Diagnostic article Generic OBD-II
P0397: Cylinder 1 pressure sensor circuit low
The documented Mazda P0397 procedure covers cylinder 1 pressure sensor circuit low.
Read before applying this article
Documented application
Mazda3 workshop manual 01/2019 onward, d9n1-1a-22d_ver10; PCM (SKYACTIV-X). Verify exact vehicle specification; this is a Mazda application example.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P0397 identifies a low electrical input from cylinder pressure sensor number 1 on Mazda's SKYACTIV-X engine. The PCM threshold is 0.29 V or below for five seconds.
Low signal is different from low compression
This code describes the sensor circuit's electrical output. It does not directly measure whether cylinder 1 has adequate mechanical compression. Mazda lists a grounded supply or signal, a short between signal and ground, an open supply or signal, connection trouble and a failed sensor among the possible causes.
The presence of other low-input pressure-sensor faults changes the factory route. P03A1, P03AB or P03B5 sends the flow toward the PCM-connection branch rather than treating number 1 as an isolated sensor failure. Multiple channels therefore deserve attention before several sensors are condemned independently.
Establish the circuit and component evidence
For an isolated concern, Mazda evaluates the number 1 connection and sensor resistance, then the PCM connection and circuit paths. It also distinguishes a component resistance check from a later function check; passing one does not replace the other.
The response inhibits EGR and SPCCI, stops combustion feedback and retards ignition. Confirmation uses the prescribed key-on or running self-test and another pending-code inspection. Preserve the full cylinder-pressure code pattern and use the exact professional sensor procedure; this DTC supplies no basis for invasive engine work or a guessed pressure threshold.
Documented application
Mazda3 workshop manual 01/2019 onward, d9n1-1a-22d_ver10; PCM (SKYACTIV-X). Verify exact vehicle specification; this is a Mazda application example. Mazda factory diagnostic page, mirrored by CHARM.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
Cylinder 1 Pressure Sensor Circuit Low
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT