Cylinder Pressure Sensor Circuit Low (Bank 1)
The P0397 code means the vehicle's onboard diagnostic system has detected: Cylinder Pressure Sensor Circuit Low (Bank 1). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $200 - $800 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Engine may retard timing excessively
- Power loss
- Possible rough running
Probable Causes (Ranked by Likelihood)
- Short to ground in pressure sensor wiring Very High
- Failed sensor (shorted) High
- Connector corrosion Moderate
- PCM input fault Low
Step-by-Step Diagnostic Procedure
-
Read sensor voltage. Below minimum spec confirms low circuit.
-
Check for wiring short to ground.
-
Inspect connector.
-
Replace sensor if internally shorted.
Frequently Asked Questions
What causes circuit low on a cylinder pressure sensor?
A short to ground in the wiring or an internally failed sensor producing a low voltage signal.
Can P0397 cause engine knock?
If the PCM uses this sensor for knock control and it reads low, the PCM may not detect knock correctly, potentially allowing damaging detonation.
How is this sensor different from a MAP sensor?
A cylinder pressure sensor measures pressure inside the combustion chamber during the compression and power strokes. A MAP sensor measures intake manifold pressure.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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