01Core
All Stored & Pending Codes
We pull every active, stored, and pending diagnostic trouble code (DTC) the engine control module is holding. Pending codes catch problems before the light even comes on.
Free check engine light scan.
Walk in, we plug in, you leave with a readout and a real answer. No appointment, no obligation, no upsell. Same scan most Greensboro shops charge 100 dollars for.
What a free scan actually includes.
A free scan at the parts store gets you a code printout. A free scan at M&K gets you context. Here is what is in the box.
02
Freeze-Frame Data
Snapshot of what the engine was doing the moment the code set: RPM, coolant temp, fuel trim, throttle position. Worth gold for misfire and lean-condition diagnostics.
03
Plain-English Readout
We tell you what each code means in normal language, what the likely cause is on your specific vehicle, and which codes are minor versus serious.
04
Readiness Monitor Check
Critical for NC inspection. If you recently cleared codes or replaced the battery, your monitors may not be set. We tell you whether you are ready to test.
05
Honest Verdict
Loose gas cap, lazy O2 sensor, or something serious? We tell you straight up whether you can drive home and schedule it, or whether you should leave the car with us today.
06
Written Quote, No Pressure
If you want us to do the repair, we will quote it in writing before we touch a wrench. If you want to take the diagnosis elsewhere or fix it yourself, that is fine. The scan was still free.
What you do not get at AutoZone or O'Reilly.
Parts-store scans are free and useful as a first look. But a code is a clue, not a verdict, and the parts-store reader leaves a lot on the table.
Live data and bidirectional control
Our scan tool reads live sensor data (fuel trims, O2 cross counts, ignition timing) and can command actuators (cycle a purge valve, fire an injector). The parts-store tool reads codes and stops.
Manufacturer-specific code databases
Generic OBD-II covers powertrain. Body, chassis, and network codes (B, C, U codes) need OEM-level software. We have it. The parts-store reader usually does not.
Diagnosis, not parts sales
The parts store is in the business of selling parts. The first answer they give will involve buying parts. We are in the business of fixing cars correctly, which sometimes means cleaning a sensor instead of replacing one.
Context from doing this all day
A P0420 on a 2008 Toyota Camry is almost always upstream O2 sensor. A P0420 on a 2015 Subaru Forester is almost always the catalyst. Pattern recognition only comes from a shop that sees these codes every week. We do.
No risk of misdiagnosis-driven parts spending
Nearly 30 percent of P0420 codes get misdiagnosed and result in unnecessary catalytic converter replacement. The wrong fix is more expensive than no fix. We rule things out before we recommend parts.
If you have already gotten a scan at O'Reilly or AutoZone, bring the printout in. We will tell you whether the suggested fix is right, partially right, or completely wrong before you spend on parts.
Already got your codes?
Look up what the code means, or read the urgent-symptom guide if the light is flashing.
01
Common OBD-II Codes Explained
P0420, P0171, P0300, P0455, P0128. What each code means and what a proper diagnosis looks like.
02
Check Engine Light On
Top 10 causes, solid vs flashing, and when to drive vs pull over. Plain-English guide.
03
Flashing Check Engine Light
Active misfire, urgent action. What is happening and what the repair looks like.
04
All Engine Diagnostics
Hub page. Full diagnostic process, what we test, and what to expect at the appointment.
Frequently asked.
Yes. We pull codes, hand you the readout, explain what they mean. No charge, no obligation to book repair work with us. We do this because earning trust upfront is cheaper than buying ads.
No. Walk in any business day, Monday through Friday 9 AM to 6 PM or Saturday 9 AM to 3 PM. If we are slammed we may ask you to wait or leave the car for an hour, but you will not pay for the scan either way.
Usually five to ten minutes from the time we plug in. Cars built before 1996 (pre-OBD-II) take longer and need OEM software. Newer European cars with CAN-bus gateway lockouts also take longer. We will tell you up front.
Both. The code is the starting point. We explain what triggered it, what the most likely cause is on your specific vehicle, and what the realistic repair looks like. Plain English, no jargon dump.
Yes. We have OEM-spec scan tools that read the full network on most European vehicles. Generic OBD-II often shows half the story on these cars. We see the rest.
We tell you, we quote the repair in writing, and we let you decide. You can book with us, take the diagnosis to another shop, or DIY it. The scan was free either way.
Yes. The engine control module holds historical codes for a number of drive cycles even after the light clears. We can often see exactly what triggered it.
Most charge 60 to 130 dollars for a basic diagnostic. We use the free scan as a way to start a relationship, not a profit center. If you trust the diagnosis you are more likely to trust us with the repair.
Got a code, want a real answer?
Walk in any business day. Free scan, plain-English readout, written quote if you want one.
1605 W Gate City Blvd
Greensboro, NC 27403
Mon–Fri · 9 AM – 6 PM
Sat · 9 AM – 3 PM
(336) 370-6710
Walk-ins welcome