Is this car tuned?
Free. No account. The VIN is never stored.
Engine module
Software ID DEMOCAL-ECM-0412
- This car’s fingerprint
- What 14 of 15 other cars on this software report
- 5C3A91E7
Signs of changed engine software
Same software ID, different fingerprint: this car isn’t running the program the other 14 cars run.
Example with made-up numbers from a demo car.
Find out whether a car’s engine software was changed (tuned, remapped or chipped) before you buy it. Plug an OBD adapter into the car and we compare the fingerprint its engine computer reports with other cars running the same software. It only reads. Nothing in the car is changed.
Cars built for the US since 2005 have to report this fingerprint. Cars built for other markets may not.
What you need
- 1
An OBD adapter
An ELM327-type adapter with Bluetooth Low Energy, or a USB one for a laptop. Which ones work
- 2
Chrome on Android, or a laptop
iPhone browsers can’t talk to Bluetooth adapters. You can type the numbers in from a scan app instead.
- 3
The car, ignition on
The port is usually under the dashboard, near the steering wheel. The engine can stay off.
What the check reads
- Software ID (CAL ID)
- The name of each module’s program, set by the carmaker.
- Fingerprint (CVN)
- A code the car calculates from that program. Change the program and the code changes.
- VIN
- Tells us the make, model and year. We never store it.
- Check-engine light and fault codes
- Stored, pending and permanent codes. Permanent codes stay until the car’s own test passes.
- Readiness tests
- Which emissions self-tests have finished. Clearing codes restarts them.
- Since codes were cleared
- Warm-ups and distance since someone last cleared the codes.
Other ways to tell if a car has been tuned
Tuned, remapped and chipped all mean the same here: the engine computer’s software was changed. No single check is perfect, so use more than one before you buy. The full guide
- Ask, and read the paperwork
- Receipts from a tuning shop, or a tuning device left in the glovebox, are the clearest sign.
- Read the fingerprint
- What this check does: the software ID and its fingerprint, compared with other cars on the same software.
- Ask a dealer
- The carmaker’s own tools see more than any adapter. It costs a diagnostic fee, and it’s the check that matters for warranty.
- Pay a tuning shop to read the whole program
- They compare it with the factory file and see exactly what changed. The most thorough, and the slowest.
- Not much use on their own
- How the car feels on a test drive, a basic code reader, or aftermarket parts. They hint, they don’t prove.
More free car tools
- VIN checkMake, model, engine and factory from the VIN, plus every recall, owner complaint and crash rating NHTSA has for that model year.
- Fault code explainerWhat a code like P0420 means: the system, the area, and the official title for common generic codes.
- Adapter testChecks that your OBD adapter talks to this site before you go and see a car.
- Software ID lookupWhat other cars report for a calibration ID (CAL ID): how many, and which fingerprints.
- Type in a CAL ID and CVNAlready read the car with another scan tool or app? Compare the numbers here.
Why buyers check
Warranty
Dodge refused a roughly $36,000 engine repair on a 790-mile Challenger Hellcat after its engineers found non-factory software, and says a reflash leaves a permanent mark even after going back to stock. Autoblog, Motor Biscuit
Insurance
After a crash, a UK insurer voided a policy because of an undeclared engine remap, and the Financial Ombudsman found that fair. Financial Ombudsman
Smog check
California’s smog check compares these same two codes, and a car with modified software has to go back to stock or approved software to pass. California BAR
What it can’t tell you
- A car flashed back to stock reports the factory fingerprint again. The carmaker may still have a record of the flash.
- Some tuning tools rewrite the fingerprint to look factory (a “CVN fix”). What that is
- We judge a car only once 3 other cars with the same software agree. Until then the answer is “not enough data yet”.
- California’s rules require the fingerprint on 2005 and newer cars. European rules don’t, so cars built for other markets may not report one.
So the answer is “signs of changed software”, “no sign of tuning found” or “not enough data yet”, never “not tuned”. How it works