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What does your
check engine code mean?

Enter your OBD-II code below for an instant diagnosis — causes, repair costs, safe-to-drive status, and a downloadable PDF report.

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Popular codes:
P0420

Catalyst System Efficiency Below Threshold (Bank 1)

Your catalytic converter is not functioning at the required efficiency level. This is one of the most common codes and affects your car's ability to reduce exhaust emissions.

Severity Moderate
🔎 Most Likely Causes
🛠 Recommended Fix Steps
💰 Estimated Repair Cost
$0 – $0
total estimated repair (parts + labor)
🚗 Safe to Drive?
🔩 Parts You May Need
PartEst. CostWhere to Buy
💬 Questions to Ask Your Mechanic
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Browse Common OBD-II Codes
Click any category to see the most common codes and their meanings.
P04XX
Emissions & Catalytic
Most common codes · P0420, P0401, P0442
P01XX
Fuel & Air Mixture
P0171, P0174, P0172
P03XX
Ignition & Misfire
P0300, P0301, P0302
P01XX
Cooling & Thermostat
P0128, P0125, P0117
P05XX
Idle & Speed Control
P0505, P0506, P0507
P03XX
Camshaft & Crankshaft
P0340, P0335, P0341
P01XX
Oxygen Sensors
P0135, P0141, P0155
P07XX
Transmission
P0700, P0715, P0730

Frequently Asked Questions

What is an OBD-II code?

OBD-II (On-Board Diagnostics) codes are standardized fault codes that your car's computer generates when it detects a problem. They start with a letter (P, B, C, or U) followed by 4 digits. P codes relate to the powertrain (engine and transmission).

How do I read my OBD-II code?

You need an OBD-II scanner. You can buy one for $20–$30 on Amazon, or most AutoZone, O'Reilly, and Advance Auto Parts stores will read your code for free if you bring your car in.

Can I drive with a check engine light on?

It depends on the code. Some codes (like P0420 for a faulty catalytic converter) are safe to drive short distances. Others (like P0300 for engine misfires) can cause serious engine damage if ignored. Look up your specific code above to see the safe-to-drive status.

How accurate are the repair cost estimates?

Our estimates are based on average labor rates ($80–$150/hour) and typical parts costs across the US. Actual costs vary by location, vehicle make/model/year, and which mechanic you choose. Use these as a baseline when getting quotes — if a shop quotes significantly higher, get a second opinion.