P0240 Turbo and boost pressure: reading or operation not right ("B")

By: Diagno editorial team · Updated: 2026-10-15

P0240 means: Turbo and boost pressure: reading or operation not right ("B"). The turbo pushes extra air into the engine. Drive gently and have the car checked soon. The most common repair costs about €700–1400 in Estonia, depending on make and model. The most common cause: leaking boost hose or intercooler.

What it means

The turbo pushes extra air into the engine. The computer found the boost pressure wrong or the turbo control not working. The car often goes into limp mode. There is a signal, but the reading or operation isn't plausible. The cause may be the part itself or a real mechanical fault.

What you may notice

• Much less power (limp mode)
• Turbo whistling or hissing
• Black smoke
• Engine light on

What could be wrong

1. 1Leaking boost hose or intercooler · Turbo repair or replacement €700–1400
2. 2Turbo actuator (VNT or wastegate) stuck · Turbo repair or replacement €700–1400
3. 3Boost pressure sensor reading wrong · Alternator replacement €350–650
4. 4Control solenoid or its vacuum hose · Vacuum hose or actuator replacement €60–120
5. 5Worn turbo · Turbo repair or replacement €700–1400

Repair difficulty: Hard

What you can check yourself

Check the boost hoses, especially the joints and around the intercooler. An oily hose points to a leak. Best left to a workshop. It needs a diagnostic tool and experience.

How we fix it

1. We measure boost pressure on a test drive
2. We pressure-test the boost hoses
3. We check the actuator movement and solenoid
4. We replace the hose or sensor, or repair the turbo

Standard SAE description: Turbocharger Boost Sensor B Circuit Range/Performance