What it means
Cylinder 1 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 1 pressure sensor tracks combustion pressure from one engine cycle to the next, and the control module checks that its signal remains consistent. This code sets when the signal from cylinder 1 drops out or changes erratically, often as a loose connection or vibrating harness interrupts it.
Common causes
Most likely first.
- Intermittent connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Intermittent rough running or misfire
- Intermittent loss of engine power
- Possible stalling or hard starting
How to diagnose it
- Use a scan tool to save freeze-frame data and watch the cylinder 1 pressure signal while the fault is present, noting any sudden dropouts.
- Inspect the cylinder 1 sensor connector for looseness, corrosion, moisture, damaged seals, or pins that are not fully seated.
- Check whether the cylinder 1 harness rubs against or vibrates with nearby engine parts, and look for worn insulation.
- With live data displayed, gently move the harness and connector to see whether the cylinder 1 reading changes or the fault returns.
- Test the cylinder 1 sensor signal, power, and ground circuits for intermittent continuity or contact problems against the manufacturer's specification.
Common fixes
- Reseat and secure the cylinder 1 sensor connector.
- Clean corroded connector contacts or replace damaged terminals.
- Repair chafed wiring and secure the harness away from vibrating parts.
- Replace the cylinder 1 pressure sensor if its signal remains erratic with sound wiring.
Can I keep driving?
If the engine is running smoothly, a short, gentle drive may be possible, but avoid high loads and stop if it misfires, loses power, or stalls. Intermittent readings can disrupt combustion control and may cause a stall.
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.