What it means
Turbocharger B Boost Control Position At Low Limit: the control module has detected this fault condition. This affects turbo/supercharger boost-pressure control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Turbocharger B's boost control position feedback lets the control module monitor actuator travel while regulating boost. This code sets when B-side position reaches or remains at its low limit during boost control, pointing to a control, feedback, or boost-production problem; it does not by itself prove the vehicle has a second turbo.
Common causes
Most likely first.
- Boost-control actuator or linkage unable to reach the low limit
- Position sensor or calibration fault
- Turbocharger B boost-control wiring or connector fault
Symptoms
- Check-engine light may come on
- Reduced engine power or boost may occur
How to diagnose it
- Record freeze-frame data and compare turbo B's commanded and actual position with requested and actual boost in live data to see whether the low-limit condition coincides with a boost shortfall.
- Inspect turbo B's wiring and connector for damaged insulation, loose pins, corrosion, or poor contact.
- Check the B-side actuator and linkage for binding or inability to reach the low end of travel.
- Inspect the associated charge-air hoses and connections for leaks that could prevent the requested boost from building.
- Test B-side position feedback and actuator movement against the manufacturer's specification before replacing parts.
Common fixes
- Repair a damaged or loose turbo B connector or wiring.
- Free or repair a B-side actuator or linkage that cannot reach its commanded position.
- Repair a confirmed leak in the charge-air path associated with turbo B.
- Replace a faulty position sensor or actuator only after testing identifies the failed part.
Can I keep driving?
Drive gently and avoid towing or hard acceleration while B-side boost control is limited; the vehicle may have reduced power. Stop if power loss becomes severe, smoke is heavy, or the turbo makes unusual noises.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.