Code Definition

P1902 — Radiator fan run-on relay circuit open or shorted to ground

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

About P1902

P1902 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 P1902 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.

P1902 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 P1902 sets when the engine control module (ECM) detects an open circuit or a short to ground in the radiator fan run on relay circuit. The run on relay allows the cooling fan to keep operating for a period after the engine is switched off to carry heat away and prevent heat soak. When this control circuit is open or shorted to ground, the ECM cannot drive the relay correctly, so the after run fan may fail to operate or run inconsistently. This can allow under bonnet temperatures to climb after shutdown, and on a hot restart the coolant temperature may read higher than normal. The driver wi...

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