What it means
Same as P04E1 with intermittent or erratic signal. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The crankcase ventilation hose connection sensor reports whether the PCV hose is fitted, and the control module watches for a stable signal. P04E4 sets when that signal changes erratically or drops in and out, often because vibration or harness movement interrupts the connection.
Common causes
Most likely first.
- Intermittent contact at connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Hose-connection status may change intermittently
- Crankcase ventilation warning may appear
How to diagnose it
- Review freeze-frame and scan-tool history for changes in hose connection status, noting when the intermittent fault was recorded.
- Confirm the PCV hose is secure and inspect the sensor connector for loose fit, corrosion, moisture, or damaged terminals.
- Inspect the harness routing for chafing or contact with vibrating, hot, or moving components.
- Monitor the connection signal while gently wiggling the connector and harness to reproduce any dropouts.
- Test the sensor circuit for intermittent continuity and verify sensor operation against the manufacturer's specification.
Common fixes
- Secure the connector and repair loose or corroded terminals.
- Reroute and secure harness sections that are rubbing or vibrating against other components.
- Repair damaged wiring causing an intermittent connection.
- Replace the sensor if its signal remains erratic with a sound connector and harness.
Can I keep driving?
If the PCV hose remains secure and the engine runs normally, cautious driving is generally possible while arranging repair. If the hose becomes disconnected or the engine begins running poorly, stop and correct the connection because ventilation and emissions can be affected.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.