Mountain mode should only start when the charge gets down to a set point (for Gen1 I believe it's 40%?). Above that it will deplete the battery. Opening the hood when on runs the engine to make sure it doesn't start unexpectedly when your hands are in the engine bay, it's not really Mountain Mode.

12V battery could be failing. I would get it load tested and see. 2 years is fairly young but I've had young batteries fail before. I'd start there.

 

There are two separate problems here. First, the speed sensor issue. It's pretty obvious that the wheel speed sensor is either damaged the or the wire connecting the speed sensor. Go to the 2 minute mark of this video:

The speed sensor is supposed to be removed before you take off the CV joint, which is not common. Your typical mechanic wouldn't realize this because, on most cars, the speed sensor is integral with the wheel hub assembly. Fortunately, the speed sensors are pretty inexpensive.

 

The "no heat on electric" issue is the subject of many threads. Here are two: No heat when running on battery power, how I fixed it!
No Heat in Electric Mode - Heater Pump Replacement - DIY?

 

Sorry to hear you're having so many problems with your Volt. I had a bad wheel bearing on my Gen 1 Volt I replaced around 50,000 miles. After replacing I had issues that you are describing. Turns out when I reinstalled the axle nut I used an impact gun to tighten it. Big mistake, need to use a torque wrench like in the video. One of the tabs on the washer/spacer that rides on the inside near the CV joint broke off and stuck to the wheel speed sensor which is a magnet. This may be what happened at the shop. (By the way for anyone watching the video, you don't need to remove the lower ball joint or the upper control arm or strut to get the CV axle out. You can turn the steering wheel all the way to the stop and there is enough clearance to remove the axle) If the dash is still lighting up faults, they need to go back and check the sensor and the sensor ring for something metal stuck to it. They will also need to clear the fault codes.

Not sure why the tire shop recommends replacing all the wheels to fix the one that may be causing a leak. Unless the wheel is damaged, bent, cracked somehow, it shouldn't cause a leak. I had one the was leaking around the edge of the rim so they had to break it down, clean the bead and reseat it. It's been good since then.

Sounds like a problem with the electric heating element or the electronics that control it. Like Kato659 said, popping the hood isn't the same as mountail mode, but it does force the engine to run when the car is powered on. Maybe it would work to open the hood for a little while on those cold mornings and let the engine warm up with the heat on until the heater can be repaired? At least the cab would be warm for a while. Mountain mode won't work until you drain the battery down to a certain point as Kato659 mentioned

If your car is dead and comes to life when you touch the 12V battery connections. The connections need to be checked/tightened. That would cause a complete loss of power if they're not making good contact.

Once again, sorry for all the issues but sounds like the repair shops aren't helping the situation.

 

To add:
With the 12v, make sure it's the correct AGM battery which should be listed in the owners manual. Don't try and save money by using the wrong battery, as it can cause issues.

 

We have a whole FAQ on replacement batteries, process, etc.

Chevy Volt 2011-2015 12V Battery replacement FAQ

Quick Answers: What battery does the Gen 1 (2011-2015), need? AGM BCI Group 47, GENERAL MOTORS OE Part Number: 88864595 How do I replace the battery? See general info below. Pros and Cons of AGM Batteries? Pro: Longevity, Safety. Con: Cost Does the battery have vent/overflow hose connected to...

www.gm-volt.com

 

Also, I have NO heat. IF and only IF I can get it to switch to mountain mode, I get some heat. BUT, the car won't switch to mountain mode until the charge is depleted. I can push the drive mode button and it shows it switching, but it stays in EV mode. IF I pop the hood it does go to mountain mode though! I live in Indiana one day it's 75 and sunny and the next it's 25 and snowing. I NEED HEAT!!!

JMcA, Does your '12 have a "hold" mode? That is intended to maintain a battery charge level at whatever it is by using the gasoline powered generator. That can get you combustion sourced heat if the battery powered heat isn't working. My '14 gen1 Mountain Mode activates the gasoline engine only at 50% battery charge or less, but Hold in mine can be used to start the gasoline engine at any battery charge percent (other than fully charged or zero remaining).

 

I am not aware of it. If so I haven't figured it out. I know there was one time I somehow put it into the "service" mode on accident one time. 20 phone calls, lots of googling, LOTS of cuss words and tears, and 4 days later I learned about "service" mode. That was a freaking nightmare. The chevy dealers in my town and within a 20 mile radius of course wanted to "tow er in and have a look at er" for $850 to go across town.

I have not been charging every day. It's been warmer lately. So on the warmer nights I leave it unplugged, to where I can turn the heat on in the morning for the kids. So it's been manageable. Does not solve the problem by any means, but it's working for now.

 

I had the same issue with mine, every time a CV axle was replaced I got a bunch of codes and the dash lighted up like a Christmas tree. I had to replace either the wheel bearing or wheel speed sensor every time this happened.

Since I have done these types of repairs myself (DIY) previously and experienced these issues on other cars, it may be just a “that’s the way it is“ thing and plan to replace the other parts such as wheel bearing or speed sensor at the same time.

I hope it’s a simple fix, but having experienced the exact same issue on my 2012 I am guessing it’s one of the two common failure points above.

 

The wheels should be something a tire shop can refinish. I too live in the Midwest and have had some really badly rusted wheels where every shop told me I couldn’t use them anymore due to a leak. Found a good independent mechanic to seal the heck out of the bead with bead sealer after scraping the rim super clean for an hour. The key is, scrape the rim clean for however long it takes to get the rust out. My wheel now loses like 1psi a week…much better than the 10+ psi overnight…

 

Kind-of what I thought. It was Discount Tire. And it wasn't one of their tires. So they didn't want to fix it probably. BUT...since warmer weather I've not lost any air at all in ANY 4 tires! 😁

 

2012 Chevy Volt 166,760 miles
I have tried my best to try to figure things out on my own but I I'm just stuck.

So let's start here, acouple months ago started hearing a clicking noise coming from the driver side front tire that sounds like a roller coaster. Come to find out the CV axle is bad. Call AutoZone ordered the part had the part picked up same-day $109. Call around to local garages in my town of Kokomo, Indiana to get to a place called Dad's garage. They say no big deal we can get it done Bing Bang Boom. Almost a week later, I Drop the car off at 9 in the morning they were calling by 10 stating that my passenger CV axle is also bad and needed replaced. I asked them what that was going to cost me they wanted me to pay 165 for the part. And then 145x2 for labor! I said no thank you I'll order the part myself.

Now, ever since they replaced the cv axle...i drove a half a block and lost acceleration. The ABS, TRACTION CONTROL AND ENGINE LIGHT, all came on! I called, took it back, they admitted that it was the first Volt they ever touched, but all vehicles are standard 😒they jacked it up, cleared the codes, and even drove it. Came back and said it should be fine! Later that night exact same thing happened. So my dash is still lit like a Xmas tree! I found out it is the front left wheel speed sensor that is making these codes show up. But Dad's Garage says it all looks fine. But clearly something Is wrong.

Been having issues with psi in tires. So, I took it to Discount Tire, where the tires were from. They checked it out? Said the front tires were shot I needed new ones. Luckily I had two tires already. They are 215/60/R17. But they work. So they take the no-good ones off. The back get moved to the front and the new on the back. Wake up the next day with a psi of 18! Took it.back, come to find out, it's the rim! So they tell me that I need to order new wheels. But I'm trying to just find one for the messed up one.

Also, I have NO heat. IF and only IF I can get it to switch to mountain mode, I get some heat. BUT, the car won't switch to mountain mode until the charge is depleted. I can push the drive mode button and it shows it switching, but it stays in EV mode. IF I pop the hood it does go to mountain mode though! I live in Indiana one day it's 75 and sunny and the next it's 25 and snowing. I NEED HEAT!!! SIDE NOTE- I did change the blower motor a few months back. There is plenty of air flow. Just really really cold air!

Also! 3 times now, within 4 or so months, I get up, take my daughter to school, go back home (maybe.4 blocks) get my son ready, go to the car and it's COMPLETELY dead. No welcome sounds, lights, can't pop the trunk...nothing
So I get my jumper box, barely touch the 12v and the entire car starts! Then of course everything is reset. But it runs fine for a while. The 12v battery is around 2 years old. Is something drawing power from the 12v? What could possibly just randomly do that? .

I am just at my wits end with it all. Nobody near me knows anything about the Volts, so they say. Everyone says take it to dealer. Well j don't have dealer money to get it looked at!

Any help or advice is appreciated! Thank you!

3 VEHICLE MESSAGES

1. SERVICE AIRBAG (I believe sensor under passenger seat issue)
2.SERVICE STABILITRAK
3. SERVICE BRAKE ASSIST

ENGINE LIGHT ON
TRACTION CONTROL LIGHT ON
ABS LIGHT ON

There is a thin wire that connects to the ABS speed sensor, check that the wire is not cut or insulation is rubbed off. The wire has a clip to stop it from rubbing on the cv driveshaft. Check the cable I had the same problem solved it liquid Ruber and tie strap.

 

The dead battery situation has happened a few times since my posting. Is it possible something could be drawing the power? I don't know what it could be. Everything seems to shut off when the car does! I Am pretty confident that I hhave The correct battery. I did a lot of research before buying one. And I remember being.upset by how hard it was to find one.

Another new found issue.....the REMOTE start won't work. Whether from the key fab, or my app. It just flashes the yellow lights and that's it. Never starts up!

I need a miracle here!!!!

 

The dead battery situation has happened a few times since my posting. Is it possible something could be drawing the power? I don't know what it could be. Everything seems to shut off when the car does! I Am pretty confident that I hhave The correct battery. I did a lot of research before buying one. And I remember being.upset by how hard it was to find one.

Another new found issue.....the REMOTE start won't work. Whether from the key fab, or my app. It just flashes the yellow lights and that's it. Never starts up!

I need a miracle here!!!!

Remote start won’t work if the fuel gauge says LOW. It also won’t work if the check engine light is on. It also won’t work if it thinks one of the doors isn’t shut.

 

Have you checked the battery terminals as Peoria suggested? A loose or damaged one could cause the car to not power up.

In a regular car I would be looking for corroded or dirty terminals as well but an AGM wouldn't be gassing off to cause corrosion (and the battery lives in a generally clean spot). Could be worth double (triple?) checking to make sure the battery is in fact Absorbant Glass Mat if you decide to check the state of the terminals.

 

 

I had similar behavior on my 2012 when the 12V was dying - it had enough current to power up the computers and even crank the stereo, but not enough voltage for all the sensitive electronics to function properly.

Try a new 12V - worst case you’ll have to return it if it’s not the fix (most places I been to never had an issue with returning a 12V AGM battery the same day if it’s in the same condition)… no questions asked, I even was upfront about why I was purchasing and they let me do the return…