P239B: Diesel Intake Air Flow B Control Motor Current Range or Performance

What it means

The motor current of the actuator on diesel intake air flow B is outside the calibrated window - typically excessive (sticky valve), or too low (worn brushes).

At a glance

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

How it works

The diesel intake air flow B control motor moves valve B to regulate intake airflow. The control module monitors motor current while commanding movement; this code sets when the current falls outside the expected range, such as when a binding valve overloads the motor or a worn motor draws too little current.

Common causes

Most likely first.

1. Intake air flow control motor worn or failing
2. Valve or linkage binding and overloading the motor
3. Motor circuit or connector fault

Symptoms

• Check-engine light on
• Reduced engine power or sluggish acceleration
• Rough idle or stalling

How to diagnose it

1. Read freeze-frame data and command the B actuator with a scan tool, if supported, while watching motor current and position response.
2. Inspect the B motor connector and wiring for loose, corroded, damaged, or overheated connections.
3. Check whether valve B and its linkage move freely with the engine off, following the manufacturer's service procedure.
4. Test the motor circuit for opens, shorts, and poor connections, and compare current draw with the manufacturer's specification.
5. If the circuit is sound, assess the motor and valve assembly for internal wear or binding that causes abnormal current.

Common fixes

• Repair loose, corroded, or damaged connections at the B control motor.
• Repair an open or shorted section of the motor wiring.
• Remove carbon or debris that is binding the B valve or linkage, if serviceable.
• Replace the worn B control motor or the faulty valve and actuator assembly.

Can I keep driving?

Reduced power, rough idle, or stalling can make driving unpredictable, so avoid heavy traffic and stop if the engine stalls or cannot accelerate safely. Continued operation with a binding valve can further strain the control motor.