Code Definition

P26A3 — Engine Coolant Bypass Valve 'A' Range/Performance

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P26A3

P26A3 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P26A3 is stored, the module has detected a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour.

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.

Because P26A3 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

P26A3 is set when the engine control module commands the engine coolant bypass valve, known on Subaru as the thermo control valve, to a given position and the resulting coolant behaviour does not match what the module expects. The valve is an electrically operated valve that redirects coolant around or through the radiator circuit so the engine reaches operating temperature quickly and then holds a tightly controlled temperature for emissions and fuel economy. The module compares commanded valve position against engine coolant temperature, radiator outlet temperature and the warm up rate acros...

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