Turbocharger/Supercharger Boost Control 'A' Circuit High
Your turbocharger boost pressure control circuit is reading higher than it should, like a pressure gauge stuck on the high end. The ECU thinks the boost control solenoid or wiring is malfunctioning and allowing too much boost pressure signal.
The ECM monitors the boost control solenoid circuit voltage, which should fluctuate within a normal operating range as the solenoid regulates turbo boost pressure. When the voltage or signal remains abnormally high, it indicates a stuck-open solenoid, wiring short, or control module malfunction. The ECU cannot properly regulate boost pressure in this state.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Boost Control Solenoid Voltage | 0.5–4.5 volts (PWM cycling) | Greater than expected maximum, stuck high |
| Boost Pressure Signal | 0–1.0 bar above atmospheric at idle | Excessive or uncontrolled boost signal detected |
Code P0048 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0048 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.