What it means
The signal from the turbocharger or supercharger inlet pressure sensor B is intermittent or erratic.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Turbocharger inlet pressure sensor B reports inlet pressure to the control module. P2378 sets when its signal drops out or changes erratically rather than remaining consistent with operating conditions, often because a connector or wire loses contact intermittently.
Common causes
Most likely first.
- Intermittent contact at connector or terminal
- Harness chafed or pinched
- Connector with intermittent contact under vibration
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
How to diagnose it
- Review freeze-frame data and scan history for conditions when sensor B's signal dropped out, then watch its live reading for sudden jumps or gaps.
- Inspect sensor B's connector and harness for loose terminals, corrosion, chafing, pinching, or vibration-related movement.
- With the vehicle stationary and following the manufacturer's procedure, move the harness gently while monitoring sensor B data for a dropout.
- Check sensor B's signal, supply, and ground connections for intermittent opens or poor terminal contact.
- If the circuit remains stable, inspect the pressure port or reference hose and test sensor B for intermittent failure to the manufacturer's procedure.
Common fixes
- Secure a loose sensor B connector and restore proper terminal tension.
- Repair a chafed or pinched section of sensor B wiring.
- Clean corrosion and repair damaged connector pins or seals.
- Replace sensor B if its output remains erratic with a verified circuit and clear pressure path.
Can I keep driving?
Because the fault can cause sudden power changes, avoid high-speed driving and heavy loads if the engine hesitates or enters reduced-power operation. Stop if power loss makes the vehicle unsafe or smoke is heavy.
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.