crest the mountain at a slower speed and then coast, hitting a faster speed at the bottom (say 50 onto 70 MPH and yes, I pay heed to overbraking and yes, I coast in D by letting off the gas).

PM don't play dat. But going down the mountain off throttle for some distance seems to precipitate a brake failure warning. Scares the **** out of me being told you've lost your brakes. Alas, the brakes are fine, or seem quite so. The warning persists until the next restart. Still scares me even though I've been through it before and the brake are fine.

I'm guessing that the "brain" assumes that if there is no effective braking while auto-downshifted for a number of miles, there just may be brake failure. Kinda like I suppose when it seems the outside temp is dropping and gets below 40F an icy road warning pops up even when things are bone dry. But I figured I would tap the collective knowledge. Anybody else getting this? Feature? Bug? Whatsup?
 

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But going down the mountain off throttle for some distance seems to precipitate a brake failure warning. Scares the **** out of me being told you've lost your brakes.

We have not experienced this. Ours behaves as expected (except maybe for the controversial downshifting) as we head downhill. One point of difference, we don't generally 'coast' downhill, rather, we have the cruise control set. It seems as if we're 'coasting' . . . but?
 

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There are a few of my hometown area roads that evolved from Bison trails turned to farmer market trails turned to paved roads, like Europes tiny country lanes not any modern surveyed right-of-ways; to press that PMs accelerator pedal down a even little bit coasting down through swoops and turns produces nearly the same butterflies in the pit of my stomach as does using the front brake on a motorcycle in snow or mud - it's something simply not done. Gives me the willies every time, especially with the drivers view out that huge windshield w/ no hood showing guardrails, fence posts, trees and rock banks going by 'within arms length' almost...

And a downshift like that in a rear-wheel drive car/pickup/van is recipe for rear wheels breaking loose in rain, snow or gravel - so it is yet another muscle memory that sings out EVERYTIME it happens... (remember that downshift w/ 4.10 limited slip differential and the skid/slide that inevitably followed where you missed wiping out seven different immobile objects... or didn't miss them?)

It gets easier living with the high-rpm downshifts if one imagines three or five Italian ambulance-chasing lawyers riding in the back waiting to sue Fiat when the vehicle surges five, seven or nine KPH and is 'obviously out-of-control' due to a design flaw as there were pre-engineered safeguards available but unused... </sarcasm off>
 

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As you all discover, the PM doesn't want to coast. Often I'll crest the mountain at a slower speed and then coast, hitting a faster speed at the bottom (say 50 onto 70 MPH and yes, I pay heed to overbraking and yes, I coast in D by letting off the gas).

PM don't play dat. But going down the mountain off throttle for some distance seems to precipitate a brake failure warning. Scares the **** out of me being told you've lost your brakes. Alas, the brakes are fine, or seem quite so. The warning persists until the next restart. Still scares me even though I've been through it before and the brake are fine.

I'm guessing that the "brain" assumes that if there is no effective braking while auto-downshifted for a number of miles, there just may be brake failure. Kinda like I suppose when it seems the outside temp is dropping and gets below 40F an icy road warning pops up even when things are bone dry. But I figured I would tap the collective knowledge. Anybody else getting this? Feature? Bug? Whatsup?

I've had something similar -- a code indicating a failure of the brake switch, which sets when descending long grades and using the engine as a brake. Dealer has replaced brake switch and other things associated with it, to no avail. Like yours, mine resets on it's own.
 

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Another "works for me" here: I've rolled down several large slopes (I70 into Denver, I17 into Phoenix among others), and have never had any warnings. I follow the rule of "maintain speed with the throttle, reduce speed with the brake" - pick a gear that allows the engine to maintain speed with just a hint of throttle input, and if you need to slow down use the brake. If you start to pick up speed with no throttle input, brake to a lower speed and downshift. Maybe the presence of just a bit of throttle is enough that the computer is satisfied the vehicle is under control.
 

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Does this has something to do with the brake fluid level indicator being on the drivers side of the reservoir. When you go down hill, it thinks it is low on fluid and then is fine once you level off.
 

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What does the warning say, exactly? I believe there is a specific warning for low brake fluid. Brake fluid level due to the slope would be my guess though, unless you are driving 2 footed or have a brake caliper dragging. It doesn't make sense that the system would otherwise trip without the brakes being applied, as brake application is a very logical yes/no input. Have you checked the master cylinder reservoir level?

FWIW, I have the diesel and have driven down most major highway grades in the US using engine braking without seeing this one.
 

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I had this happen three times on a Sept 2017 trip. The message that appears on the dash disappears quickly - SERVICE BRAKE or BRAKES (not sure which) and a third word I think, but it disappeared so quickly I missed it each time. The red brake light on the dash comes on and stays on until engine is shut off. The same warning light fore having manual parking brake on. I expect a recall to fix this false warning.
 

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I get that (service brake system light) almost every time descending Eisenhower Tunnel to Silverthorne on I-70 somewhat aggressively. If I keep it under 70 MPH and take the curves somewhat smoothly, then I can avoid the light. However, Vail pass is fine; as are all the east bound descents on I-70.
 

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Discussion Starter #10
Maybe the presence of just a bit of throttle is enough that the computer is satisfied the vehicle is under control.
That's what I'm thinking, that the programmer didn't consider a 8 mile descent on a slope that allows only engine braking to control speed.

Hmmm, I guess make that a 12km descent, lol. It does seem like the warning comes on consistently at 10km.
 

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Discussion Starter #11
What does the warning say, exactly? I believe there is a specific warning for low brake fluid.
Good point being made here on low brake fluid. It seems to take several miles of no brake coasting before the light comes on. In fact, this is not on the steepest slope where this happens as the slope grade has to be one that coasting doesn't build up too much speed not to touch the brakes for like 5 miles.

I don't recall the exact message but it has nothing about fluid level. More like "Warning: Brake System Failure". Attention getting, isn't it.
 

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I guess I don't really count letting off the accelerator as coasting because the vehicle is still in gear. Engine braking perhaps.

The reason I love to slip the vehicle into neutral (or push in the clutch on my car) is for the fuel economy. In particular, when tooling down a quiet highway with a stop sign ahead in the distance, you can slip into neutral and coast perhaps a half mile to the stop sign, with mpg pegged at 99.9 the whole way. I just slip the unit back into gear at the last (<20mph) for a smooth stop. This seems to work with the diesel. When we head up to Chicago to visit my older son, there's a spot where McNabb Road goes over I-39 where we coast the better part of a mile to the stop sign.

Am I really saving the world or even any money by doing it? Probably not, but it makes us laugh and break out with a rousing refrain of Edgar Winter's "Free Ride"!
 

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Does this has something to do with the brake fluid level indicator being on the drivers side of the reservoir. When you go down hill, it thinks it is low on fluid and then is fine once you level off.
This theory was verified by a mechanic. The sensor is towards the back of a very small, flat reservoir. When the vehicle is tilted forward enough, there will not be fluid on the sensor, setting off the warning. As your brakes wear, and more fluid is displaced (or, if you are low on fluid) you are more likely to see this warning. But I do think the warning was "low brake fluid" (or something similar), there may be more than one brake warning..
 

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As you all discover, the PM doesn't want to coast. Often I'll crest the mountain at a slower speed and then coast, hitting a faster speed at the bottom (say 50 onto 70 MPH and yes, I pay heed to overbraking and yes, I coast in D by letting off the gas).

PM don't play dat. But going down the mountain off throttle for some distance seems to precipitate a brake failure warning. Scares the **** out of me being told you've lost your brakes. Alas, the brakes are fine, or seem quite so. The warning persists until the next restart. Still scares me even though I've been through it before and the brake are fine.

I'm guessing that the "brain" assumes that if there is no effective braking while auto-downshifted for a number of miles, there just may be brake failure. Kinda like I suppose when it seems the outside temp is dropping and gets below 40F an icy road warning pops up even when things are bone dry. But I figured I would tap the collective knowledge. Anybody else getting this? Feature? Bug? Whatsup?
I had the same brake warning experience when driving to AK this summer on a long downhill. The brake warning went away after restarting and I continued driving to the next town with a dealership. They ran a basic diagnostic and told me it was fine to drive. I continued on to Anchorage and brought it to a dealer there. When I told the service guy I had a brake warning light come on he described the exact conditions under which it happened, long downhill engine braking, and said they had seen a bunch of those and not to worry about it.
 

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AND NOW HE’S ROLLIN’ DOWN THE MOUNTAIN
GOING FAST, FAST, FAST
AND IF HE BLOWS IT THIS ONE’S GONNA BE HIS LAST
RUN TO ACAPUCO TO TURN THE GOLDEN KEYS
HENRY KEEP THE BRAKES ON FOR THIS CORNER IF YOU PLEASE
by New Riders of the Purple Sage
 

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AND NOW HE’S ROLLIN’ DOWN THE MOUNTAIN
GOING FAST, FAST, FAST
AND IF HE BLOWS IT THIS ONE’S GONNA BE HIS LAST
RUN TO ACAPUCO TO TURN THE GOLDEN KEYS
HENRY KEEP THE BRAKES ON FOR THIS CORNER IF YOU PLEASE
by New Riders of the Purple Sage
New Riders :DGot to see them many times in my youth!
 

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I can confirm that this is not a 'rare' occurrence. Has happened to me 4-5 times as I come down off a pass in the Rockies. It always resets after I turn the engine off and restart. This is a 2106 PM with less than 15,000 miles.
 

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the promaster does have this annoying feature -- the computer kicks in when it sees instant mpg is 99 and no gas input is used-- the tansmission kicks down a gear to use the engine as a brake thinking we need to slow down --- **** you engineers -- im trying to save money on fuel costs.. the only thing i can say is approach the top of the hills when you can as slow as you dare then just try to a tad touch of gas pedal going down -- more dangerous then coasting but then it prevent engine braking.... sigh .
 

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Brake warning message and light came on for the first time on a steep downhill in Colorado. Brakes seemed to work fine but used more engine braking than normal just in case.


When we reached the bottom of the hill in Pagosa Springs we stopped, shut off the van for several minutes and then restarted it. No warning and light was off and has been off for several days.



Brake reservoir level is midway between min and max. Brake pads were listed as ok at 30k service in March.
 
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