P0404 - Exhaust Gas Recirculation (EGR) Control Circuit Range/Performance
Last updated:
System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0404 is a rationality fault code indicating that the EGR (Exhaust Gas Recirculation) valve position sensor signal is not within a predefined range or matches the ECU's commanded position. This differs from open or short circuit codes as it focuses on the performance and movement of the valve. The ECU monitors the EGR valve via a feedback potentiometer or a Hall effect sensor. If the feedback voltage deviates from the target duty cycle (e.g., the valve is sticking due to carbon buildup or the motor is weakening), the ECU sets P0404. Since EGR is used to lower combustion temperatures and reduce NOx emissions, this fault will often trigger a fail-safe mode to protect the engine.
Possible Causes
Carbon buildup (soot) causing the valve to stick or move sluggishly.
Faulty EGR valve assembly (internal motor failure or worn potentiometer).
Wiring issues (corroded connectors or high resistance in the signal wire).
ECU software issues or loss of basic adaptation settings.
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
Do you also have
other fault codes?
See how P0404 connects with your other fault codes. Our advanced analysis tool identifies causal relationships and root causes directly.