Revealed: secrets of the Bolt EV service manual


The official General Motors 2017 Bolt EV service manual is now available in both paper and PDF thumb drive formats and a quick skim reveals some interesting trivia.

Access to service manuals is one advantage that the customers of GM and other established automakers have over Tesla buyers. Tesla only publishes its service documentation online and in the United States it is only available if required by local law. Currently, Tesla documentation is only available in the United States for residents of Massachusetts. A 24-hour subscription is $100 and the annual subscription fee is $3000.

The official 4,488 page Chevrolet Bolt EV service manual, published by GM, is distributed by Helm. The paper version is $300 and comes bound into four volumes. The USB thumb drive version is $200 but requires Microsoft Windows 7 or later and can only be read while the USB drive is installed unless it is “printed” to a file. The thumb drive contains a Windows app which must first be run to unlock the PDF. It also requires a PDF reader application to be installed such as the free reader from Adobe.

There are also some unofficial online repair information services that carry vehicle-specific information.

And now a sample of some random finds from inside the manual….

“Colorful” colors

The service manual uses violence-themed names for the Bolt EV’s color choices rather than the happier names used in the vehicle marketing brochures: “Son of a Gun Gray” (US Bolt EV marketing name: Nightfall Gray), “Switchblade Silver” (Silver Ice), “Blue Me Away” (Kinetic Blue),  “Burning Hot” (Orange Burst), “Glory Red” (Cajun Red), “Blue Persuasion” (Arctic Blue), Black Meets Kettle” (Mosaic Black). The color name “Summit White” is the only name in common.

Different marketing names are often used by GM for the same company-internal color codes. It’s not clear if the names in the service manual were ever used by GM when marketing other vehicles in previous years. GM’s parts supplier subsidiary, ACDelco, uses these names in its line of touch-up paints that correspond to the Bolt’s available colors.

Fresh air

Owners in hot and humid areas might be pleasantly surprised to learn that there is a secret “afterblow” mode that will continue to blow air through the vehicle ducts after it is turned off in order to dry out the air conditioning system. Otherwise, the moisture left in the ducts can allow the growth of bacteria and mold that can sometimes cause odors. This mode is not documented in the owner manual but it can be enabled by a dealer service technician.

Braking news

The regenerative (regen) braking system uses the motor as a generator to slow the car in order to recover energy back into the battery pack instead of dissipating it as heat from the friction brakes.

According the service manual, the system can recover “almost all the energy lost in typical braking operations by ensuring deceleration rates of up to 0.3g [30 percent of the accelerating force of earth’s gravity] are achieved using the electric motor alone.”

Although the Bolt EV’s “One-Pedal Driving” capability can often bring the car to a full stop and hold the car in place without use of the brake pedal, the service manual says “the brake pedal should still be used to hold the vehicle at a stop, even when it may not seem necessary.” One reason for doing that is because the Bolt does not illuminate the rear brake lights after bringing the car to a stop unless the brake pedal is pressed. Although the manual does not say so, having the brake lights on may while stopped may reduce accidents by providing additional redundant information to drivers approaching the car from behind.

A computer with wheels

The Bolt EV has 4 major internal computer networks although they are interconnected in some ways. They consist of a low-speed bus, a high-speed bus, a dedicated powertrain high-speed bus, and a dedicated battery pack management high-speed bus. There are also various point-to-point low speed data links between computer modules and specific sensors.

There are multiple computer modules within the car connected by these networks.

12V power

There is a DC to DC power converter under the hood which takes energy from the large battery pack in order to run the radio, lighting, computer modules, and other common components that run at 12 volts. The converter takes the place of the 12 volt generator on a conventional engine and can supply up to 130 amps of power (about 1,600 Watts) when needed.

A 12 volt battery, also under the hood, supplies enough power to initially turn on the Bolt EV’s computers, reconnect the large battery pack which is normally isolated when the car is turned off, and then start the DC to DC converter. The 12 volt battery also supplies power for lights and accessories for up to 10 minutes after the car is turned off or until the driver door is opened.

12V battery maintenance mode

Many drivers are familiar with having a “dead” 12V battery either due to accidentally leaving a light on after turning off a car or having the lead acid battery self-discharge after sitting unused for several weeks. In order to reduce the need for jump starts, the Bolt EV has a 12V battery charging maintenance strategy.

If the car is plugged in but not charging, it will wake up and check the status of the 12V battery every 6 hours. If the 12V battery is low the car will begin charging it for up to 2 to 3 hours.

If the car is not plugged but has been turned on within the last 30 days, it will wake up every 3 days to check the 12V battery and if the main battery is at least 40 percent full it will begin charging the 12V battery for 45 to 90 minutes.

High voltage battery pack

The Bolt’s 288 battery cells are collected into 96 groups of three cells each. The three cells are electrically connected in parallel in order to form the equivalent of a single cell with a larger energy capacity. Under normal conditions, the 96 cell groups are kept within 0.03 volts of each other and “cell balancing” circuitry is used to maintain this uniformity as the overall pack is charged and discharged. If a cell begins to prematurely go bad (due to a manufacturing flaw, etc.) it will cause its cell group’s voltage to drop lower than the other cell groups and this will be detected by the battery management system.

See also: New details emerge as a few Bolt EV packs continue to fail

The battery pack has 6 internal temperature sensors placed in various locations. Even when the car is turned off it can periodically wake up to take its own temperature and cool its battery pack if necessary. The exact conditions under which it does this are not documented.

Coolant Loops

There are three independent liquid “coolant” loops which use the same basic water and glycol mix used to cool gasoline engines. One is used for the battery pack. Another is used collectively by the motor, the motor’s power inverter, the built-in battery charger used for 120 and 240 Volt AC charging, and the DC to DC voltage converter. Those loops each have their own radiator in the front of the car but share an electric radiator fan. The third loop is used for cabin heating. Its “radiator” is inside the cabin air duct and is used to exchange heat from the hot “coolant” into the fan-driven air. The cabin “coolant” is heated by an electric heater under the hood.

Cooling the battery pack is done by running a pump to circulate liquid coolant. A radiator fan can help bring down the temperature of the coolant and, if needed, the battery coolant can be chilled via a connection to the car’s air conditioning system. Heating the battery pack is done with a dedicated electric heater which is located outside but adjacent to the battery pack.

Fun factoids

Europe and Japan prohibit the use of the radar-based rear cross-traffic alert feature near special Radio Astronomy zones. The Bolt EV will use its GPS system to determine if it is entering those areas and then indicate a “Side Detection System Unavailable” message to the driver.

The heated steering wheel option keeps the temperature to 32C or 89.6F when enabled.

You cannot use cruise control while driving in reverse.

Did you know that headlights are adjusted differently in the United States versus South Korea and Europe? The details are explained starting on page 4-255.

Categories: General


19 replies

  1. Is there DRM on the flash drive that prevents one from copying it (such as to make a backup copy in case your original flash drive is lost or damaged)?


    • There is some kind of DRM scheme. The PDF file is scrambled or encrypted. You must install and run a Windows application which somehow descrambles the PDF which then allows you to use a normal PDF reader.

      I tried copying the files from the USB drive to the normal computer drive and then running the Windows app without the USB drive installed but that did not work because the Windows app complained that the USB drive was not installed.

      I have not yet tried “duplicating” the USB drive to see if that works.


      • If I had one and wanted to experiment the first thing I’d try was to make an ISO image of the entire USB drive then try to restore that image to a different flash drive and see if that worked. – to make the ISO – To burn the ISO to a different flash drive.

        In reality this would be one of the first things I’d do because I would always want to have a backup of something so expensive.

        Liked by 1 person

  2. Hacked bootlegs will be available on Ebay in 3…. 2….. 1….. 🙂


  3. Keeping the 12v up and ready is good. They should come up with a lithium starter battery like the Hyundai IONIQ Blue has. I also got one for my Tesla S 85 from

    Non toxic, 3 year warranty half the weight.


    • Not sure why you would be concerned with the toxicity. Are you planning on tasting the battery? Lead/acid batteries have a very high recycle rate.

      As an engineer, I simply find the whole concept of having a separate 12v battery to be kludgy. All that is needed is. 350v->12v DC/DC converter. If you drain the high voltage battery, well then you’re a twit and you’ll have to plug it in to recharge, tough.


      • But then the propulsion battery would be continuously connected. Having a second, less deadly, battery allows the high voltage battery to be totally isolated when not in use. There’s a trade-off, but it seems like a reasonable one to me. Maybe the DC-DC converter could be on the battery side of the switch that isolates the HV battery and continually connected? Not sure if that would cause more parasitic losses and you’d need a bigger converter (the battery can put out a lot more than 1600W). i suspect that at least a small secondary ballery is a good idea. Maybe not a full-sized car battery though.


      • The only car I personally know of without a 12V battery was the original Tesla Roadster. Tesla reverted to using a 12V battery in the Model S and subsequent cars. It seems like you could skip having a 12V battery but apparently it makes things easier to have one. I don’t know all of the reasons why they reverted.


  4. -Offtopic-
    So “innovative” documentation policy of Tesla innovative corporation.

    BTW, GM are the best.


  5. Interesting article, thanks.

    I wonder if they considered using a heat pump for heat and AC. More efficient.

    Unrelated question: is there a recall which would require hundreds of miles of driving in order to reset something? Picked up my new 2018 bolt with 700 miles on it, and the excuse that a fix for some recall necessitated it. Things that make you go hmmm


    • Yes, I’m sure they considered a heat pump but I don’t know all of the trade offs — good idea for an article.

      There was a “recall” that involved a software update to the computer that monitors and makes decisions about managing the battery pack. After the update is installed it takes some driving and a recharge or two for the computer to relearn some battery parameters and begin accurately estimating available driving range again.

      Does it take 700 miles to do that? I don’t think so. You are right to be skeptical.


      • Thanks for the quick reply. They did say that they had to charge it a few times. So maybe they were just being thorough.

        I enjoy your articles. Keep writing!

        Liked by 1 person

  6. would this service manual be accurate for a 2018 chevy bolt?


  7. Great info. Thank you. My new 2018 Bolt is using more than 2 kWh daily while sitting under a carport plugged in to level 1 charging with daily high temperatures in the low 90’s. I assume this is for battery cooling. I also have a full cover on it that blocks the front grill. Am I cutting off any needed airflow from cooling fans through the front grill?

    Liked by 1 person

    • You might be reducing the efficiency of any battery cooling but I doubt that you are harming anything.

      The liquid coolant (same basic stuff used for cooling gasoline engines) is run through a dedicated radiator and there is an electric fan that can blow air against it. Even if you have the cover partially blocking air flow through the front grill, the fan will be blowing air from under the car through the radiator. If the radiator and electric fan aren’t removing enough heat it will cycle on the air conditioner system to help remove heat from the battery coolant.

      So, I think the worst case is that the car might end up using the air conditioning system to help out more often than it would if the cover wasn’t partially blocking airflow through the battery coolant radiator.


  8. I wouldn’t do it. Even the A/C has to get rid of the excess heat, most likely through the same radiator you’re blocking!


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