P0238Powertrain
Powertrain · SAE
Turbocharger/Supercharger Boost Sensor A Circuit High
Meaning
The output voltage of boost pressure sensor A exceeds the maximum operating range threshold. The ECM interprets the signal as a short to supply voltage or an internal sensor failure.
Common causes
- Short of the signal wire to supply voltage (5 V or battery)
- Open sensor ground wire
- Failed MAP/boost sensor with output stuck high
- Damaged connector with accidental bridge between signal and supply pins
- Electromagnetic interference on the signal wire
Symptoms
- Check-engine light on
- Boost pressure reading at full scale even with engine off
- Protective power reduction (limp-home) or over-enrichment
- Possible excessive smoke from incorrect turbo mapping
- Abnormal turbo response
Severity
High: the ECM may reduce or eliminate boost for protection, causing severe performance loss.
What to do
- Measure signal voltage at the connector: near 5 V indicates short to supply or open ground
- Check sensor ground continuity
- Inspect wiring for bridging or insulation damage
- Replace the MAP/boost sensor if the circuit is intact
- Verify actual boost pressure with an external gauge