Read the fault. Keep the evidence. Know what to verify next.

TruckDiag is an arrival-scan diagnostic reader for heavy-duty repair. When the truck is connected, it preserves the J1939 evidence with the repair event.

Ask about TruckDiag Inspect an arrival scan

Available on its own or as a DieselOS add-on. Beta preview; live-truck confirmation remains in progress.

Arrival scan · Unit 12

Offline-validated workflow

Capture complete
Engine #1 reported SPN 3936 / FMI 18 with an amber lamp. Raw evidence preserved.

Source ECUEngine #1address claim captured

SPN / FMI3936 / 18DM1 active

LampAmberreported in capture

Occurrences2current session

CaptureCompletetransport session closed

GuidancePossible causenot confirmed

Possible cause · SCR dosing conditionTechnician confirmation required

Read DM2 historyCheck whether the fault is active, recent, or recurring.

Compare live dataUse the OEM path and current readings before selecting a repair.

Record the test resultKeep the result with this repair event for the next visit.

Sources / provenanceCurrent vehicle scan · captured J1939 evidence · technician confirmation required

Observation first

Keep source ECU, SPN/FMI, lamps, occurrence count, and capture completeness together.

Verification before repair

A useful hypothesis names the next discriminating test. It is never a confirmed diagnosis.

Technician remains in control

TruckDiag does not select parts, prescribe a repair, or replace OEM procedures.

What it preserves today

Arrival-scan capture, J1939 decoding, raw provenance, and safety-bounded guidance.

What is still being validated

Windows decoder parity and live-truck confirmation. The reader does not claim universal OEM coverage.