P26A5 on Subaru
Engine Coolant Bypass Valve "B" Range/Performance
P26A5 on Subaru vehicles indicates engine coolant bypass valve "b" range/performance. Au7o has documented this code across 2 Subaru models — most commonly on Legacy, Outback. This code means the computer determined that engine coolant bypass valve 'B' is operating outside its expected range or not responding as commanded. Coolant bypass valves regulate coolant flow through the engine to control warm-up speed and maintain a stable operating temperature. When valve 'B' underperforms, the engine may warm up slowly, run too hot or cold, or have weak cabin heat, so it should be diagnosed to protect the cooling system. Typical repair costs on Subaru range from $900 to $2,200, depending on the specific model and root cause.
Common Causes of P26A5
- •Faulty or sticking coolant bypass valve 'B'
- •Clogged or restricted coolant passages/lines
- •Damaged, corroded, or loose wiring and connectors
- •Low coolant or trapped air in the system
- •Faulty coolant temperature sensor input
- •PCM/ECM fault (rare)
P26A5 on Subaru by Model
Subaru Legacy(1 issue)
- Thermo Control Valve Failure Causing Check Engine Light, Poor Heater Performance, and Possible Overheating2021-2024
Multiple owners of 7th-generation Legacy models have reported failure of the electronically controlled thermo control valve used in the FB25 cooling system. When the valve sticks or its internal position sensor fails, the car may illuminate the check engine light, lose cabin heat, run the radiator fans excessively, and in some cases overheat or enter a reduced-power mode. Subaru issued service information and the problem is widely documented across Subaru owner communities and complaint databases for this platform.
Subaru Outback(1 issue)
- Thermo Control Valve Failure Causing Check Engine Light and Overheating Risk2020-2023
Multiple 2020-2023 Outback owners with the 2.5L FB25 engine report failure of the thermo control valve assembly, which can trigger a check engine light, disable normal coolant flow control, and in some cases lead to overheating or poor heater performance. Subaru issued a warranty extension and service communications because the valve's internal position sensor/motor can fail. Owners commonly see the problem well before 100,000 miles, often with no prior cooling-system symptoms.
Looking for P26A5 on a different make?
View P26A5 across all makes →Frequently Asked Questions
What does P26A5 mean on Subaru?▼
P26A5 stands for "Engine Coolant Bypass Valve "B" Range/Performance." This code means the computer determined that engine coolant bypass valve 'B' is operating outside its expected range or not responding as commanded. Coolant bypass valves regulate coolant flow through the engine to control warm-up speed and maintain a stable operating temperature. When valve 'B' underperforms, the engine may warm up slowly, run too hot or cold, or have weak cabin heat, so it should be diagnosed to protect the cooling system. On Subaru specifically, this code is documented across 2 models.
What causes P26A5 on Subaru vehicles?▼
Common causes on Subaru: Faulty or sticking coolant bypass valve 'B', Clogged or restricted coolant passages/lines, Damaged, corroded, or loose wiring and connectors, Low coolant or trapped air in the system, Faulty coolant temperature sensor input. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P26A5 on a Subaru?▼
Repair costs on Subaru range from $900 to $2,200, depending on the specific model and root cause.
Which Subaru models have P26A5 documented?▼
Au7o has documented P26A5 on 2 Subaru models: Legacy, Outback.