Engine

P039F — Cylinder 2 Pressure Sensor Circuit Fault

Severity: medium Drive with care, to a shop

What P039F means

P039F means the engine control module has found a problem in the circuit of the cylinder 2 pressure sensor, also called a combustion pressure sensor. This sensor reports what is happening during combustion so the ECM can fine-tune ignition and fueling. If the signal is open, shorted or out of range, the ECM sets the code and turns on the check engine light.

Symptoms

  • Check engine light on
  • Rough or unstable idle
  • Reduced power and sluggish acceleration
  • Higher fuel consumption
  • Possible misfires on cylinder 2
  • Increased emissions

Possible causes

  1. Failed cylinder 2 pressure sensor
  2. Damaged sensor wiring: open, chafed or shorted
  3. Corroded or loose connector
  4. Engine mechanical problem such as abnormal compression
  5. Faulty ECM (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and look for misfire codes
  2. Inspect the cylinder 2 sensor harness and connector for damage, moisture and corrosion
  3. Check sensor power, ground and signal wires against the factory wiring diagram
  4. Test the wires for opens and shorts to ground or voltage
  5. Compare the sensor signal with other cylinders using a scan tool or scope
  6. Run a compression test on cylinder 2 if the electrical side is good
  7. Suspect the ECM only after the wiring and sensor are cleared

Common fixes

  • Replace the cylinder 2 pressure sensor
  • Repair the wiring harness or replace damaged connectors
  • Fix the mechanical cylinder problem if confirmed
  • Repair or replace the ECM and perform any required programming

Questions and answers

What does P039F mean?

It is a fault in the cylinder 2 pressure sensor circuit. The ECM is getting a wrong signal or none at all.

Can I drive with P039F?

Short, gentle trips to a shop are usually fine. If the engine shakes or the check engine light flashes, stop to avoid damaging the catalytic converter.

How do I fix P039F?

Start with the sensor wiring and connector, then the sensor itself. If both are good, check compression and only then consider the ECM.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.