Code Definition

P0405 — Exhaust Gas Recirculation Sensor A Circuit Low

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

About P0405

P0405 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 P0405 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

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 P0405 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 signal voltage from the EGR position sensor (Sensor A) is lower than the expected range. This typically indicates a short to ground, a faulty sensor, or wiring issues. The EGR position sensor monitors the valve's position to ensure proper exhaust gas recirculation, which is critical for reducing NOx emissions.

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