Now in private beta · 500 mechanics

Know what's actually wrong with your car — not just the code.

Plug in. Scan. Get a real diagnosis in plain English — ranked likely causes, step-by-step fixes, and what it actually costs. Built for mechanics who don't have time for guesswork.

Join the waitlist → See how it works
20,000+ DTCs covered
~60 sec plug-in to diagnosis
OBD2 '96+ vehicles
20,037
DTCs in database
~60 s
Plug-in to diagnosis
87 %
Top-cause accuracy
$0
Cost during beta
How it works

From plug-in to diagnosis in under 60 seconds.

No subscriptions to read codes. No "P0301 means cylinder 1 misfire" Wikipedia paste. Four steps, one real answer.

Step 01 ~5s

Plug in the adapter

Drop the OBD2 dongle into the port under your dash and turn the key. Pairs over BLE in seconds — no cables, no driver installs.

BLE 5.0OBD2 · 1996+
Step 02 ~12s
Reading modules7 of 9
PCM✓ 4 codes
Chassis✓ 0 codes
Bodyscanning…

Scan every module

Reads the PCM, chassis, body, and transmission controllers. Pulls active and pending codes plus freeze frame snapshots from the instant the fault tripped.

All modulesFreeze frame
Step 03 ~8s

Diagnose the cause

Cross-references the codes against your VIN, live sensor data, and 41M+ similar scans on the same engine. You get a ranked diagnosis with reasoning.

Ranked causesPlain English
Step 04 DIY · shop

Fix it confidently

Real part numbers, DIY effort estimates, and a confirmation procedure. Or hand the diagnosis to a shop and skip the $140 inspection fee.

OEM partsTime estimate
The difference

Code lookup is not diagnosis.

Every other OBD2 app translates a code into English. None of them tell you what's actually wrong. Here's the difference, on a real fault.

Other OBD2 apps

"P0301: Cylinder 1 misfire detected."

P0301 — Cylinder 1 Misfire Detected. The PCM has detected a misfire on cylinder 1 of the engine. A misfire is a failure of combustion to occur in one or more cylinders.
  • Repeats the code definition you already saw
  • Lists 12 generic causes with no ranking
  • No idea which is likely on your engine
  • "See a qualified mechanic" — you are the mechanic
FaultFinder

"Most likely a worn ignition coil — common on the L15B7 around 80–90k mi."

P0301 on a 2018 Civic 1.5T at 84k mi. Coil cyl 1: 64% likely (matches 41 similar scans, dry plug, STFT spike). Swap coil 1↔3 to confirm. 8 min, $46 OEM.
  • Engine-specific failure patterns
  • Ranked by likelihood with reasoning
  • Diagnostic procedure to confirm
  • Real part numbers and DIY estimate
What you get

A diagnostic instrument, not a code reader.

AI diagnosis

Plain-English explanations of every code, ranked likely causes with confidence scores, and engine-specific failure patterns.

Live data, all PIDs

5 Hz sensor stream — RPM, fuel trims, O2, MAF, MAP, every PID your ECU exposes. Out-of-spec values flagged inline.

Repair procedures

Step-by-step fixes with time estimates, tools needed, and the diagnostic checks to do at each step. Not a YouTube rabbit hole.

Cost estimates

Real DIY ranges, OEM and aftermarket part numbers, sourcing links, and shop comparison so you know what's fair.

Smog readiness

Track all 8 monitors and tell you exactly which drive cycles you still need before your inspection. Catch issues weeks early.

Scan history

Every scan saved per-vehicle. Spot intermittent faults, track repair progress, share a snapshot with the customer in two taps.

Built for working conditions

Strict severity. No guessing.

Mechanics need to read severity at a glance, in sunlight, possibly colorblind. Every fault is paired with an icon, label, and one of five colors — never used for anything else.

Critical
Do not drive
Catastrophic faults. Safety-critical DTCs. Park it.
Warning
Drive carefully
Most check-engine codes. Get it fixed soon.
Caution
Monitor
Pending codes. Soft warnings. Watch the trend.
OK
Cleared
Passed scans, healthy systems, all monitors green.
Info
Neutral
Informational, non-actionable readings.
Built for both

Whether you wrench for a living or a hobby.

For pros

Diagnose faster, work cleaner.

Stop re-reading the code book. FaultFinder ranks the likely failure on this engine — so your first swap is usually the fix.

  • Engine-specific failure patterns
  • Customer-ready PDF reports
  • Multi-vehicle history per shop
  • Bidirectional control on supported modules
For DIYers

The pro tool, in your driveway.

Don't pay $185 for a diagnosis you could do in your garage. Get a ranked answer, a step-by-step fix, and the part numbers you need.

  • Plain-English diagnoses
  • Step-by-step repair guides
  • OEM and aftermarket part links
  • Smog readiness coaching
Privacy by architecture

Your vehicle data stays yours.

Vehicle data is sensitive. Where you drove, when, and what's wrong with your car. We built FaultFinder so we never have a reason to know.

Read the architecture →

VIN-anonymized in transit

Your VIN is hashed before it ever leaves your phone. The AI sees make/model/year only — never anything that traces back to you.

Zero data retention on AI

Diagnostic queries run under a Zero Data Retention agreement with our AI provider. Processed and discarded, never used to train models.

Scan history is yours

Stored locally, encrypted. Export or delete anything in one tap. Nothing gets sold, ever — there's no ad business to feed.

No location, no telemetry

We don't track GPS, driving habits, or in-app behavior. Diagnostic queries are the whole product.

From the blog

Behind the scenes.

We're Looking for 5 Design Partners

FaultFinder is recruiting mechanics and DIYers to shape the product before launch. Free hardware, free app, weekly feedback calls. Here's how it works.

Read more →

Privacy by Architecture: How FaultFinder Protects Your Vehicle Data

Your vehicle data is sensitive. Here's how we built privacy into FaultFinder's architecture from day one — not as a policy, but as code.

Read more →

Why Code Lookup Is Not Diagnosis

Every OBD2 app on the market translates DTCs into English. None of them tell you what's actually wrong. Here's the difference — and why it matters.

Read more →
View all posts →

Get in line. Get there first.

Limited beta seats. Free hardware for design partners. Weekly product calls so you actually shape it.

No spam. Two emails total before launch.