On July 25, 2022, the U.S. Environmental Protection Agency (EPA) issued guidance letter CD-2022-12 (LDT, LDV) that revises the agency’s testing policy for how chassis-certified battery electric vehicle (BEV) manufacturers must determine the “default drive mode” used for official miles-per-gallon equivalent (MPGe) and range certification testing of vehicles that have multiple driver-selected mode options. However, determining the correct drive mode for certification testing may be difficult, and manufacturers must be mindful of how a driver may operate a vehicle outside of the mode selected for certification testing or risk an EPA defeat device enforcement action.

Unlike with other consumer products, the sales of motor vehicles require approval — or certification — of each model year from EPA, a process that applies to BEVs. With the continued market penetration of BEVs, EPA has been building out its regulatory interpretations and, with the subject guidance, is clarifying its regulations governing BEV MGPe and range certification. These regulations require vehicles to be operated per the manufacturer’s instructions provided that the instructions are representative of real-world performance.1

This requirement is fairly straightforward when the vehicle has one default, factory-set drive mode that engages every time the engine is turned on. However, as BEVs become more sophisticated and manufacturers offer enhanced customizable options for user-controlled drive modes (such as “eco,” “range,” “sport,” “tow/haul,” or “track” selections), determining the default mode for testing becomes more difficult. 

In determining this representative drive mode, EPA will look to whether multiple drive modes can “latch,” meaning that the mode, when set, is saved and re-engaged when the vehicle is restarted. If a vehicle defaults to the factory drive mode each time the key is turned on, then there is only a single, default drive mode. However, if multiple modes latch, the guidance requires that manufacturers either 1) test a vehicle in its best and worst latching modes (from an MPGe and range perspective) and average the results or 2) only test in the worst-case latching mode. This guidance supersedes for BEV only previous select-shift and multimode transmission guidance provided in EPA guidance letters CISDE-09-19, CCD-02-10, CCD-01-025R, and CD-87-01 and is applicable to testing for model year 2024 and later vehicles and may also apply to testing for model year 2023 if the vehicle requires new MPGe/range testing.

Key Points to Consider

While determining the proper drive mode to use for certification testing must be made on a case-by-case basis given the particulars of a given vehicle, EPA has provided the following instructive points applicable to many standard user-enabled options:

  • Generally, EPA will consider the factory drive mode that the vehicle is in when first delivered to be the default drive mode for certification testing barring “substantial evidence” that the vehicle will be driven in another mode. Such evidence may come from the owner’s manual or any publication from the manufacturer or the manufacturer’s proxy instructing the operator to use a different mode.
  • For vehicles with multiple key fobs, if each key fob can be programmed to start in a preset drive mode for each user, the vehicle has multiple latching drive modes.
  • If a vehicle has a manual drive selector (i.e., a shift lever or shifter) that can activate multiple drive modes, the vehicle will be considered to have a single drive mode only if the manufacturer provides the end user instructions on which mode to use for normal, everyday driving.
  • EPA will not consider modes that re-engage a user-selected mode across key cycles to be an additional latching mode in limited circumstances. These “soft latching” modes include those that are enabled by detection of a trailer or a timer set for less than 240 minutes (which would allow for a short stop for recharging but would default to the factory drive mode when parked overnight). Other methods of soft latching should be discussed with EPA prior to certification.
  • Drive modes not considered practical for street driving, including autonomous drive modes that limit vehicle speed and acceleration, do not need to be considered testable driving modes even if they latch.
  • Generally, anything that affects the transmission shift map (i.e., transmission shift points at a constant pedal position) or other characteristics that affect MGPe and range are drive-mode-effecting features that must be considered.
  • Neither primary vehicle controls — such accelerator, brakes, and steering — nor those unrelated to driving — such as headlamp switches, air conditioning, and audio controls — are drive-mode-effecting features.
  • Tire pressure, even if manually set, is a drive-mode-effecting feature.
  • Pursuant to an EPA waiver of preemption, the California Air Resources Board (CARB) has an independent certification process for BEVs, which other states may opt into, provided certain requirements are met. CARB frequently follows EPA guidance but does not necessarily adhere to EPA’s interpretations in all circumstances.

In issuing this guidance, EPA has made clear that manufacturers providing customers with the option to select multiple drive modes may be subject to enforcement action if the mode or modes used for certification testing are not representative of typical on-road driving. While BEVs may not have any emissions per se, EPA’s prohibition against defeat devices — an auxiliary emission control device that reduces the effectiveness of the emission control system under conditions that may reasonably be expected to be encountered in normal vehicle operation and use — always applies to BEVs just as it applies to vehicles with internal combustion engines. Therefore, manufacturers must take particular care to understand how it both allows and instructs users to change drive modes and work with their certification representatives to resolve any ambiguity before certification testing is conducted.