P003B: Turbocharger/Supercharger Boost Control B Position Exceeded Learning Limit

What it means

The control module detected that the position of turbocharger or supercharger boost control B exceeded its learned limit.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

Boost Control B is the second designated boost-control mechanism or position channel monitored by the vehicle's control module. P003B sets when its position exceeds the learned limit, potentially because the B actuator sticks or fails, its linkage binds, or the mechanism or wiring is damaged.

Common causes

Most likely first.

1. Boost control B actuator sticking or failing
2. Actuator linkage binding or out of adjustment
3. Damaged wiring or connector
4. Boost control mechanism worn or obstructed

Symptoms

• Check engine light on
• Reduced engine performance

How to diagnose it

1. Record freeze-frame data and compare commanded and actual Boost Control B position readings with a scan tool to confirm when the B position exceeds its learned limit.
2. Inspect the Boost Control B actuator, linkage, and mechanism for obstruction, binding, wear, or incorrect adjustment.
3. Check the B actuator wiring and connector for damaged insulation, corrosion, loose pins, or poor contact.
4. Use the manufacturer's procedure to command Boost Control B through its range and watch for sticking or position readings that do not follow the command.
5. Test the B actuator and position feedback against the manufacturer's specification to separate an electrical fault from a mechanical one.

Common fixes

• Remove an obstruction or correct binding in the Boost Control B mechanism.
• Repair damaged Boost Control B wiring or connector contacts.
• Adjust binding or out-of-position B linkage as specified by the manufacturer.
• Replace a Boost Control B actuator or mechanism that fails testing.

Can I keep driving?

Reduced power or limp mode may make acceleration unpredictable, so avoid hard acceleration, towing, and quick passing. If the vehicle cannot maintain a safe speed or develops abnormal engine behavior, stop in a safe place and arrange assistance.