What it means
A general electrical fault on the cylinder 5 combustion pressure sensor — used on engines with closed-loop combustion control (e.g. some Volvo and BMW direct-injection diesels) to measure cylinder pressure directly via a sensor at the glow plug or injector position.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The cylinder 5 combustion pressure sensor measures pressure in cylinder 5 for the engine's combustion-control system. This code indicates a general electrical fault in the cylinder 5 sensor circuit, which may involve the sensor, its connector, wiring, supply, or ground.
Common causes
Most likely first.
- Cylinder 5 pressure sensor failure
- Damaged or corroded sensor connector
- Open or shorted sensor wiring
- Fault in the sensor supply or ground circuit
Symptoms
- Check-engine light
- Rough or uneven engine running
- Misfire or hesitation
- Reduced engine power
How to diagnose it
- Review freeze-frame data and all related sensor or circuit codes to determine when the cylinder 5 pressure sensor fault occurs.
- Inspect the cylinder 5 sensor connector for corrosion, moisture, loose fit, damaged seals, or pushed-back pins.
- Trace the cylinder 5 sensor wiring for opens, shorts, chafing, or damage near the engine and harness supports.
- Check the sensor supply and ground connections using the wiring diagram and manufacturer's procedures.
- Test the cylinder 5 sensor circuit and compare its output with the manufacturer's specification.
- If the wiring and connections pass, replace the sensor only if testing confirms an internal failure; investigate the control module only after the circuit is verified.
Common fixes
- Reconnect and secure a loose cylinder 5 pressure sensor connector.
- Repair corroded connector terminals or damaged seals.
- Repair an open, shorted, or chafed section of cylinder 5 sensor wiring.
- Restore a faulty sensor supply or ground connection.
- Replace the cylinder 5 pressure sensor if circuit tests confirm it has failed.
Can I keep driving?
The check-engine light may be the only immediate symptom, but the engine may lose reliable pressure information for cylinder 5 and run poorly. Avoid heavy loads if rough running or hesitation develops, and have the circuit checked soon to limit drivability and emissions problems.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.