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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

KW T370, Code present, derate warning on dash, no MIL
06/17/2026 in the HD/Fleet Forum
2022 Kenworth T370, PX9/L9 VIN [...] This truck initially came in for MIL, Derate 3725, aftertreatment 1 intake NOX sensor abnormal rate of change. 15685, brake switch, abnormal update rate, a couple of codes for running the DEF level too low, and some co...
2020 kw t370 a/c
06/13/2026 in the HD/Fleet Forum
I need a connector pin out and schematic for the ac control head panel. It has an eight pin and a 16pin connector on the back. Any help would be greatly appreciated. I am now retired and don't have access anymore. Not having any luck on the web. It doesn'...
TCM repair
06/12/2026 in the HD/Fleet Forum
Has anyone used Circuit Board Medics for Duramax TCM repairs or anything ecm repairs the one we are working on is obsolete Gm has no stock left getting hard to find parts for some of theses older rigs anymore my local parts guy sent mine off but when it c...
2005 max forc dt wiring issue
05/19/2026 in the HD/Fleet Forum
[Electrical: 05 IC Corporation CE Integrated 7.6L] Got this bus that sat for the winter, went to start and no start. started with mo crank and found ign fuse blown. then would crank but not start. Found the 10 amp fuse for idm relay blown, replaced fuse ...
DD5 power issue
05/05/2026 in the HD/Fleet Forum
Not my buses, I don't run these but one of my association's member school districts is asking for help: Hi all! I hope everyone is enjoying this beautiful weather today. Is anyone having trouble with the DD 5 Detroit engines with fault codes for the high/...

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