What it means
A general electrical fault on the cylinder 1 combustion pressure sensor — used on engines with closed-loop combustion control (e.g. some Volvo and BMW direct-injection diesels) to measure cylinder pressure directly via a sensor at the glow plug or injector position.
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 so the control module can adjust combustion control. The module checks the sensor circuit for a usable signal. This code indicates a general electrical fault in the cylinder 1 sensor circuit, which may involve the sensor, connector, wiring, power, or ground.
Common causes
Most likely first.
- Cylinder 1 pressure sensor failure
- Damaged or corroded sensor connector
- Open or short in sensor wiring
- Fault in the sensor power or ground circuit
Symptoms
- Check engine light on
- Rough running or misfire
- Reduced engine power
- Hard starting
How to diagnose it
- Record freeze-frame data and review any available cylinder 1 pressure or combustion-control readings for dropouts or implausible values.
- Confirm from vehicle service information that the engine uses a cylinder 1 pressure sensor, then inspect its connector and nearby harness for damage, oil, corrosion, or loose pins.
- Check the sensor’s power and ground connections using the wiring diagram and manufacturer’s procedure.
- Test the cylinder 1 signal wire for opens or shorts and check connector pin fit before replacing the sensor.
- If the circuit checks out, test the cylinder 1 pressure sensor and its mounting according to the manufacturer’s procedure.
Common fixes
- Repair damaged wiring in the cylinder 1 pressure sensor circuit.
- Clean or repair corroded or loose connector terminals.
- Restore a sound power or ground connection to the sensor.
- Replace the cylinder 1 pressure sensor if it fails the specified test.
- Correct a confirmed sensor mounting problem.
Can I keep driving?
Rough running, misfires, reduced power, or hard starting may occur; avoid driving if the engine runs severely rough or loses power. Continued misfiring can damage the catalytic converter, and the vehicle may become difficult to restart.
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.