P21A7

Cylinder 12 Air-Fuel Ratio Imbalance

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$17–89 (est.)

Symptoms

Unstable engine operation
Power reduction
Increased fuel consumption
Check Engine light comes on
Misfire in cylinder 12

Causes

Dirty or faulty fuel injectors
Vacuum leak in cylinder 12
Problems with the ignition system (plugs, coils)
Oxygen sensor malfunction
Problems with the fuel pump or pressure regulator

How to Fix

Check the condition of the fuel injectors of the 12th cylinder
Investigate possible vacuum leaks
Check the spark plugs and coil of the 12th cylinder
Diagnose oxygen sensors
Check the fuel pressure in the system

Related codes

P21A6 P21A8 P0171 P0172