What it means
Cylinder 9 pressure sensor above upper plausibility — open signal or short to B+. 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 9 pressure sensor sends combustion-pressure data to the engine control system. This code sets when its signal exceeds the calibrated upper limit, which can happen with an open signal path, a signal shorted to supply, or a failed sensor ground.
Common causes
Most likely first.
- Signal line shorted to supply
- Sensor ground open
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Reduced engine power
- Rough running or misfire
- Poor acceleration
How to diagnose it
- Save freeze-frame data and review live cylinder 9 pressure data for a reading stuck high or rising abnormally.
- Inspect the cylinder 9 sensor connector and harness for loose pins, corrosion, moisture, or wires rubbed through to a supply circuit.
- Check the sensor ground connection for an open or poor contact that could make the signal appear high.
- Test the cylinder 9 signal and ground circuits using the manufacturer's procedure to distinguish an open circuit from a short to supply.
- If the wiring and ground are sound, test the cylinder 9 pressure sensor for an internal fault.
Common fixes
- Repair an open signal wire or a short to supply in the cylinder 9 pressure-sensor circuit.
- Restore a sound cylinder 9 sensor ground connection.
- Repair corroded, loose, or damaged connector terminals.
- Replace the cylinder 9 pressure sensor if circuit checks show the sensor itself is faulty.
Can I keep driving?
Avoid hard acceleration if the engine runs roughly, misfires, or has reduced power; incorrect cylinder 9 pressure feedback can disrupt combustion control. Stop driving if misfiring becomes severe or the engine loses substantial power.
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.