P201BIntake Manifold Runner Control Actuator Supply Voltage Low (Bank 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P201B does not concern the control signal but the power feed of an electric flap actuator on bank 1. GM's 2025 diesel tables describe it for a swirl valve driven by a DC motor: if the supply seen by the driver falls below 6 V while the powertrain relay itself delivers more than 11 V, and this holds in 240 of 300 samples taken every 12.5 ms, a Type B fault is stored. So the voltage is lost between relay and actuator, for example at a fuse, connector or chafed wire. GM bulletin 21-NA-149 for the 2021 3.0L LM2 Duramax (Silverado, Sierra, Tahoe, Suburban, Yukon, Escalade) lists P201B among many codes caused by engine harness chafing that can blow fuses. GM's 2017–2018 diesels also include P201B in the fault group that switches swirl control off. The bank 2 version is P201C.
- What you may notice
- Malfunction indicator lamp on
- Swirl flaps no longer move, often with other electrical codes
- Likely causes
- LikelyChafed engine harness shorting or interrupting the actuator feed
- PossibleBlown fuse in the actuator supply
- PossibleHigh resistance at the supply pin of the actuator connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €10 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.