P0238Turbocharger/Supercharger Boost Sensor A Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Boost sensor A measures the absolute pressure between charge air cooler and throttle – GM calls it TIAP, Ford TIP – usually combined with an intake air temperature sensor; its voltage rises with pressure. With the ignition on and the engine stopped it must read the same as manifold and barometric pressure. P0238 means the signal voltage is above its upper limit: GM above 86 % of 5 V (about 372 kPa) for roughly 4 s with the warning light in the first trip, Ford above 4.88 V for 5 s, Saab's 1.6 turbo above 4.8 V. Causes are a signal shorted to 5 V or 12 V, an open sensor ground or – on GM modules with a pull-up input – an open signal wire. If several high codes appear at once, check the shared ground. With a sensor fault boost control is switched off and only the base boost of the wastegate spring remains, with a clear loss of power.
- What you may notice
- Check engine light on
- Clear loss of power, only base boost
- Boost reading implausible in a scan tool
- Likely causes
- LikelySensor ground open, or signal wire open on a pulled-up input
- PossibleSignal shorted to 5 V or 12 V
- PossibleSensor faulty internally
- PossibleConnector corrosion or moisture at the ground
- RareEngine module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.