Code Definition

P1905 — Charge air cooler pump relay shorted to positive

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Volkswagen

About P1905

P1905 is a manufacturer-specific powertrain diagnostic trouble code recorded for Volkswagen vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1905 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

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.

P1905 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This fault code is set when the engine control module (ECM) detects a short-to-positive condition in the charge air cooler pump relay circuit. The charge air cooler pump helps regulate intake air temperature by circulating coolant through the intercooler. A short-to-positive condition can cause the pump to run continuously or erratically, potentially affecting engine performance and efficiency.

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