Code Definition

P1904 — Engine coolant hydraulic blower motor solenoid open or shorted to ground

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

About P1904

P1904 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 P1904 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit; a short-circuit (voltage pulled to ground or to supply) in the monitored circuit; and 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.

P1904 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 triggered when the engine control module (ECM) detects an open circuit or a short-to-ground condition in the engine coolant hydraulic blower motor solenoid circuit. This solenoid controls the operation of a hydraulic blower motor that assists in engine cooling. A failure in this circuit may cause improper blower operation, potentially leading to cooling inefficiencies or overheating.

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