Faulty cylinder 2 pressure sensor; Damaged or corroded wiring or connector at the sensor; Open or short circuit in the sensor signal or reference voltage circuit; Failed sensor ground connection; Mechanical issue such as a loose sensor or carbon buildup affecting the sensor reading; Powertrain control module software or internal fault (less common)

DTC codes / P03xx · Ignition system and misfire / P039F

P039FCylinder 2 Pressure Sensor Circuit

Q: What does code P039F mean?

Cylinder 2 Pressure Sensor Circuit. P039F indicates that the powertrain control module has detected an abnormal signal from the cylinder 2 pressure sensor circuit, which is used on some engines to monitor combustion pressure for precise fuel and ignition control. The computer compares the sensor's voltage or signal pattern against expected values and sets this code when the reading falls outside the normal range or behaves erratically.

P039F indicates that the powertrain control module has detected an abnormal signal from the cylinder 2 pressure sensor circuit, which is used on some engines to monitor combustion pressure for precise fuel and ignition control. The computer compares the sensor's voltage or signal pattern against expected values and sets this code when the reading falls outside the normal range or behaves erratically.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Rough idle or misfire-like shudder that may be intermittent
Reduced engine performance or hesitation during acceleration
Poor fuel economy due to incorrect fuel delivery calculations
In rare cases, the engine may enter limp mode or stall

Common causes, most likely first

Faulty cylinder 2 pressure sensor
Damaged or corroded wiring or connector at the sensor
Open or short circuit in the sensor signal or reference voltage circuit
Failed sensor ground connection
Mechanical issue such as a loose sensor or carbon buildup affecting the sensor reading
Powertrain control module software or internal fault (less common)

How to diagnose and fix it

Perform a visual inspection of the sensor, connector, and wiring for damage or corrosion
Use a scan tool to check for related codes and freeze-frame data to confirm the fault conditions
Measure sensor resistance and voltage according to the manufacturer's specification
Check the signal circuit for continuity and shorts to ground or power
Verify the reference voltage and ground at the sensor connector
Replace the cylinder 2 pressure sensor if testing indicates it is faulty
Clear codes and perform a road test to verify the repair

Cylinder pressure sensor circuit pitfalls

A loose or backed-out sensor can cause erratic readings that mimic a failed sensor, so always check mounting torque before replacement.
Wiring harness chafing near hot exhaust components is a common hidden cause that visual inspection from above may miss.
This code can be set by a momentary glitch that does not affect driveability, so clearing and rechecking after a repair is essential.
On some engines, the cylinder pressure sensor is integrated into the glow plug or injector, making replacement more involved than expected.
A weak battery or charging system issue can cause voltage spikes that trigger false pressure sensor codes.

Can I keep driving with P039F?

The vehicle is generally safe to drive with this code if no severe symptoms are present, but avoid aggressive acceleration or heavy loads until diagnosed. If the engine runs rough, misfires, or enters limp mode, seek professional diagnosis promptly to prevent further damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.