Code
P2349
Generic
P — Powertrain
Cylinder 9 Pressure Sensor Circuit Range/Performance
AI status
Completed
Completed
100%
Causes
- Faulty cylinder 9 pressure sensor
- Open, short or intermittent wiring between sensor and ECM
- Poor connector contact (corrosion, pin damage, bent pins)
- Low or missing sensor reference voltage or ground
- Contaminated or oil-fouled sensor
- ECM input circuit fault or software anomaly
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Poor idle, rough running or misfire on affected cylinder
- Loss of power or uneven acceleration
- Reduced fuel economy and increased emissions
- Hard starting or extended cranking in some conditions
- Stored freeze-frame data showing abnormal sensor values
What to check
- Read freeze frame and live data with a capable scan tool; note cylinder 9 pressure sensor values and compare to other cylinders
- Verify code is current (not historical) and check for related codes
- Visually inspect sensor connector and wiring for damage, corrosion, pin push-out or oil intrusion
- Backprobe sensor connector to confirm reference voltage, signal voltage and ground with key ON and engine running as specified
- Measure wiring continuity and check for shorts to battery and ground
- Swap with a known-good identical sensor (if available) or measure sensor resistance/voltage per manufacturer spec
Signal parameters
- Sensor supply (reference) typically 5 V or 3.3 V from ECM — verify exact vehicle spec
- Signal output usually an analog voltage proportional to pressure (commonly ~0.5–4.5 V range) or CAN/serial data on some systems
- At key ON, engine OFF: expect stable reference and signal within manufacturer idle range; noisy/absent signal indicates circuit fault
- ECM input impedance: check for expected resistance per service information (varies by manufacturer)
Diagnostic algorithm
- Retrieve DTC, freeze frame and live data. Confirm P2349 and note any other stored codes.
- Inspect the cylinder 9 pressure sensor connector and harness for damage, oil or corrosion. Repair as needed.
- With a digital multimeter or oscilloscope, backprobe the sensor connector: verify sensor reference voltage, ground continuity and signal voltage. Compare readings to known-good values or published specs.
- Wiggle harness while monitoring live data to check for intermittent faults.
- Check continuity between sensor pins and the ECM pins; check for shorts to battery or ground.
- If wiring and connectors are good, bench-test or substitute the sensor with a known-good unit and recheck data for proper response across pressure range.
- If sensor substitution clears the code, replace the sensor and retest. If not, inspect/repair wiring or test ECM input circuit.
- If electrical circuits check good but pressure readings remain abnormal, perform mechanical diagnostics (compression/leakdown, valve train inspection) to rule out internal cylinder pressure issues.
- After repairs, clear codes and test drive to confirm code does not return and that live data behaves as expected.
Likely causes
- Damaged or contaminated pressure sensor at cylinder 9
- Broken or shorted harness/connector to cylinder 9 sensor
- Bad sensor ground or reference supply from ECM
- Intermittent connector contact (oil intrusion or corrosion)
- Less likely: internal ECM fault or extreme mechanical cylinder issue
Fault status
Status
Cylinder 9 pressure sensor circuit — signal out of expected range or poor performance detected by ECM.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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