What it means
Cylinder 1 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
On engines equipped with cylinder pressure sensing, the cylinder 1 pressure sensor measures combustion pressure for closed-loop combustion control. The control module checks that the reading changes plausibly as cylinder 1 operates. This code means the signal is present but its range or response does not match what the module expects.
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
- Record freeze-frame data and compare available cylinder 1 pressure readings with engine speed and operating conditions.
- Inspect the cylinder 1 sensor mounting, connector, and harness for looseness, corrosion, damage, or poor pin contact.
- Check the sensor’s power, ground, and signal circuit using the wiring diagram and manufacturer’s procedure.
- Compare cylinder 1 pressure data with other available cylinders or reference values to determine whether the fault follows the sensor or the cylinder.
- If wiring and mounting are sound, test the sensor response and inspect for a combustion or mechanical issue affecting cylinder 1.
Common fixes
- Secure the cylinder 1 pressure sensor if its mounting is loose.
- Repair damaged wiring or poor connector contact.
- Replace the cylinder 1 sensor if its response fails the manufacturer’s specification.
- Repair a confirmed cylinder 1 combustion or mechanical problem.
Can I keep driving?
If the engine runs smoothly, limit driving and avoid heavy loads until the fault is diagnosed; stop if it misfires severely or loses power. Ongoing misfire can damage the catalytic converter and may make starting harder.
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.