P004D
Turbocharger/Supercharger Boost Control B Circuit High
Turbo / boost control
Generic OBD-II
High
What it means
P004D means the engine computer detected an abnormally high voltage on the 'B' boost control circuit for the turbo or supercharger — typically a short to voltage, a wiring fault, or a failed boost control solenoid. It's an electrical fault, not a mechanical boost leak, and it usually limits power until the circuit is repaired.
High
Can I keep driving? Usually drivable, but boost may be limited and the car can enter a reduced-power limp mode until the circuit fault is fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced power or sluggish acceleration, often with limp mode
- Low or inconsistent boost pressure
- Occasional whistling or hissing under load
Common causes
Most likely first
- Short to voltage in the boost control 'B' circuit wiringLikely
- Failed boost control solenoid or actuatorCommon
- Damaged, loose, or corroded connector at the boost control componentCommon
- Open in the control circuit that pulls the signal highLess often
- Failed engine control module (ECM) — rareLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note any companion boost-control codes.
- Inspect the boost control solenoid/actuator connector and wiring for a short to voltage or damage.
- Measure the solenoid resistance and check its control and ground circuits against spec.
- Repair any shorted or chafed wiring and clean corroded connectors.
- If wiring and solenoid test good, consider the ECM last. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P004D?+
Short trips are usually fine, but power will be limited. Avoid hard acceleration or towing until the boost control circuit is repaired.
Can I just clear P004D?+
Clearing it won't help — a circuit-high fault is electrical, so it returns quickly until the wiring, connector, or solenoid is fixed.
Related codes
Often seen with P004D
Read & clear P004D yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX