Code Definition

P1256 — Engine coolant temperature sensor open circuit or shorted to positive

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

About P1256

P1256 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 P1256 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 sensor-related fault — the reported value from the named sensor is out of spec.

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.

P1256 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 coolant temperature sensor is a negative temperature coefficient thermistor mounted in the coolant flange, fed with a 5V reference through a pull up resistor inside the Engine Control Module. The module reads the resulting voltage on the signal wire, so a cold engine gives a high signal voltage and a hot engine a low one. DTC P1256 is stored when the module finds the coolant temperature circuit either open or shorted to positive, two conditions grouped under one code because both drive the signal to the top of its range and are read as an implausibly cold engine. An open circuit is ...

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