Code Definition

P3005 — Engine coolant heater relay 2 high output

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

About P3005

P3005 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 P3005 is stored, the module has detected a signal or supply voltage higher 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.

P3005 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

The engine control module (ECM) sets DTC P3005 when it detects that the output of Engine Coolant Heater Relay 2 is higher than expected, which typically indicates a short to battery voltage or a relay stuck closed. On many diesel Audi models an electric coolant heating element is switched through one or more high current relays to warm the coolant during cold starts, improving cabin heat and emissions. A high output fault means relay 2 is passing current when it should not, so the heating element may stay energised longer than intended. This adds unnecessary electrical load, can flatten the ba...

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