P26BB on Chevrolet
Engine Coolant Bypass Valve "C" Range/Performance
P26BB on Chevrolet vehicles indicates engine coolant bypass valve "c" range/performance. Au7o has documented this code across 1 Chevrolet model — most commonly on Silverado 1500. A generic OBD-II code indicating engine coolant bypass valve C is electrically operating but its performance (actual coolant flow/temperature response versus expected) is out of range. On some vehicles this can appear transiently during the valve break-in period and self-clear after further actuations.
Common Causes of P26BB
- •Coolant bypass valve C sticking or slow to respond
- •Debris/contamination affecting valve travel
- •Valve break-in variation (low mileage)
- •Coolant flow restriction
- •Valve wear or internal fault
- •Faulty ECM (rare)
P26BB on Chevrolet by Model
Chevrolet Silverado 1500(1 issue)
- 3.0L Duramax (LM2) engine coolant control valve failure (GM Special Coverage N252508341)2021-2022
Silverado 1500 trucks with the 3.0L LM2 Duramax inline-6 turbodiesel are prone to failure of the electronically actuated engine coolant control valve. Failure illuminates the check-engine light, can leave cooling fans running after the key is off (draining the battery), and in some cases causes the engine to run hotter than normal. A frequent root cause is corrosion/terminal damage in the coolant flow control valve actuator harness connector. GM announced Special Coverage N252508341 (September 2025) extending warranty to 15 years / 150,000 miles from in-service date for the affected valve on 2021-2022 Silverado 1500 (and 2021-2023 Tahoe/Suburban and GMC/Cadillac siblings). Owners have reported multi-month back-orders on the replacement valve (part 40009644).
Looking for P26BB on a different make?
View P26BB across all makes →Frequently Asked Questions
What does P26BB mean on Chevrolet?▼
P26BB stands for "Engine Coolant Bypass Valve "C" Range/Performance." A generic OBD-II code indicating engine coolant bypass valve C is electrically operating but its performance (actual coolant flow/temperature response versus expected) is out of range. On some vehicles this can appear transiently during the valve break-in period and self-clear after further actuations. On Chevrolet specifically, this code is documented across 1 model.
What causes P26BB on Chevrolet vehicles?▼
Common causes on Chevrolet: Coolant bypass valve C sticking or slow to respond, Debris/contamination affecting valve travel, Valve break-in variation (low mileage), Coolant flow restriction, Valve wear or internal fault. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P26BB on a Chevrolet?▼
Repair costs vary widely depending on the root cause and specific Chevrolet model.
Which Chevrolet models have P26BB documented?▼
Au7o has documented P26BB on 1 Chevrolet model: Silverado 1500.