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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

Exhaust fluid quality poor message
01/08/2026 in the HD/Fleet Forum
[Driveability: 15 Chevrolet Silverado 2500 HD LT 6.6L] replaced the def injector for a def problem, cleared codes and ran the processes with the scanner to get back to normal, but I can't get the poor quality message and the 60 miles to 65 mph speed lim...
starter engages on it's own
12/04/2025 in the HD/Fleet Forum
[Electrical: 01 GMC C6500 Topkick C6H042 7.2L] Dear sirs, I need your help with sending me a wiring diagram for the starter circuit on this truck. It has a 3116 Cat engine w/a M.T.. Prod.date is 09/00 and I am not sure what mods have been done. The truck...
2013 Ford E450 leaf spring R&R
12/01/2025 in the HD/Fleet Forum
Can't seem to figure out how to reinstall the leaf spring. It has some sort of goofy rear shackle, with a long spring box/bracket that faces forward with a bolt and spacer underneath the spring pack. In the rear, there is some sort of dual rubber blocks t...
K-Line Diag on 24v Modules
11/25/2025 in the HD/Fleet Forum
[Electrical: 14 Kenworth K370 6.7L] Have this K370 Euro 5 vehicle, truck will not start, ground from VIC3-L drops out to start relay when attempting to crank. Try scanning the truck with Davie4 and no come to any K-line modules the cluster and abs module...
No Crank
11/25/2025 in the HD/Fleet Forum
[Electrical: 16 Blue Bird All American FE AAC2810-3006 6.7L] Have this blue bird bus, truck would run and drive by jumping the starter. Ground signal was coming from key switch into the body module but nothing out. Disconnected the module load tested pow...

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