P0401: Exhaust Gas Recirculation (EGR) Flow Insufficient
The engine computer commanded EGR flow but didn't see the expected change. The EGR passages or valve are likely clogged with carbon.
Green, yellow, red: three ways P0401 can look
The same code can be a quick fix or a reason to pull over. Match your situation to the closest example.
Keep an eye on it
Light on, no pinging, drives normally.
Schedule a repair
Pinging under load, or more frequent regens on a diesel. Get it cleaned or repaired soon.
Stop and get help
Heavy knocking, or a diesel derating. Stop working it hard; knocking can damage pistons.
Symptoms you might notice
- Pinging or knocking under load (gas)
- Usually no other symptoms
- On diesels: more soot and faster DPF loading
Common causes, cheapest first
- Carbon-clogged EGR passages or valve
- Stuck EGR valve
- Failed EGR position or pressure sensor
- Cracked vacuum line (older vehicles)
- Clogged EGR cooler (diesel)
What you can check before calling
- Listen for pinging when accelerating uphill
- On a diesel, note how often the DPF regenerates
A code points to a system, not a part. Replacing parts based on the code alone is how people spend money without fixing the problem. Testing confirms the cause first.
Generic codes (second character 0) mean the same thing on every vehicle. Some manufacturers add their own details, so check service information for your exact vehicle.
Related codes
More egr codes
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does P0401 mean?
P0401 means "Exhaust Gas Recirculation (EGR) Flow Insufficient". The engine computer commanded EGR flow but didn't see the expected change. The EGR passages or valve are likely clogged with carbon.
Can I drive with code P0401?
It depends on what the vehicle is doing. Green: Light on, no pinging, drives normally. Yellow: Pinging under load, or more frequent regens on a diesel. Get it cleaned or repaired soon. Red: Heavy knocking, or a diesel derating. Stop working it hard; knocking can damage pistons.
What causes P0401?
The most common causes are: carbon-clogged EGR passages or valve; stuck EGR valve; failed EGR position or pressure sensor.
Is P0401 a serious code?
It can be. Heavy knocking, or a diesel derating. Stop working it hard; knocking can damage pistons.
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