What it means
A general electrical fault on the cylinder 6 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
The cylinder 6 pressure sensor measures combustion pressure in cylinder 6 for engines that use cylinder-by-cylinder combustion control. P03C7 indicates a general electrical fault in that sensor circuit, so the controller cannot rely on the cylinder 6 pressure signal.
Common causes
Most likely first.
- Cylinder 6 pressure sensor failure
- Damaged or corroded sensor connector
- Open or shorted sensor wiring
- Fault in the sensor supply or ground circuit
Symptoms
- Check-engine light
- Rough or uneven engine running
- Misfire or hesitation
- Reduced engine power
How to diagnose it
- Confirm P03C7 and record freeze-frame data, then check for other cylinder 6 pressure-sensor or misfire codes.
- Locate the cylinder 6 pressure sensor from vehicle service information and inspect its connector for corrosion, damage, or a poor fit.
- Trace the cylinder 6 sensor wiring and check for opens, shorts, chafing, or damage to the supply and ground wires.
- Use a scan tool to review the cylinder 6 pressure signal and test the supply, ground, and signal circuits according to the wiring diagram.
- If the wiring and connector meet the manufacturer's checks, test the cylinder 6 pressure sensor and replace it only if it fails.
Common fixes
- Reconnect and secure a loose cylinder 6 pressure-sensor connector.
- Clean or repair corroded terminals and damaged connector seals.
- Repair an open, shorted, or chafed sensor wire, or restore a faulty supply or ground connection.
- Replace the cylinder 6 pressure sensor if circuit tests pass and the sensor itself is faulty.
Can I keep driving?
If only the check-engine light is on and the engine runs normally, limit driving and arrange diagnosis. Stop driving if it develops a misfire or significant power loss, because combustion control may not have reliable cylinder 6 pressure data.
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.