P21A2

Cylinder 7 Air-Fuel Ratio Imbalance

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$17–89 (est.)

Symptoms

Unstable engine operation at idle
Reduced engine power
Increased fuel consumption
Check engine light comes on
Possible misfire in cylinder 7

Causes

Dirty or faulty injector of cylinder 7
Vacuum leak in the area of the 7th cylinder
Problems with the oxygen sensor or mass air flow sensor (MAF)
Malfunction of the fuel pump or fuel pressure regulator
Burnout of the exhaust valve in cylinder 7

How to Fix

Check the condition of the injector of cylinder 7, clean or replace if necessary
Inspect the intake tract for air leaks
Check the readings of the oxygen sensors and mass air flow sensor
Perform a compression test on cylinder 7
Check the pressure in the fuel system

Related codes

P0171 P0172 P0307