What it means
Cylinder-to-cylinder pressure variation on cylinder 8 is below the calibrated minimum — pressure stays unusually constant cycle-to-cycle, often a sign that the closed-loop combustion controller has lost authority or the sensor signal is filtered.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The ECM evaluates how cylinder 8 combustion pressure changes from cycle to cycle using the cylinder pressure signal. This code sets when the measured variation is below the calibrated minimum, meaning the signal or reported combustion pattern is unusually steady and may not reflect real combustion changes.
Common causes
Most likely first.
- Cylinder 8 pressure sensor or signal fault
- Pressure signal processing or filtering issue
- Cylinder 8 combustion control fault
Symptoms
- Check engine light on
- Reduced engine power
- Rough or uneven running
How to diagnose it
- Review freeze-frame data and compare cylinder 8 pressure variation live data with other cylinders under the same conditions.
- Inspect the cylinder 8 pressure sensor connector and harness for damage or poor contact that could suppress changes in the signal.
- Check the sensor signal for a fixed or excessively smoothed output while engine speed and load change.
- Test the cylinder 8 sensor supply, ground, and signal circuit against the manufacturer's specification.
- If the sensor and wiring pass, check for related combustion-control or signal-processing faults using available scan data and the manufacturer's diagnostic procedure.
Common fixes
- Clean and secure the cylinder 8 pressure sensor connector if poor contact is found.
- Repair damaged cylinder 8 sensor wiring or a faulty ground or supply connection.
- Replace the cylinder 8 pressure sensor if it fails the manufacturer's output test.
- Repair a confirmed cylinder 8 combustion-control or signal-processing fault.
Can I keep driving?
If the engine runs normally, drive gently and arrange diagnosis soon; avoid high loads until the cylinder 8 reading is verified. Rough running or power loss can affect drivability and emissions, so stop if symptoms become severe.
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.