This article was adapted for drivers and tuning professionals in the United States by Viezu USA. Measurements are shown in US units alongside the originals.
One Bench Patch, Then OBD Tuning on GPEC2A
Free unlock. Same-day tuning.
ECU tuning never stands still, and Alientech has delivered another meaningful technical step for professional tuners. A recent KESS3 update lets you unlock and patch GPEC2A ECUs on the bench, permanently enabling safe, repeatable OBD tuning.
That's a big deal for shops working on high-performance and late-model Stellantis vehicles, including Jeep, Dodge and Chrysler platforms.
Technically, the update doesn't just "add coverage." It fundamentally changes how the GPEC2A is accessed: an ECU that used to be bench-only can be serviced efficiently through the OBD port after a one-time preparation, streamlining your workflow and improving profitability.
Why GPEC2A Has Been Hard to Tune
The GPEC2A engine control unit, used widely across Dodge, Jeep and Chrysler vehicles (including the Dodge Challenger 6.2 SRT Hellcat), has historically been tough to get into because of advanced manufacturer security. Protected boot sequences and memory access restrictions block standard OBD reads and writes.
Until now, tuners had to use bench or boot-mode access for every tuning job, even minor revisions. For a shop, that meant more labor time, more handling risk and less chance of same-day tuning.
The KESS3 GPEC2A Patch
The latest KESS3 protocol tackles those limits by changing the ECU's access permissions in a controlled, manufacturer-aware way. A one-time patch, applied on the bench, modifies the internal security state so the ECU accepts OBD communication afterward.
From a technical angle, the patch offers several safety assurances:
- Structure preserved: the original ECU software structure stays intact.
- Data protected: calibration data isn't overwritten.
- Access enabled: the boot/communication logic is altered to allow OBD write access.
After that, no more repeated bench sessions. It's ideal for high-performance vehicles that need revisions: one controlled unlock, then safe, repeatable OBD tuning.
Bench setup and tool tips
In the video, Simon White shares expert wiring tips:
- Use a labeled bench mode cable for GPEC2A
- Apply the correct BOOT-line resistance (KESS3)
- Work on a non-slip bench or use a clamp for secure contact
- Always back up the ECU before patching
Want more confidence on the bench? A Viezu tuning course gives you in-depth, hands-on training.
Step by Step: Unlocking GPEC2A With KESS3
This is strictly professional work, for trained technicians with the right equipment only. It means opening the ECU and making direct connections before the software patch goes on.
1. Prep and open the ECU
The aim is controlled access to the PCB without flexing or stressing the board. Too much leverage or any contamination can permanently damage sensitive components.
- Bend the tabs: carefully bend back the metal tabs around the unit just far enough to clear the main ECU board.
- Separate the lid: slide a flat edge or screwdriver between the lid and the main frame. Critically, lever away from the circuit board, going in no more than 4–5 mm (about 3/16 in).
- Clean the contact: use a fiberglass pen to gently remove the protective seal from the specific resistor/connection point (CNF1). Note: this step really matters, because poor contact here can interrupt the boot sequence during the critical patching phase.
2. Make the bench connections
With the ECU open, you need a connection that lets KESS3 take control of the ECU as it starts up.
- Raise the ECU: put a support (such as a roll of shop tape) between the two connector plugs so the ECU sits flat without crushing the wires.
- Bench cable: connect to the gray connector plug for power and communication, following the manual.
- Boot pin (CNF1): a BDM frame with pogo pins is strongly recommended for repeatable, non-invasive contact without soldering. Make sure the probe sits firmly on the copper pad/resistor you cleaned.
3. Apply the patch
The process is designed to be safe and recoverable.
- Identify: connect KESS3 and press "Identify."
- Back up: choose the "ECU Patch" function. The software first makes a complete backup of the ECU's internal memory (Micro and EEPROM), preserving the original software state so full recovery is possible if needed.
- Patch: with the backup saved, the software patches the backup file and writes it back to the ECU, updating access permissions while keeping the factory calibration logic.
- Finish: a new backup file with a .PT extension is created. The ECU is now OBD-enabled.
4. Seal it up and switch to OBD
Once patched, the ECU can be resealed and treated like any other OBD-capable unit, with no boot pin or bench connection needed for future tuning.
- Remove the boot pin and bench connections.
- Run a thin bead of high-temperature automotive silicone around the lid to keep it watertight.
- Bend the tabs back and reinstall the ECU in the vehicle.
For the full walkthrough, including wiring tips and real shop footage, watch Simon White's complete YouTube tutorial.
Watch the video
Why now is a good time to buy KESS3
This unlock was designed specifically for Alientech KESS3, and it's the tool we recommend. Similar methods are also possible with:
Unsure whether your tool is compatible? Our support team can advise.
Who should move on this
- Tuning shops wanting to support more US vehicles
- Current KESS3 users who haven't added this ECU yet
- New tuners ready to invest in a tool with high-value protocols
It's a strong reason to upgrade now. With no license cost and wide vehicle coverage, KESS3 delivers immediate ROI for tuners working on Dodge, Jeep and RAM vehicles.
Become a Viezu dealer for tools, files and support.
Supported vehicles
The method covers most GPEC2A ECUs in FCA vehicles from 2015–2021.
Security note:
ECU-level security and vehicle network security are two different things.
- The KESS3 patch unlocks the ECU for OBD writing.
- Vehicles built after 2018 have a Secure Gateway Module (SGM). You'll still need an approved bypass method (such as an FCA 12+8 cable) so diagnostic communication can pass through the vehicle network to the now-unlocked ECU.
Tuning RAM, Dodge or Jeep and need help checking software versions? Our team can help.
Why Viezu?
KESS3 handles GPEC2A ECUs so well because its unlock process is manufacturer-specific and works with the ECU's architecture instead of forcing generic boot access, which greatly reduces the risk of corruption compared with improvised methods.
Viezu has supported thousands of tuning professionals for more than 15 years, with training resources, technical guidance and file support so updates like this can be put to work safely and profitably in real shops.
Need tools or tuning support?
Viezu has everything you need to start unlocking and tuning GPEC2A ECUs:
Unsure whether your tool is compatible? Our support team can advise.
GPEC2A Tuning FAQs
What makes KESS3 a leading tuning tool?
Alientech KESS3 combines OBD, bench and boot tuning in one device, and uses ECU-family-aware protocols and automatic backup handling for safety.
Is the GPEC2A patch a one-time job?
Yes. After it's applied, the ECU doesn't need repeated bench access, and every later calibration update can go through the OBD port.
What are the risks of opening the ECU?
Opening an ECU is risky if the board gets stressed or flexed. Overall, though, the KESS3 update lowers mechanical risk, because the ECU only has to be opened once instead of for every revision.
US emissions compliance note
In the United States, modifying, removing or disabling emissions-control equipment (including DPF*, EGR*, SCR*/DEF* and catalytic converter systems) on a vehicle used on public roads may violate the federal Clean Air Act and EPA rules, and in California and other states that follow CARB standards, additional restrictions apply. Any off-road, race or competition-only modification described here is not intended for street use. Nothing in this article claims that any product or calibration is EPA- or CARB-certified or street legal. For guidance on options for your vehicle, contact Viezu USA.
Talk to Viezu USA
Want to know what Viezu can do for your vehicle or your business? Request a performance upgrade quote, browse viezuusa.com or contact the Viezu USA team.
* EMISSIONS TAMPERING WARNING
Removing, disabling, deleting, or rendering inoperative any emissions control device or system (including DPF, EGR, SCR/DEF, catalytic converters, and related sensors or software) on a vehicle used on public roads is prohibited under the U.S. Clean Air Act and may also violate state laws, including California Air Resources Board (CARB) regulations. Violations can carry substantial civil penalties for vehicle owners, installers, and sellers.
Any reference in this article to DPF, EGR, SCR, or other emissions-related functions is provided for informational purposes and, where applicable, for closed-course competition or off-road use only where permitted by law. Viezu USA does not condone emissions tampering on any road-going vehicle. It is the customer's sole responsibility to ensure that any modification complies with all applicable federal, state, and local laws, regulations, and policies, regardless of what country you live in.