Cylinder Pressure Sensor Circuit Intermittent (Bank 1)
The P0399 code means the vehicle's onboard diagnostic system has detected: Cylinder Pressure Sensor Circuit Intermittent (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
- Intermittent Check Engine Light
- Occasional power reduction
- Random timing retard events
- Engine performance varies
Probable Causes (Ranked by Likelihood)
- Loose cylinder pressure sensor connector Very High
- Intermittent wire break High
- Sensor failing under heat or vibration Moderate
- PCM input intermittent Low
Step-by-Step Diagnostic Procedure
-
Monitor sensor signal during driving for dropouts.
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Wiggle test on connector and wiring.
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Check connector pins for looseness.
-
Test during various thermal conditions.
Frequently Asked Questions
How do I find an intermittent pressure sensor fault?
Record sensor data while driving and review for momentary signal dropouts or spikes that do not match engine operating conditions.
Can engine vibration cause P0399?
Yes, vibration can worsen a marginal connector or cracked wire, causing intermittent signal loss.
Should I replace the sensor or repair wiring?
Diagnose first. If the connector is the issue, repair it. If the sensor output is erratic even with a good connection, replace the sensor.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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