P26A3: Engine Coolant Bypass Valve A Range/Performance — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
The coolant bypass valve A does not meet the expected operating performance. This alone does not prove a particular failed part. Manufacturer bulletins describe causes only for specified RAM and Subaru configurations.
Affected system: Powertrain
Symptoms
- A check-engine warning is documented on affected RAM vehicles; Subaru service reports also mention associated codes.
- The DTC alone does not establish a specific driving or temperature symptom.
Possible causes
- On a restricted RAM 1500 build range, Stellantis identified a cracked coolant-valve gear (TSB 07-009-23); a different range had coolant contamination (TSB 07-007-24).
- Some Subaru thermo-valve systems may disturb a shared sensor reference when the valve shorts internally; not a universal diagnosis.
What to check
- Record VIN, engine, all stored codes and freeze-frame.
- Use the exact manufacturer's method to evaluate valve commands, response and cooling operation.
- Apply RAM/Subaru bulletin findings only when the vehicle and build/wiring are eligible.
Also written as: P26A3-00, P26A300 (some scan tools add the fault-type byte, e.g. -00).