Medium urgency
SPN 4364 FMI 18
DEF quality or level – abnormal
Aftertreatment DEF (diesel exhaust fluid) quality or level fault. May trigger derate or warning.
View fault detailsTH
TruckHelpNowAI diagnostic workspace
Professional truck diagnostics with clearer next steps.
Describe symptoms, paste SPN/FMI fault codes, or upload a dashboard photo to get structured, safety-first guidance that is easy to scan from the cab or the shop floor.
Ready to startImage-aware
Diagnostic session
Start with a clear symptom summary, the truck details, or a dashboard photo.
Mobile readyStructured guidanceSafety first
Start a case
Built for practical roadside troubleshooting.
Capture the truck details, what changed, and any fault codes or dash warnings. The assistant will turn that into likely systems, low-risk checks, and safety-minded next steps.
Symptoms
Describe when the issue shows up: startup, idle, under load, regen, or highway speed.
Codes
Paste SPN/FMI or OEM fault codes so the assistant can anchor the diagnosis faster.
Photos
Upload a dashboard or scanner image if warning lights or code details are easier to show than type.
Suggested prompts
Or type below and your first message will create the case automatically.
What you will get
Likely system area
A clear read on what subsystem the symptoms point toward first.
Immediate checks
Low-risk inspection steps drivers or dispatch can use right away.
Safety guidance
Stronger stop-driving guidance when the symptoms suggest higher risk.
Describe the problem
Include truck details, symptoms, codes, or upload a dash/scanner image.
Enter to sendShift + Enter for a new linePNG, JPG, WebP up to 8 MB
Safety-critical issues should still be confirmed with a qualified technician.
What this page covers
Use the chat for truck fault codes, warning lights, and symptom-based troubleshooting
This page is built for real truck-diagnostic searches like truck fault code help, semi-truck warning light questions, and commercial truck troubleshooting when the issue still needs fast context before a shop visit.
Medium urgency
SPN 3710 FMI 2
DPF differential pressure – erratic or intermittent
DPF (diesel particulate filter) pressure sensor or circuit fault; can affect regen and derate.
View fault detailsHigh urgency
SPN 91 FMI 3
Engine speed – voltage high
Engine speed sensor signal out of range high. May cause no-start or erratic idle.
View fault detailsSupported entry pages
Brand pages for common heavy-truck diagnostic searches
TruckHelpNow also publishes focused brand pages for common search intent around Volvo, Freightliner, Kenworth, and International truck diagnostics.
Best SEO use of this tool
- Paste the exact fault code instead of only describing a light.
- Include when the symptom appears: startup, idle, regen, hill load, or highway speed.
- Upload a dashboard or scan-tool image when the code is easier to show than type.
FAQ
Questions drivers ask before opening a truck diagnostic chat
What should I include in a truck diagnostic chat?
Start with the truck year, make, model, engine, the exact symptom, when it happens, and any SPN/FMI or OEM fault codes shown on the dash or scanner.
Can I use TruckHelpNow for dashboard photo analysis?
Yes. The chat accepts dashboard and scan-tool images so the assistant can pull visible text, fault codes, and warning-light context into the response.
When should a truck be parked instead of driven farther?
Brake issues, steering concerns, severe overheating, fire risk, fuel leaks, wheel-end issues, and low-air warnings should be treated as stop-now events until the truck is verified safe.