What it means
Cylinder 4 pressure sensor reads in range but plausibility check fails. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The cylinder 4 pressure sensor measures combustion pressure so the control module can assess that cylinder's performance. This code sets when the signal remains within an electrical range but fails the module's plausibility check, which may result from sensor drift or a loose mounting that alters the pressure response.
Common causes
Most likely first.
- Sensor drift
- Sensor element aged beyond calibration window
- Sensor mounting loose - signal damping
Symptoms
- Check engine light on
- Rough running or misfire
- Reduced engine power
- Hard starting
How to diagnose it
- Review freeze-frame data and compare cylinder 4 pressure readings with the other cylinders at the same engine speed and load.
- Check the live cylinder 4 pressure signal for readings that are electrically plausible but inconsistent with engine operation.
- Inspect the sensor connector and harness for corrosion, chafing, loose terminals, or poor contact.
- Check that the cylinder 4 sensor is properly seated and mounted according to the manufacturer's procedure.
- Test the sensor response and circuit against the manufacturer's specification before replacing parts.
Common fixes
- Secure the cylinder 4 pressure sensor mounting if it is loose.
- Repair corroded terminals or damaged wiring at the cylinder 4 sensor.
- Replace a drifting cylinder 4 pressure sensor if it fails the specified response test.
- Correct a related combustion fault if testing shows the sensor signal is accurate.
Can I keep driving?
If the engine runs smoothly, drive gently and arrange diagnosis soon. Avoid continued driving if cylinder 4 misfires or power drops, since poor combustion can increase emissions and damage the catalytic converter.
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.