What are the common causes of P21A6?

A dirty or clogged fuel injector on cylinder 11. A short or open in the cylinder 11 injector wiring. Corrosion at the cylinder 11 injector connector. A failed fuel pressure sensor. Low compression on cylinder 11.

Read the cylinder 11 fuel trim on a scan tool. Test the cylinder 11 injector pulse and wiring. Swap the cylinder 11 injector and see if the fault follows. Check the fuel pressure and its sensor. Run a compression test on cylinder 11. Clear the code and retest.

P21A6

Cylinder 11 Air-Fuel Ratio Imbalance

System: Fuel and air metering (P code)
Lamp: Check Engine Light
Category: Powertrain - Fuel/Air Metering

What it means

P21A6 means Cylinder 11 Air-Fuel Ratio Imbalance.

Check these first

A dirty or clogged fuel injector on cylinder 11
A short or open in the cylinder 11 injector wiring
Corrosion at the cylinder 11 injector connector
A failed fuel pressure sensor
Low compression on cylinder 11

What to do next

Read the cylinder 11 fuel trim on a scan tool
Test the cylinder 11 injector pulse and wiring
Swap the cylinder 11 injector and see if the fault follows
Check the fuel pressure and its sensor
Run a compression test on cylinder 11
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.