Code Definition

P0402 — Exhaust Gas Recirculation Flow Excessive Detected

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0402

P0402 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0402 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0402 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The ECM/PCM sets this code when it detects that the actual exhaust gas recirculation (EGR) flow is higher than the expected value. Excessive EGR flow can cause rough idling, hesitation, or stalling due to an overly rich air-fuel mixture. This issue may result from a stuck-open EGR valve, sensor faults, or exhaust pressure abnormalities.

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