OBD Codes List

Diagnostic reference · P03C2

P03C2

Cylinder 5 Pressure Too Low

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

What it means

P03C2 means Cylinder 5 Pressure Too Low.

Check these first

  • A leaking compression ring on cylinder 5
  • A burnt or poorly sealing exhaust valve on cylinder 5
  • A failed cylinder 5 pressure sensor reading low
  • An intake or exhaust leak at cylinder 5
  • Tight valve lash on cylinder 5

What to do next

  1. Run a compression test on cylinder 5 and compare to the rest
  2. Run a cylinder leakdown test on cylinder 5
  3. Compare the cylinder 5 pressure sensor to a known good one
  4. Check valve lash on cylinder 5
  5. Repair the valve or ring fault if the mechanical test confirms it
  6. Clear the code and retest

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Updated

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