Check engine diagnostics
Find out why the light is on before you pay for a repair.
What is your car doing?
Prefer to talk?Call (571) 749-1731
We read the codes, then test the part behind them, so you are not paying to replace parts on a guess. You get the cause and the price before any work starts.
When you may need this service
- The check engine light is on, or flashing
- Rough idle, stalling or hesitation
- Worse gas mileage than usual
- The light went out and came back
- An emissions test is due with the light on
Services available
- Read the codes the car has stored
- Test the part behind the code before anything is replaced
- Check live data and wiring when the code is not the whole story
- Give you the cause and the price before any work starts
How it works at John's.
No surprises. You know what it needs and what it costs before we start.
- 1
Tell us what is going on
Request a time here, call, or use our after-hours drop-off.
- 2
We find the cause
We test before we replace, then show you what we found.
- 3
You say yes first
The price comes broken down. Nothing gets done without your yes.
A good shop earns your trust.
5.0 155 reviews on GoogleQuestions people ask
What does it mean when my check engine light is on?
The light points to a system, not a part. Solid means get it checked soon. Flashing means stop driving and call us. Common causes are a loose gas cap, an oxygen sensor or a misfire. We test before we replace anything, so you only pay for the part that failed.
Can I keep driving with the check engine light on?
If it is flashing, no. Pull over and call us, because driving can ruin the catalytic converter. If it is solid and the car drives normally, it is usually safe to drive in soon. Do it before your emissions test is due.
Will my car pass inspection with the check engine light on?
No. In Fairfax County, Lorton included, cars need an emissions test every two years, and a lit check engine light fails it. Virginia safety inspection is every year. We do both, so bring it in, we find what set the light, fix it, and get you through.
