It wasn’t but two years ago that GM released the latest L5P Duramax platform for the 2017 model year. This engine wasn’t just getting the usual every-other-year updates with a little different EGR system and an ECM flash for more power/torque from the factory. The L5P was basically all new from the crank up. GM switched over from the Boschbased injection systems they’d been running since the Duramax was introduced back in 2001 to a Denso fuel system capable of higher injection pressures for more power and cleaner emissions. The oil-controlled Garrett variable-geometry turbo is gone, an all-new electronically controlled BorgWarner VTG in its place. The complete emissions system has been reworked with larger coolers, improved fl ow, and even a large catalytic converter clamped directly to the turbo outlet. GM engineers meant business when it came time to redevelop the Duramax powerplant for 2017, and with better emissions control, improved fuel efficiency, and enough horsepower and torque to virtually move a house, they weren’t going to cut any corners.

This became especially true when it came to the Engine Control Module (ECM), which turns out to be one of the most advanced in any OEM diesel vehicle to date. GM went to great lengths to develop computer hardware that would be untouchable to an outsider. Without a direct GM connection, gaining access to the ECM to make flash updates or changes was basically impossible. We’ve been told this was for safety reasons, since self-driving cars are now a thing, and we suspect GM doesn’t want to be held responsible if some random computer hacker breaks into your vehicle’s ECM via cloud or Wi-Fi and tells it to drive off a cliff. Up until just a few months ago we all thought that L5P computer was going to be uncrackable, that “performance tuning” or “chipping” your truck would soon be a thing of the past. That is, until we started hearing rumors this past August that a tuned L5P was soon to surface. The day came in mid-September, when HP Tuners released a little teaser video clip that quickly broke the diesel Internet for a day with more than 70,000 views in a matter of hours.

HP Tuners had quietly spent months on the L5P ECM, reverse engineering and making internal hard part and circuit board changes within the ECM to allow full flash access via their already popular VCM Suite 4 tuning software. Due to the extensive internal changes required within the ECM, at this time HP Tuners is requiring your vehicle’s ECM, or a spare ECM, be sent directly to them for modification. Once the modified ECM has been sent back, your preferred and trusted tuning company can tailor custom tuning to fit your needs, whether it be a mild jump in power for daily driving or for an all-out competition platform. There are a handful of performance tuning companies working tirelessly in tune development, with 150+ horsepower and 300+ lb-ft of torque already being achieved. is one company that has been working closely with HP Tuners in developing and expanding the required tuning tables to data-log and adjust engine calibrations as needed to fine-tune the L5P platform. The talented engineers at HP Tuners have really created something special here, but there are some things to consider before you jump on the “tuned L5P” wagon.


First, these ECMs work on a straight exchange process, meaning you send in your ECM and VIN number and HP Tuners returns a modified, ready-to-flash unit. While that sounds easy enough, tuning the truck still presents some hurdles, as you’ll need help from someone with ties to GM flashing software to “marry” it back to your vehicle to retain full functionality for the rest of the truck’s electronics and security system. Once modified, the HP Tuners ECM can no longer be tuned via the OBD-II port with anything other than HP Tuners hardware. This means no other tuning or calibration tools may be used, including a dealer re-flash. GM can no longer access the truck’s computer electronically. So unless you have a really great connection at your GM dealer, you can most likely kiss that factory warranty good-bye.

Now that we’ve scared you out of even thinking about tuning your L5P, let’s explore some of the high points to all of this. Nick Priegnitz, owner and lead calibration specialist at, tells us he’s extremely impressed with the L5P’s capabilities in stock form. Even with very little seat time tuning, dyno testing, or towing, the new custom tuning they’re working on shows promising results. There should be no reason an otherwise-stock truck won’t be reliable and safe around the 535 rear-wheel-horsepower range. They’ve pushed the truck to 570 hp, but the data and results they’re seeing with stock emissions equipment and turbocharging makes Priegnitz nervous of what that could cause without more time behind the wheel dialing in the tuning. For him, it’s one thing to make as much power as possible in a new platform, and a whole other thing to make as much power as you can safely and without damaging the engine. At this point it’s just a time thing; as they put more miles on tuned L5Ps and continue to familiarize themselves with the platform, you can be sure the potential of the custom tuning software will continue to improve.

If you’re currently driving an L5P and have been impatiently waiting for some real performance tuning to come to market, you’re probably already aware of some of this. For those of you who don’t spend every waking moment on social media, we hope this helps give you some insight. For further information, we suggest you contact HP Tuners or Duramaxtuner directly. These are exciting times for the GM performance camp, and we can’t wait to start seeing competition L5P-based builds to start popping up all over the country.

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