What happens if I ignore an EGR code?

Ignoring an EGR code can lead to increased NOx emissions, engine knocking, poor fuel economy, and potential engine damage from detonation. It will also cause an emissions test failure.

How much does EGR repair cost?

EGR repairs range from $150 for cleaning to $400-$600 for valve replacement. EGR cooler replacement on diesel engines can cost $800-$1,500.

P0402

Exhaust Gas Recirculation Flow Excessive Detected

Moderateegr

Overview

The P0402 code indicates the PCM has detected a exhaust gas recirculation flow excessive detected fault in the exhaust gas recirculation (EGR) system. The EGR system reduces nitrogen oxide (NOx) emissions by recirculating a controlled amount of exhaust gas back into the intake manifold. An EGR malfunction can cause rough running, engine knocking, and increased emissions.

Symptoms

Engine hesitation or stumbling
Increased NOx emissions
Reduced fuel economy
Rough idle

Common Causes

Faulty PCM commanding incorrect EGR operation
Carbon buildup in EGR valve or passages
Failed EGR valve (stuck open or closed)
Faulty EGR position sensor

Diagnosis Steps

1Connect an OBD-II scanner and read all stored trouble codes and freeze frame data
2Inspect the EGR valve for carbon buildup; clean or replace as needed
3Test the EGR valve operation by applying vacuum or using the scan tool
4Check EGR passages for carbon blockage
5Test the EGR position sensor and wiring with a multimeter

Estimated Repair Cost

$150 — $600

Cost varies by vehicle, location, and repair shop. Includes parts and labor.

Commonly Affected Vehicles

Toyota TacomaVolkswagen TDI modelsRam 1500Chevrolet Silverado

Related Codes

P0406 P0405 P0404

More Egr Codes

P0400Exhaust Gas Recirculation Flow Malfunction

Moderate

P0401Exhaust Gas Recirculation Flow Insufficient Detected

Moderate

P0403Exhaust Gas Recirculation Circuit Malfunction

Moderate

P0404Exhaust Gas Recirculation Circuit Range/Performance

Moderate

P0405Exhaust Gas Recirculation Sensor "A" Circuit Low

Moderate

P0406Exhaust Gas Recirculation Sensor "A" Circuit High

Moderate

Frequently Asked Questions

Yes, EGR valves clogged with carbon can often be cleaned using throttle body or EGR cleaner. This is a cost-effective first step before considering replacement.