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

What it means

The supply voltage feeding the IMRC actuator on bank 1 is below the lower limit — typically a fuse, relay, or harness fault on the supply rail.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The IMRC actuator on bank 1 moves intake manifold runners to alter airflow as engine conditions change. The control module monitors the actuator's supply feed, and P201B sets when that bank 1 supply voltage falls below the required range, preventing reliable runner control.

Common causes

Most likely first.

1. Supply fuse blown
2. Open supply wire
3. Supply relay contacts pitted

Symptoms

• Check-engine light
• Reduced engine power or sluggish acceleration
• Hesitation or uneven engine response

How to diagnose it

1. Record freeze-frame data and check whether other low-voltage or IMRC supply codes were set at the same time.
2. Inspect the bank 1 actuator supply fuse and its terminals for a blown element, heat damage, or poor contact.
3. Trace the bank 1 actuator supply wiring and connectors for an open, chafing, corrosion, or loose terminal.
4. Measure voltage at the bank 1 actuator supply while the circuit is commanded on, comparing it with the manufacturer's specification.
5. If the feed is low, check the supply relay and its control and output connections under load before replacing the actuator.

Common fixes

• Replace a blown bank 1 IMRC supply fuse after checking for a short or overload that caused it to fail.
• Repair an open or damaged bank 1 actuator supply wire or connector.
• Clean or tighten poor relay or connector terminals in the bank 1 supply path.
• Replace a relay with failed or high-resistance contacts if testing confirms the voltage drop.

Can I keep driving?

If the engine runs normally, a short gentle trip for diagnosis is generally reasonable, but reduced power or hesitation can make acceleration unpredictable. Avoid hard acceleration and repair the low supply soon because bank 1 runners may not follow commands, affecting performance and emissions.