Powertrain, generic (extended)

P201B Intake Manifold Runner Control Actuator Supply Voltage Low (Bank 1)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Chafed engine harness shorting or interrupting the actuator feed
Blown fuse in the actuator supply
High resistance at the supply pin of the actuator connector

Symptoms

  • Malfunction indicator lamp on
  • Swirl flaps no longer move, often with other electrical codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€10–400
Time0.3–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

imrc actuatorimrc supply relayimrc supply fuse

Related codes

P201CP201DP2008P2009P2010

References: gsi.ext.gm.com, static.nhtsa.gov, gsi.ext.gm.com.