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Automotive HD/Fleet Forum

Professional automotive forum for discussion of heavy-duty trucks, buses and other on- and off-road equipment, and maintenance of automotive fleet vehicles. Discussion topics include fuels and lubricants, hydraulics, performance, on-board diagnostics, powertrain, power distribution, anti-lock braking and stability control systems, and best practices as they relate to heavy duty and fleet maintenance. This forum is for experienced automotive repair professionals only, membership required.

Continue to the description of our next automotive discussion forum, the HVAC Forum.

Recent Automotive Discussions in the Automotive HD/Fleet Forum

QLS Blues
05/30/2025 in the HD/Fleet Forum
Hi Everyone, Happy Friday! I have a 2017 Freightliner M2 Grade all for a local city here. It has a failed QLS and are on backorder for 2-3 months. P#04-35960-000. NO ONE in the country has one. Does anyone know what exactly goes wrong with them? Can somet...
Long crank hard start
05/30/2025 in the HD/Fleet Forum
[Driveability: 13 Mack GU8 GU800 12.8L] I have a Mack with a long crank/hard start issue... There are times I think the starter is going to burn up before starting and the next day, it fires up line a new truck. I have had it sitting for a week and it fi...
High press fuel system
05/22/2025 in the HD/Fleet Forum
[Driveability: 19 Ford F-550 Super Duty 6.7L] Group, This truck had a fuel system replaced 7 months ago, cust complains of power loss, however cleared all codes before bringing it. I can't duplicate his problem, we are on pretty flat ground here so it's ...
Isuzu shifting
05/19/2025 in the HD/Fleet Forum
Hi HD!!! Here is a doozy for all you Isuzu aficionados. And, we do consider us pretty well versed on Isuzu but this one is leading us astray. 2018 NPR. Nothing fancy. Aisin transmission. 2 years ago trans failed. BANGING into 3rd gear, no reverse. Pressur...
Irrational PX-9
05/19/2025 in the HD/Fleet Forum
Hello Everyone, I have a 2016 KW T370 with a PX-9 ESN 7392675. (418 K on the odometer) Came in on the hook with engine no run condition. Scanned and found active DTC 0272- engine fuel pressurization shorted to high (1 count), inactive 4726- engine fuel le...

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