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Things that may not be obvious about the EPB in maroon - scottf200 via the manual

The vehicle has an Electric Parking Brake (EPB). The P switch is on the center stack. The EPB can always be activated, even if the vehicle is off. To prevent draining the 12‐volt battery, avoid repeated cycles of the EPB system when the vehicle is off.

In case of insufficient electrical power, the EPB cannot be applied or released.

Before leaving the vehicle, check the Electric Parking Brake Light to ensure the parking brake is applied.

EPB Apply
The EPB can be applied anytime the vehicle is stopped. The EPB is applied by momentarily lifting up on the P switch. Once fully applied, the Electric Parking Brake Light will be on. While the brake is being applied, the Electric Parking Brake Light will flash until full apply is reached. If the light does not come on, or remains flashing, have the vehicle serviced. Do not drive the vehicle if the Electric Parking Brake Light is flashing. See your dealer.

If the EPB is applied while the vehicle is in motion, a chime will sound, and the DIC message RELEASE PARKING BRAKE will be displayed. The vehicle will decelerate as long as the switch is held in the up position.

Releasing the switch during the deceleration will release the parking brake. If the P switch is held in the up position until the vehicle comes to a stop, the EPB will remain applied.

If the Electric Parking Brake Light flashes continuously, the EPB is only partially applied or released, or there is a problem with the EPB. The DIC message SERVICE PARKING BRAKE will be displayed. If this light flashes continuously, release the EPB, and attempt to apply it again. If this light continues to flash, do not drive the vehicle. See your dealer.

If the Service Electric Parking Brake Light is on, the EPB has detected a system problem and is operating with reduced functionality.

To apply the EPB when this light is on, lift up on the P switch and hold it in the up position. Full application of the parking brake by the EPB system may take a longer period of time than normal when this light is on. Continue to hold the P switch until the Electric Parking Brake Light remains on. If the Service Electric Parking Brake Light is on, see your dealer. If the EPB fails to apply, the rear wheels should be blocked to prevent vehicle movement. For maximum EPB force when parking on a hill, pull the EPB switch twice.

EPB Release
To release the EPB, place the vehicle in ON/RUN, apply and hold the brake pedal, and push down momentarily on the P switch. If attempting to release the EPB without the brake pedal applied, a chime will sound, and the DIC message STEP ON BRAKE TO RELEASE PARK BRAKE will be displayed. The EPB is released when the Electric Parking Brake Light is off.

If the Service Electric Parking Brake Light is on, the EPB has detected a system problem, and is operating with reduced functionality. To release the EPB when this light is on, push down on the P switch and hold it in the down position. EPB release may take a longer period of time than normal when this light is on. Continue to hold the P switch until the Electric Parking Brake Light is off. If the light is on, see your dealer.

Notice: Driving with the parking brake on can overheat the brake system and cause premature wear or damage to brake system parts. Make sure that the parking brake is fully released and the Electric Parking Brake Light is off before driving.

Automatic EPB Release
The EPB will automatically release if the vehicle is running, placed into gear, and an attempt is made to drive away. Avoid rapid acceleration when the EPB is applied, to preserve parking brake lining life.
 

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TThe EPB can always be activated, even if the vehicle is off. To prevent draining the 12‐volt battery, avoid repeated cycles of the EPB system when the vehicle is off.
I believe this statement to be technically incorrect, especially as the manual then goes on to describe applying, releasing, and automatically releasing the EPB.

The EPB can *not* be activated to release the brake while the vehicle is off (I just tried it, to confirm my recall). I didn't try it just now, but it's my recall that it can be activated to apply the brake while the vehicle off.

Of slight annoyance, the EPB can't be released while the vehicle is booting either. The EPB *can* be released while in service mode, so that's a good way to wear down your AGM if you really want to.
 

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So it seems in an emergency you have to hold the EPB in the up position otherwise it will automatically release because the car is in gear. Hope I can remember this if I'm ever in an emergency. How do you modulate the amount of pressure? With an ordinary mechanical handbrake you can easily lock-up the rear tires, does the EPB not apply enough pressure to do this, or does it somehow know to not apply too much pressure? Perhaps the ABS tells it if the rear wheels are locked. Seems awful complicated for my poor old brain.

I love my Volt, but I think the EPB is overkill. I think the old mechanical handbrake is more reliable, and easier to use, particularly in an emergency. Just my 2 cents.
 

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Discussion Starter #4
The EPB can *not* be activated to release the brake while the vehicle is off (I just tried it, to confirm my recall). I didn't try it just now, but it's my recall that it can be activated to apply the brake while the vehicle off.
Confirmed as well when I went out for an errand tonight. You can engage EPB when the car is off but you can not disengage it (that I found). I could engage it twice ... meaning it seemed to "tighten" somewhat and then I hit it again and it "tightened" more. I supposed a kid could keep pressing it and it may try to continue to "tighten" using 12v power.
 

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Discussion Starter #5
So it seems in an emergency you have to hold the EPB in the up position otherwise it will automatically release
So in 30+ years of driving I've never used that brake for an emergency maneuverer ... only goofing around as teenager.

The EPB does work (stop car) when you are moving forward in gear. I did this at 10mph tonight on my errand. I'm I was going 60mph I suspect it would just "slow" me to a stop.
 

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If you EPB while your foot's on the accelerator, does it kill the motor? I've tried stomping the brakes with my foot on the accelerator, and that didn't kill the motor. I haven't tried standing on both, but I've heard that should kill the motor. Yes?
 

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Discussion Starter #7
If you EPB while your foot's on the accelerator, does it kill the motor? I've tried stomping the brakes with my foot on the accelerator, and that didn't kill the motor. I haven't tried standing on both, but I've heard that should kill the motor. Yes?
I was going at about 10mph when I applied the elect parking brake and it stopped the car but it kept running (started). Give it a try at a slow creep (ie. 5-10mph). Let's dispel the myths!
 

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I've used the emergency brake before for an actual emergency. The hydraulic brakes busted a rubber hose. Probably saved my life. It was the only way I could get the car stopped while going down highway.
 

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Discussion Starter #9 (Edited)

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Question: Do you always have to apply the EPB when you park the Volt? I only apply my parking brake on my 2009 Honda EX-L when I park on a hill or incline. Normally I park in relatively flat parking lots and my carport. None of which requires anything more than placing the transmission into "Park". Any difference when driving a Volt and parking it?
 

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Parking brake verses Hand Brake

I will be picking up my new Volt on Friday. Before I do I have a couple of questions. Most, if not all, cars have parking brakes that are either applied with a hand brake or a foot brake. In either case it is wire control to the rear wheels. It looks like this is not the case with the Volt. The reason for the non-hydraulic or electric parking brake is in the case of a complete brake failure you always had the hand/foot parking brake to help you stop. I downloaded the user’s manual and apparently this is not available as it’s applied via an electric switch. This does bother me a bit.
 

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Discussion Starter #13 (Edited)
Interesting point. Same could be said about the normal electric brake or electric steering (all these things being 'drive by wire'). I know I can brake or steer my other cars if I break a belt or main pulley (on end of camshaft) ... and have.

From the manual there is a separate fuse for it (F13) and there is specific lub recommended for the brake cable.

Make sure you check this thread out on the related discussion: http://gm-volt.com/forum/showthread.php?7854-Electric-Parking-Brake-a)-12v-b)-use-while-moving-c)-auto-unlock
 

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Discussion Starter #14 (Edited)
Question: Do you always have to apply the EPB when you park the Volt?
No. I normally do not use it.

Similar to any vehicle you can use it only on incline but you can use it even on flat surface as a 'backup' to forgetting to put your vehicle in (P)ark. (this is stated in the manual - not sure if it is in my other vehicle manuals and I'd be surprised if it was not.) This is a fairly common recommendation and probably have saved a few dented garage doors or whatever is in front of your car in the garage.

From the manual related to de/inclines: Section title: Park Brake and P (Park)Mechanism Check

Park on a fairly steep hill, with the vehicle facing downhill. Keeping your foot on the regular brake, set the electric parking brake.

. To check the electric parking brake's holding ability: With the propulsion system active and the electric drive unit in N (Neutral), slowly remove foot pressure from the regular brake pedal. Do this until the vehicle is held by the electric parking brake only.

. To check the P (Park) mechanism's holding ability: With the propulsion system active, shift to P (Park). Then release the electric parking brake followed by the regular brake.
 

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My sense of it has always been that, if the "service" brakes fail and you have to try to stop with the parking brake, the game is over anyway. When I've tried it the rate of deceleration has been negligible, LOL. Any modern brake system has a dual circuit master cylinder so that one set of brakes functions even if you lose hydraulic pressure to the others. So one broken hose does not totally disable the brakes.

On our race cars the parking brake systems are one of the first things we toss. Not enough utility to justify dragging the weight around IMHO. Of course we use steel braided brake hoses and keep totally on top of the maintenance, FWIW.

I'll say one thing for the Volt parking brakes. They hold. I have other GM vehicles with the foot actuted PBs and they really aren't that strong. You really have to be determined to drive away in a Volt with the PB actuated.

Anyway, based on my reading of Scott's link, you can actuate the "emergency' brakes while moving if you pull the switch out and hold it. This is a non-probelem, again IMHO.
 

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Thanks for the answer, Scottf200. That was what I thought, but after reading the earlier posts, it left the question in my mind. I am glad you cleared it up.
 

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I have had to use the emergency brake twice. Both times were Ford trucks, both saw very intermittent use, and what happened was that the brake piston became stuck in a position where it rubbed slightly and caused severe overheating, which cause hydraulic hose to rupture. One time I would have had a serious rear ender, the other time I discovered it before it was a serious problem.

The problem with the emergency brake (pedal type) was that I applied it bit by bit and nothing and then all of sudden wham... full on locked up braking, causing the truck to fish tail wildly, I kept it in my land but barely. And the person I nearly rear ended looked at me like I had lost my mind. Frankly, I was amazed I had remember to use it, she had no idea how close she had come to being in a serious accident.

My thought about the electric brake is this. I bet there is a sensor check the confirms the integrity of the circuit each time. The same can not be said for a mechanical/cable type. Which is only checked annually when you have your state inspection, if then.
 

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I will be picking up my new Volt on Friday. Before I do I have a couple of questions. Most, if not all, cars have parking brakes that are either applied with a hand brake or a foot brake. In either case it is wire control to the rear wheels. It looks like this is not the case with the Volt. The reason for the non-hydraulic or electric parking brake is in the case of a complete brake failure you always had the hand/foot parking brake to help you stop. I downloaded the user’s manual and apparently this is not available as it’s applied via an electric switch. This does bother me a bit.
FYI
While the electronic park brake IS electrically activated, it STILL uses a system of cables to mechanically operate the rear disc brakes. So the mechanical "emergency" brake feature is still intact up to ~5mph however at higher speeds it is initiated with hydraulic brake activiation until speeds drop to that point.So when indicated vehcile speed are greater than ~6mph and the park brake buttton is raised the ABS system will first apply hydraulic braking to about the 0.6g level, then once speeds drop to 5mph or lower it will commence to apply the motorized cable control.

The primary advantage is the motor actuator is ALWAYS able to adjust the brake to ideal tension based on real time feedback from motor resolver sensors and the ABS monitored wheel speeds. It therefore requires no routine adjustments, automatically releases if you pull away and forget to, and can be manually applied and modulated while moving by lifting UP on the button. The rate that the motor apples brake force will automatically be adjusted based on your speed- releasing the button (while still moving) immediately releases the tension.

Additionally the system can create warning messages to the driver if it's not working properly and store associated DTCs for diagnosis .
The Volt IS NOT the only car uing this as numerous other GMs (and competing OEMs) are using it as well.
It's a logical advancement/progression to the traditional park brake.
HTH
WopOnTour
 

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I note that other high-end cars also have electronic parking brakes. From Wikipedia...

New system: electric parking brake

A recent variation is the electric parking brake. First installed in the 2001 Renault Vel Satis, electric brakes have since appeared in a number of vehicles, including the Audi A4, A5, A6 and A8, the 2010 Subaru Legacy and Subaru Outback, the 2002 BMW 7 Series, Lincoln LS, Jaguar S-Type, XF and XJ, Renault Scénic, Espace , Laguna II.phase II , 2009 Opel/Vauxhall Insignia, 2010 Opel/Vauxhall Astra, 2011 Opel/Vauxhall Meriva, Volkswagen Passat, Citroen C6, the new Citroen C5, and the new 2011 Buick Regal.

Two variations are available: In the more-traditional "cable-pulling" type, an electric motor simply pulls the emergency brake cable rather than a mechanical handle in the cabin. A more complex unit uses two computer-controlled motors attached to the rear brake calipers to activate it.

It is expected that these systems will incorporate other features in the future. BMW, Renault and VW already have a system where the emergency brake initiates when the car stops and then goes off as soon as the gas pedal is pressed preventing the car from rolling. The vehicle operator can easily turn off the system.


Chris
 
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