Code Definition

P1900 — Radiator fan speed 2 circuit open or shorted to ground

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

About P1900

P1900 is a manufacturer-specific powertrain diagnostic trouble code recorded for Audi vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1900 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit; and 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.

P1900 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

DTC P1900 sets when the engine control module (ECM), often working through the radiator fan control module, detects an open circuit or a short to ground in the radiator fan speed 2 control circuit. Modern Audi cooling fans are electronically controlled and run at several speeds, with speed 2 being a higher speed stage used as coolant temperature climbs or when the air conditioning places extra load on the system. When the control circuit for that stage is open or shorted to ground, the ECM cannot command the higher fan speed reliably. This can lead to poor cooling at idle or in slow traffic, r...

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