OBD2 codes.

Exhaust Gas Recirculation Flow Insufficient Detected

The EGR valve sends part of the exhaust gas back into the intake to lower combustion temperature and reduce nitrogen oxides (NOx). This code means that when the engine computer opens the EGR, less gas flows than expected.

What the car has detected

With EGR switched on, the engine computer has measured recirculated gas flow below the calibrated value (it works this out, for example, from how much the air measured by the MAF sensor drops).

You can usually drive, but the engine emits more NOx, may fail the inspection and, if the cause is carbon build-up, the problem tends to get worse. Get it checked soon.

Symptoms

• Engine warning light on
• Often no change when driving
• Knocking or pinking when accelerating on some petrol engines
• Failing the emissions test

Possible causes

• EGR valve or passages blocked with carbon
• EGR valve stuck closed
• Faulty EGR vacuum line or control valve
• On some diesels, a clogged EGR filter
• Air leaks between the turbo and the intake manifold
• Faulty mass air flow sensor

Checks for the garage

• Check there are no other codes and that the air filter isn't clogged
• Look for leaks in the intake and vacuum lines
• Check the mass air flow sensor, which can also set the code
• Move the EGR valve with diagnostics (from almost closed to almost open) and see whether it responds and the air flow changes
• Check whether the valve and passages are blocked with carbon

Next step

Have the EGR valve and its passages checked for carbon blockage, and the intake leaks and MAF sensor checked.

Go to a garage if the code comes back: cleaning or replacing the EGR usually means removing parts and using diagnostics to check it works.

Original sources · Date indicated: 2026-10-12