P0401
PPowertrainEGR Flow Insufficient
What does this code mean?
Severity : MediumP0401 means the ECU has detected insufficient exhaust gas recirculation flow. When it opens the EGR valve, it expects a change in airflow or intake pressure that does not happen as much as it should. This usually points to a clogged EGR valve or blocked EGR passages.
Symptoms
- Check engine light on.
- Pinging or knocking under load on petrol engines.
- Slight loss of power or hesitation.
- Possible emissions test failure for NOx.
- Sometimes no noticeable drivability symptom.
Possible causes
- EGR valve clogged with carbon or stuck closed.
- Blocked EGR passages, intake ports or EGR cooler.
- Faulty control solenoid or leaking vacuum hose.
- Faulty EGR position or pressure sensor.
- Corroded connector or damaged wiring.
Diagnosis and repair
- Check the EGR valve connector, wiring and hoses.
- Command the valve with a scan tool and watch its response in live data.
- Remove the valve to inspect the valve and passages for carbon build-up.
- Clean the EGR valve and passages, or replace the valve if needed.
- Clear the code and road test under varied conditions.
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Code
P0401
Category
Powertrain
Prefix
P
Standard
OBD-II / SAE J2012