P0397
Cylinder 1 Pressure Sensor Circuit Low
Cylinder pressure sensor
Generic OBD-II
Medium
What it means
P0397 means the cylinder 1 combustion-pressure sensor circuit is reading abnormally low. This sensor (found on certain engines) lets the computer monitor combustion, so a fault mainly sets the light and can limit related strategies rather than stopping the engine — usually caused by wiring or the sensor itself.
Medium
Can I keep driving? Usually drivable — this is a monitoring sensor, so the engine typically runs, though performance/emissions strategies may be limited.
Common symptoms
What you'll notice
- Check-engine light on
- Often no obvious change in how the car drives
- Possible reduced performance if the ECM limits functions that rely on the sensor
- May fail related monitors/emissions checks
Common causes
Most likely first
- Faulty cylinder 1 combustion-pressure sensorLikely
- Open or short-to-ground (low) in the sensor wiringCommon
- Corroded or loose connector at the sensorCommon
- ECM fault (less likely)Less often
How to diagnose & fix
Work through it in order
- Inspect the cylinder 1 pressure sensor connector and wiring for a short to ground or open.
- Compare the sensor's reading to the other cylinders' sensors on a scan tool.
- Verify the sensor's supply voltage and ground.
- Replace the cylinder 1 pressure sensor if it is out of spec, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0397?+
Generally yes — it's a diagnostic/monitoring sensor rather than a component the engine needs to run, but have it checked so you don't lose the functions it supports.
Can I just clear P0397?+
It will return if the wiring or sensor fault remains. Repair the circuit first.
Related codes
Often seen with P0397
Read & clear P0397 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX