P2578
Turbocharger/Supercharger Speed Sensor A Circuit
Turbocharger / boost control
Generic OBD-II
Medium
What it means
P2578 means the engine computer sees a fault in the "A" turbocharger or supercharger speed sensor circuit. This sensor reports how fast the turbo is spinning so the ECM can control boost safely. A circuit fault usually traces to the sensor or its wiring, and the computer often limits boost until it's fixed.
Medium
Can I keep driving? The engine starts and runs, but the ECM may limit boost as a safety fallback, so expect reduced power or a possible limp mode.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced power / limited boost
- Possible limp mode under load
- No turbo speed reading in live data
Common causes
Most likely first
- Faulty turbocharger/supercharger speed sensor 'A'Likely
- Open, shorted, or chafed wiring in the sensor circuitCommon
- Corroded or loose sensor connectorCommon
- Poor ground or high-resistance connectionLess often
- Debris or oil contamination on the sensor tipLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for a turbo speed reading in live data.
- Inspect the speed-sensor connector and wiring for damage, corrosion, or heat exposure.
- Verify the reference, ground, and signal at the sensor against spec.
- Clean the sensor tip and check its mounting/air gap if applicable.
- Replace the speed sensor if wiring is good, then clear and road-test under load.
FAQ
Quick answers
Is it safe to drive with P2578?+
Short term yes, but the ECM may cap boost and cut power to protect the turbo. Avoid hard acceleration and get it diagnosed.
Can I just clear P2578?+
It returns until the sensor or its wiring is repaired. Trace the circuit first.
Related codes
Often seen with P2578
Read & clear P2578 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