Complete diagnostic information for error code P0404
Manufacturer-Specific Variations
This code (P0404) may have different meanings or additional parameters depending on your vehicle's make, model, and year. Always verify with your vehicle's service manual or a qualified technician before attempting repairs.
P0404
Powertrain CodeExhaust Gas Recirculation (EGR), Circuit Implausible Signal
Description
Exhaust gas recirculation implausible signal
Common Symptoms
- Check Engine Light with EGR implausible signal detected
- EGR position sensor signal accuracy problems
- Inconsistent or erratic EGR valve position readings
- Emission control system signal processing errors
- EGR system operating with incorrect position information
- Failed diagnostic tests due to signal plausibility issues
Possible Causes
- Faulty EGR position sensor
- Intermittent electrical connections
- Sensor calibration problems
- Signal interference in EGR circuit
- EGR valve mechanical issues affecting position sensing
- Engine control module signal processing errors
Diagnosis Steps
- Test EGR position sensor signal pattern
- Check for intermittent electrical connections
- Verify sensor calibration and mounting
- Monitor for signal interference in EGR circuit
- Test EGR valve mechanical operation
- Check engine control module signal processing
Repair Solutions
- Replace faulty EGR position sensor
- Repair intermittent electrical connections
- Recalibrate or properly mount sensor
- Shield EGR circuit from interference
- Address EGR valve mechanical issues
- Reset EGR system signal processing
Prevention Tips
- Regular sensor signal monitoring
- Secure electrical connections
- Address signal issues promptly
Working with ECU firmware? Remove DTCs directly from firmware files
Our free Firmware DTC Remover detects and removes hardcoded fault codes directly from ECU firmware files — no software needed. Supports BMW/MINI (EDC16, EDC17, MEVD17) and VAG Group (EDC17). Free: 3 removals/day.