Code Definition

P3005 — Engine coolant heater relay 2 high output

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

About P3005

P3005 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 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 this code when it detects that Engine Coolant Heater Relay 2 is providing an excessively high output, which may indicate a short to battery voltage or a stuck relay. The engine coolant heater is used to pre-warm the coolant, improving cold-start performance and emissions. A malfunction can lead to unintended heater operation, increased electrical load, or component damage.

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