P0238 — Turbocharger/Supercharger Boost Sensor A Circuit High
Moderate severityWhat it means
P0238 is stored when the engine control unit sees a fault involving the turbocharger/supercharger boost system. The boost system forces extra air into the engine for more power; the control unit commands a wastegate or vane position and watches the boost pressure that results. A “high” reading means the signal is pinned near the top of its range — often an open circuit, a lost ground, or a short to voltage.
Common symptoms
- The live reading sits abnormally high or maxed out
- Loss of power or slow acceleration
- Limp mode under load
- Whistling or a boost-related noise
Likely causes
- Open signal or ground wire
- Signal wire shorted to a voltage supply
- A charge-air (boost) leak or split hose
- A sticking wastegate, VNT mechanism or boost-control valve
What to check first
- Check for an open circuit or missing ground at the sensor connector
- Pressure-test the charge-air pipes for leaks
- Compare commanded vs actual boost and check wastegate/VNT movement
Can you keep driving?
Often drivable with reduced power, but a stuck wastegate can over-stress the turbo — diagnose soon.
Frequently asked questions
What is the most common cause of P0238?
The most likely cause is: Open signal or ground wire. Several other faults can set P0238 as well, so confirm the real cause with live data and the checks above before replacing any parts.
Can I just clear P0238 and keep driving?
Clearing P0238 with an OBD2 scanner turns the warning light off, but if the underlying fault has not been repaired the code will usually come back within a few drive cycles. Fix the cause first, then clear the code to confirm the repair worked.
How serious is P0238?
P0238 is a moderate-severity code. The car is often still drivable, but have it diagnosed soon — the underlying problem can get worse and it may fail an emissions test.
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