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DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P201B

P201BIntake Manifold Runner Control Actuator Supply Voltage Low (Bank 1)

P201B means the engine computer has detected that the supply voltage to the intake manifold runner control (IMRC) actuator on bank 1 is lower than expected. The IMRC actuator uses a small electric motor or solenoid to move a flap inside the intake manifold, and this code sets when the computer sees the voltage feed to that actuator drop below a calibrated threshold.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • A slight hesitation or stumble during light acceleration at lower engine speeds
  • Reduced engine power or sluggish throttle response in certain rpm ranges
  • Rough idle quality or an occasional misfire feeling under load
  • Poor fuel economy compared to normal driving
  • In rare cases, a noticeable loss of low-end torque because the runner flaps stay in the wrong position

Common causes, most likely first

  1. A blown fuse or corroded fuse box terminal supplying the IMRC actuator circuit
  2. Damaged, chafed, or disconnected wiring between the fuse box and the IMRC actuator
  3. High resistance in a connector terminal at the actuator or at the computer, often from water intrusion or corrosion
  4. A faulty IMRC actuator with an internally shorted or open motor winding that drags the supply voltage down
  5. A weak or failing relay that feeds the actuator circuit, if the manufacturer uses one
  6. Low system voltage from a failing battery or alternator, which can set this code as a side effect
  7. A rare internal fault in the engine control module (ECM) driver circuit for the actuator supply

How to diagnose and fix it

  1. Check for any other low-voltage or charging system codes and verify battery and charging system health first
  2. Inspect the fuse that protects the IMRC actuator supply circuit and replace it if blown, then recheck for the code
  3. Visually inspect the wiring harness and connector at the IMRC actuator for chafing, corrosion, or loose pins
  4. Measure voltage at the actuator supply terminal with the key on and compare it to battery voltage to confirm the low-voltage condition
  5. Perform a voltage drop test on the supply wire and ground circuit to locate excessive resistance
  6. Command the IMRC actuator with a scan tool and observe supply voltage and actuator movement to isolate an actuator fault
  7. If voltage is low only at the actuator and wiring checks out, replace the IMRC actuator and clear the code

Low voltage does not always mean a bad actuator

  • A weak battery or a failing alternator can cause this code because the IMRC supply voltage drops below threshold during cranking or under load, so always check charging system health before condemning the actuator.
  • Corrosion inside the connector at the IMRC actuator is a common hidden cause that a simple visual inspection may miss; wiggle-testing the harness while watching live voltage data often reveals the intermittent fault.
  • The code can set intermittently and leave no drivability symptom, leading some shops to replace the actuator unnecessarily when the real problem is a chafed wire near the intake manifold.
  • On some vehicles, the IMRC actuator shares a supply circuit with other engine components, so a fault in a seemingly unrelated device can drag the voltage down and set P201B.
  • A scan tool that can graph actuator supply voltage in real time is far more useful than a static code reader for catching this fault, because the voltage may only drop under specific engine load or temperature conditions.

Can I keep driving with P201B?

You can usually drive the vehicle with this code because the engine will default to a safe runner position, but avoid heavy acceleration and towing until the fault is repaired. If the check engine light starts flashing or you notice severe power loss, stop driving and have the vehicle inspected promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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