J2534 FAQs

J2534 FAQs

What is J2534?

J2534 is an interface standard designed by SAE (Society of Automotive Engineers) and mandated by the US EPA (Environmental Protection Agency) for vehicle ECU reprogramming. Its purpose is to create an API (Application Programming Interface) which would be adopted by all vehicle manufacturers, allowing the Independent Aftermarket (IAM) the ability to reprogram ECU’s without the need for a special dealer-only tool.

What is J2534-1 and J2534-2?

There are two parts to SAE J2534 -> -1 and -2. SAE J2534-1 defines features for a device that performs ECU reprogramming of emission ECUs (and could also apply to non-emission ECUs).

SAE J2534-2 defines optional features for a device that performs ECU reprogramming on other non-emission ECUs as well. It also offers a way for an OEM to reprogram all ECUs on their vehicles “using J2534” by releasing and publishing necessary protocol information about non-emission ECUs.

What vehicles are affected?

The US EPA regulation mandates that automotive OEMs must comply with SAE J2534 pass-through reprogramming from model year 2004 and forward for their Powertrain ECU’s. If an OEM cannot comply with J2534 by model year 2004, they may request one year additional extension to become J2534 compliant. Additionally, the specification includes a provision that allows OEMs to use the J2534 reprogramming method on 1996 through 2003 model year vehicles as long as OEMs make all necessary additional hardware (i.e. vehicle connection cables for use with device and/or it’s auxiliary pin) available to the aftermarket. If an OEM cannot retroactively implement the J2534 pass-through reprogramming solution with or without special cables, they must make available to equipment and tool companies any information needed to develop aftermarket equivalents of their OEM-specific reprogramming hardware and software.

Can I reprogram all vehicle ECUs?

J2534 pass-thru reprogramming is only required for emissions based ECUs (eg. Powertrain, Engine, Transmission, Throttle Controller) and is mandatory on all vehicles from model year 2004 and forward. Additional support of reprogramming Chassis and Body ECUs will be dependent on each individual manufacturer’s reprogramming application software capabilities.

Can I reprogram any Powertrain ECU?

Only those Powertrain ECU’s which are emissions-related and are Flash reprogrammable may be reprogrammed. Plus, the OEM will have to be performing reprogramming in its dealership on the particular Powertrain ECU as well.

Does J2534 affect all OEMs?

Yes, all OEM’s that sell vehicles in North America and support ECU reprogramming in their dealerships for emissions-related systems must comply.

When does the legislation take effect?

All OEM’s must have their ECU calibrations available by June 2005.

Where do I get the reprogramming application software from?

Each OEM is required to make available their ECU Reprogramming Application software on their own service information web sites. If ECU Reprogramming is practiced in the dealership, then it is the responsibility of each OEM to maintain and update their own sites, and keep current applications available for download. Note that a fee set by the OEM may apply.

Where do I get the ECU reprogramming calibrations from?

Each OEM is required to make available their ECU reprogramming calibrations on their own service information web sites. If ECU reprogramming is practiced in the dealership, then it is the responsibility of each OEM to maintain and update their own sites, and keep current calibrations available for download. Note that a fee set by the OEM may apply.

Are the ECU reprogramming calibrations free downloads?

Each OEM typically charges a fee for use of their site and/or for the ECU calibration download. These fees vary from OEM to OEM. Does the ECU reprogramming event utilize my Scan Tool? A J2534 compliant device for ECU reprogramming is considered a vehicle interface. A device requires a Windows-based PC (on which the reprogramming application software operates), with a USB or Ethernet port, and an internet connection (for Internet access to obtain reprogramming application software and calibration files).

Will I still need my Scan Tool?

Yes, J2534 reprogramming application software typically does not incorporate diagnostic Scan Tool functions that must be utilized to perform post-reprogramming tasks (such as clear DTCs or re-learn procedures). This is dependent upon the make and model of vehicle.

How long does a J2534 ECU reprogramming event take?

The programming time varies among vehicles based on communication speed of the protocol used, calibration file size, total number of calibration files, the number of ECUs to reprogram, and Internet connection (latter is dependent on OEM). Newer vehicles with CAN protocol may be as fast as 2 minutes, while vehicles with CAN that have a lot of data to download will take well over an hour. Older vehicles without CAN can take anywhere from 15 to 60 minutes.

Is a high-speed internet connection required?

High-speed Internet connection is highly recommended. You will be required to download the calibration files directly from the OEM websites, so shorter downloads equate to quicker reprogram times. Prevalent with European car makes, in some cases the OEM will require a direct connection between the vehicle, the in-shop PC (running the reprogramming application software) and the OEM server. It’s this latter condition that requires the speedy high-speed connection. Consult OEM website guidance for minimum Internet connection specification requirements.

What is critical for successful ECU reprogramming?

There a 3 key points that need to be followed for successful reprogramming. The vehicle’s system voltage must remain constant (specified by OE) during the reprogramming. The vehicle’s electrical system needs to be functioning properly (e.g. battery state of charge and state of health, cable connections and alternator charge performance). Note: Battery Testers can be a key addition to ensure these systems are up to the task of reprogramming. Follow the manufacturer’s reprogramming instructions in a step-by-step manner!

What tools does Bosch Diagnostic offer to fill my J2534 reprogramming needs?

Mastertech VCI, Flasher Pro, and Flasher LT support aftermarket reprogramming functions offered by OEM reprogramming application software. The General Motors MDI can also be used in the aftermarket although its intended use is with GM TIS.

Which vehicles can be reprogrammed using Bosch J2534 tools?

Vehicles with ECUs that can be reprogrammed are defined by the automotive OEM. Consult the OEM application guide for vehicles and ECUs that can be reprogrammed using the J2534 function. A check of the OEM service information website is often a good place to start. In addition, www.nastf.org may also contain helpful application information.