Top 10 Cheapest OBD2 Codes to Fix (And Average Repair Cost)

Seeing the Check Engine Light often makes drivers worry about expensive repairs.

But here’s good news:

➡️ Many OBD2 trouble codes are actually cheap and simple to fix.

In many cases, the repair costs less than a normal service visit — especially if diagnosed early.

This guide covers the most common low-cost OBD2 codes and their typical repair prices.

1️⃣ P0455 – EVAP System Large Leak

One of the easiest and cheapest fixes.

Most common cause:

• Loose or damaged gas cap

Average repair cost:

• $20 – $60 (new gas cap)

Many drivers fix this code in minutes.

2️⃣ P0442 – EVAP System Small Leak

Usually caused by:

• cracked EVAP hose

• weak gas cap seal

• small vapor leak

Average repair cost:

• $50 – $200

Often detected during smoke testing.

3️⃣ P0128 – Coolant Thermostat Performance

Very common in colder climates.

Symptoms:

• engine warms slowly

• poor cabin heat

• lower fuel economy

Typical fix:

• thermostat replacement

Average cost:

• $150 – $400

4️⃣ P0101 – MAF Sensor Performance

Good news:

Many times the sensor only needs cleaning.

Repair options:

• MAF cleaning: $20 – $50

• replacement: $150 – $350

Very common beginner-level repair.

5️⃣ P0171 – System Too Lean

Often scary for drivers — but frequently simple.

Common causes:

• vacuum leak

• dirty MAF sensor

• loose intake hose

Average repair cost:

• $50 – $300

Early diagnosis saves money.

6️⃣ P0172 – System Too Rich

Usually caused by:

• dirty air sensor

• clogged air filter

• small fuel system issues

Average cost:

• $100 – $300

Ignoring it can become expensive later.

7️⃣ P0301 – Cylinder 1 Misfire

Specific cylinder misfires are often affordable.

Most common fixes:

• spark plugs

• ignition coil

Average repair cost:

• $100 – $350

8️⃣ P0302 – Cylinder 2 Misfire

Nearly identical to P0301.

Mechanics often swap coils to confirm diagnosis.

Cost:

• $150 – $400

9️⃣ P0303 – Cylinder 3 Misfire

Common on 4-cylinder engines.

Usually ignition-related.

Average cost:

• $150 – $400

🔟 P0304 – Cylinder 4 Misfire

Another highly common misfire code.

Often fixed with:

• new plugs

• new coil

Typical repair:

• $100 – $350

Quick Comparison Table

Why Cheap Repairs Become Expensive

Many simple codes become expensive only because drivers wait too long.

Example:

• small misfire → catalytic converter failure

• vacuum leak → engine damage

Early repair = lower cost.

How to Save Money on OBD2 Repairs

Best strategy:

✔ Scan the code early
✔ Fix simple problems first
✔ Avoid replacing random parts
✔ Start with airflow and ignition checks

Many repairs are easier than drivers expect.

FAQ

What is the cheapest OBD2 code to fix?

EVAP codes like P0455 are often the cheapest.

Can I fix OBD2 codes myself?

Many codes (gas cap, MAF cleaning, spark plugs) are DIY friendly.

Are all check engine lights expensive?

No — many are inexpensive if fixed early.

Final Thoughts

Not every Check Engine Light means expensive repairs.

Many common OBD2 codes are simple and affordable to fix — especially when diagnosed early.

Understanding which codes are cheap helps drivers avoid unnecessary stress and save money.