What it means
Cylinder 1 pressure sensor below lower plausibility — short to ground. 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 monitors its signal and sets this code when the reading falls below the expected level. A short to ground, damaged wiring, or a poor connector contact can pull the signal low.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Rough running or misfire
- Reduced engine power
- Hard starting
How to diagnose it
- Record freeze-frame data and check available cylinder 1 pressure readings for a low or missing signal.
- Inspect the cylinder 1 pressure sensor connector and harness for chafing, moisture, corrosion, or a signal wire touching ground.
- Using the wiring diagram, check the sensor’s power and ground and test for a short to ground in the signal circuit as specified by the manufacturer.
- Check connector pin fit and circuit continuity while gently moving the harness to identify a poor contact or short.
- If the circuit passes, test the sensor output and its mounting before replacing the sensor.
Common fixes
- Repair the cylinder 1 sensor signal wire where it is shorted to ground.
- Replace damaged or chafed wiring in the sensor harness.
- Clean or repair corroded, loose, or pushed-back connector terminals.
- Replace the cylinder 1 pressure sensor if its output remains low with a sound circuit.
- Correct a confirmed sensor mounting problem.
Can I keep driving?
Rough running, misfire, reduced power, or hard starting may occur; avoid driving if the engine runs severely rough or cannot maintain power. Continued misfiring can damage the catalytic converter.
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.