P0401

Exhaust Gas Recirculation Flow Insufficient

Symptoms

• •Check engine light
• •Pinging/knock
• •Rough idle

Likely causes

• •Clogged EGR passages
• •Faulty EGR valve
• •Bad EGR sensor

Can I drive?

Plan a workshop visit.

Estimated repair cost (Malaysia)

RM200–RM800 (approximate)

Diagnostic guide (for mechanics)

Work through these in order — cheapest and safest checks first, before replacing expensive parts.

1. 1. Inspect EGR passages for carbon

   Insufficient flow is usually clogged passages or a stuck valve, common on older engines.

   Test: Remove and inspect the EGR valve and ports.

   Expected: Passages clear, valve moves freely.

2. 2. Test EGR valve operation

   Command the valve and confirm it opens/closes.

   Test: Bi-directional scan command (if supported) or manual actuation.

   Expected: Valve responds; flow changes.

3. 3. Check the DPFE / EGR sensor

   A faulty flow sensor can report low flow falsely.

   Test: Live data EGR position/flow sensor.

   Expected: Plausible, responsive reading.

Tools: OBD-II scan tool · Carbon cleaner · Hand tools

When to escalate: Clean first; replace valve or sensor only after cleaning fails to restore flow.

This is general information, not a diagnosis. AutoMalaya OBD helps explain your car’s actual scan data; a qualified mechanic may still need to inspect the vehicle.

Related fault codes

See sample report