Heavy-Duty Diagnostics
Heavy-duty diagnostics across major engine, chassis, and aftertreatment systems. We chase fault codes to root cause — not just clear them and hope. The goal is a truck that's actually fixed, not a code that's temporarily reset.
What’s included
Everything covered under this service, on-road or in the shop.
- J1939 datalink scan
- OEM scan tool work — DDDL, Insite, Davie, ServiceMaxx, Premium Tech Tool
- ECM parameter read and program
- Active and stored fault code tracing
- Component-level voltage drop testing
- Compression and cylinder cutout tests
- Intermittent fault analysis with dataloggers
- Wiring harness and ground continuity testing
Why fleets and drivers choose T&T
OEM-level tools, not aftermarket readers
Generic readers see a fraction of what's on the datalink. Our OEM tools talk to every module the way the factory shop does.
Time logged on the diagnostic — you see what we did
Diag time is documented. You'll know what we tested, what we ruled out, and what the data showed. No black box.
If we can't find it, we don't charge for guesses
Some intermittent faults are genuinely hard. We'll tell you when we've hit the limit of what's findable instead of swapping parts in hopes.
Brands & systems we service
Detroit DDDLCummins InsitePACCAR DavieInternational ServiceMaxxAllison DOCMeritor TOOLBOXBendix AComWabco Toolbox
Frequently asked
- What does a diagnostic visit actually look like?
- We connect to the J1939 datalink, pull active and stored codes, log live data while running the symptom condition, and trace from there. Some issues resolve in 30 minutes. Some take a couple of hours of live-data analysis. We log what we do.
- Why does the same fault code keep coming back?
- Because clearing a code doesn't fix anything — it just resets the count. The code came back because the underlying cause is still there. We chase the cause.
- Can you program parameters in the ECM?
- Yes, for the platforms we have OEM tooling for — Detroit, Cummins, PACCAR, International. Some changes need OEM-level credentials we don't have; we'll tell you up-front when that's the case.
- Will you talk to my warranty shop after diagnosis?
- Yes. We'll provide written diagnostic notes, fault code printouts, and live-data logs to share with a dealership warranty department. Often that conversation is faster with our notes in hand.
- Can you diagnose if I bring the truck in just for that?
- Yes — diagnostic-only visits are common. You don't have to commit to the repair before the diagnosis.
Get a truck back on the road.
Call us — most customers reach a real person in under 30 seconds.