Question 1

What does code P0420 mean?

Accepted Answer

P0420 means Catalyst System Efficiency Below Threshold. Before replacing the cat ($500-2,500), check the downstream O2 sensor first ($100-200).

Question 2

What does code P0171 mean?

Accepted Answer

P0171 means System Too Lean (Bank 1). Start by cleaning the MAF sensor — free and fixes this about 30% of the time.

Question 3

What does code P0300 mean?

Accepted Answer

P0300 means Random/Multiple Cylinder Misfire. If check engine light is flashing, misfires can damage the catalytic converter. New spark plugs fix this more than half the time.

Question 4

What does code P0128 mean?

Accepted Answer

P0128 means Coolant Thermostat Below Regulating Temperature. A $15-50 thermostat replacement fixes it in 95% of cases.

Question 5

What does code P0456 mean?

Accepted Answer

P0456 means EVAP System Very Small Leak. Try a new gas cap first ($10-25).

Question 6

What does code P1326 mean?

Accepted Answer

P1326 is a Hyundai/Kia safety recall code. Contact your dealer IMMEDIATELY — engine replacement is covered FREE under recall.

Question 7

What does code P0700 mean?

Accepted Answer

P0700 means Transmission Control System Malfunction. Read the companion transmission codes for the actual problem.

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