What are the common causes of P234F?

A weak or failing fuel injector on cylinder 9. Low compression on cylinder 9 from worn rings or valves. A faulty cylinder pressure sensor for cylinder 9. Carbon buildup on the cylinder 9 injector or valves.

Check live misfire counts and fuel trims on cylinder 9. Run a compression and cylinder leak-down test on cylinder 9. Swap the cylinder 9 injector with a neighbor and watch the fault move. Inspect the cylinder pressure sensor wiring and connector. Test the cylinder pressure sensor signal against a known-good cylinder. Clear the code and retest.

P234F

Cylinder 9 Pressure Variation Low

System: Ignition and misfire (P code)
Lamp: Check Engine Light
Category: Powertrain - Ignition

What it means

P234F means Cylinder 9 Pressure Variation Low.

Check these first

A weak or failing fuel injector on cylinder 9
Low compression on cylinder 9 from worn rings or valves
A faulty cylinder pressure sensor for cylinder 9
Carbon buildup on the cylinder 9 injector or valves

What to do next

Check live misfire counts and fuel trims on cylinder 9
Run a compression and cylinder leak-down test on cylinder 9
Swap the cylinder 9 injector with a neighbor and watch the fault move
Inspect the cylinder pressure sensor wiring and connector
Test the cylinder pressure sensor signal against a known-good cylinder
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-08-30.