What it means
Cylinder 4 pressure sensor signal jumps or drops out intermittently — connector or wiring issue. 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 reports combustion pressure to the engine control module, which uses the signal to assess that cylinder's combustion. This code sets when the cylinder 4 signal changes erratically or drops out intermittently rather than remaining stable and plausible.
Common causes
Most likely first.
- Intermittent connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check-engine light
How to diagnose it
- Review freeze-frame data and live cylinder 4 pressure readings to identify whether the fault appears at a particular engine speed, load, or vibration level.
- Inspect the cylinder 4 sensor connector for looseness, corrosion, moisture, damaged seals, or terminals that have lost tension.
- Follow the cylinder 4 sensor harness and check for chafing, poor routing, or contact with a vibrating engine component.
- Monitor the cylinder 4 signal while gently moving the connector and harness to reproduce a dropout or erratic reading.
- If the fault persists, test the sensor circuit for intermittent continuity and check its supply and ground connections using the manufacturer's procedures.
- If the circuit remains sound, compare the cylinder 4 sensor output with the manufacturer's specification and replace the sensor only if it is confirmed faulty.
Common fixes
- Reseat and secure the intermittent cylinder 4 sensor connector.
- Repair loose, corroded, or damaged connector terminals and seals.
- Repair chafed wiring and reroute or secure the harness away from vibrating components.
- Replace the cylinder 4 pressure sensor if testing confirms an intermittent internal fault.
Can I keep driving?
If the check-engine light is the only symptom, short, gentle trips may be possible, but the intermittent cylinder 4 signal can affect combustion control and emissions. Stop driving if rough running or power loss develops, and avoid heavy acceleration until diagnosed.
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.