P201B code meaning
Intake Manifold Runner Control Actuator Supply Voltage Low (Bank 1)
Powertrain system Generic code P20xx codes Check engine light
What P201B means
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.
P201B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P201B
- Malfunction indicator lamp on
- Swirl flaps no longer move, often with other electrical codes
Common causes of P201B
- Most 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
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Imrc actuatorImrc supply relayImrc supply fuse
What each part of P201B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 1B | The exact fault in that area. |
What to do next
- Note P201B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P201B
What does P201B mean?
P201B means "Intake Manifold Runner Control Actuator Supply Voltage Low (Bank 1)". P201B does not concern the control signal but the power feed of an electric flap actuator on bank 1. It is a generic code, so it means the same on every make.
Is it safe to drive with P201B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P201B fail an emissions test?
Yes, it can. P201B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P201B to fix?
Difficulty: medium. A typical repair takes 0.3 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P201B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.