Most electric vehicles (EVs) utilize the OBD2 connector and ISO 15765 protocol for communication, similar to internal combustion engine (ICE) vehicles. This allows for diagnostics using standard OBD2 code readers. However, there are key differences and challenges when using OBD2 on an EV.
Many EVs based on existing ICE platforms, like the VW e-Golf, adhere to conventional OBD2 standards. These vehicles may also have brand-specific codes related to the electric powertrain, requiring proprietary diagnostic systems for decoding. Data from components like the DC/AC converter, DC/DC converter, electric motor controller, and battery management system is monitored, stored, and processed on individual ECUs.
A limitation of using standard OBD2 readers on EVs is that many pre-programmed codes, such as those related to fueling (P01XX), are irrelevant. Conversely, crucial EV parameters like State of Charge (SoC), cell temperature, and heating/cooling status, were not considered in the original OBD2 standard. This can limit the diagnostic information available through generic OBD2 scanners.
Some manufacturers, like Tesla, use proprietary diagnostic systems rather than adhering to the standard OBD2 protocol. However, adapters exist for some Tesla models, such as the Model 3, to enable connection with OBD2 devices. In the EU, legislation mandates EOBD (European On-Board Diagnostics), largely similar to OBD2, for M1 category passenger vehicles. Gasoline cars registered after January 1, 2001, and diesel cars registered after January 1, 2004, must comply for EU homologation. The applicability of this legislation to EVs at the time of its enactment requires further investigation.
Beyond onboard diagnostics, EVs exchange critical data with charging stations for safe and efficient charging. This communication involves parameters like SoC and battery temperature. The Open Charge Alliance provides valuable resources and information regarding EV charging communication protocols.
In conclusion, while OBD2 is widely used in EVs, its application presents both compatibility and limitations. Factors such as the vehicle’s make and model, specific diagnostic codes, and the need for specialized parameters necessitate careful consideration when performing diagnostics on electric cars. The evolving nature of EV technology and related standards will continue to shape the future of EV diagnostics.
