Code Definition

P2004 — Air Flow Sensor Volume Signal Out Of Range

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

About P2004

P2004 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Mercedes-Benz vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P2004 is stored, the module has detected a signal or supply voltage lower than the expected operating range; a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour; 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 P2004 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

This fault code indicates that the engine control module (ECM) has detected an abnormal signal from the mass airflow (MAF) sensor. The MAF sensor measures the volume and density of incoming air to calculate fuel delivery and optimise engine performance. If the sensor signal is outside the expected range, the ECM logs this fault, which can lead to drivability issues such as poor acceleration or rough idle.

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