VOLVO
ECM-P029921 - Turbocharger/Supercharger A Underboost Condition. General Signal Failures. Signal too low
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
7 modelsS60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V60 (2011–), V70 (2008–), XC60 (2009–)
Show models by year and engine (20)
- Volvo S60 (2011–)2011Engine B4164T, B4164T3, B4204T6, B4204T7 only
- Volvo S60 (2011–)2012–2014Engine B4164T, B4164T2, B4164T3, B4204T7 only
- Volvo S60 (2011–)2015Engine B4164T, B4164T2, B4164T3 only
- Volvo S80 (2007–)2010Engine B4204T6 only
- Volvo S80 (2007–)2011Engine B4164T, B4204T6, B4204T7 only
- Volvo S80 (2007–)2012–2014Engine B4164T, B4164T2, B4204T6, B4204T7 only
- Volvo S80 (2007–)2015Engine B4164T only
- Volvo V40 (2013–)2013Engine B4164T, B4164T3 only
- Volvo V40 (2013–)2014–2015Engine B4164T, B4164T3, B4164T4 only
- Volvo V40 Cross Country (2013–)2013–2015Engine B4164T only
- Volvo V60 (2011–)2011Engine B4164T, B4164T3, B4204T6, B4204T7 only
- Volvo V60 (2011–)2012–2014Engine B4164T, B4164T2, B4164T3, B4204T7 only
- Volvo V60 (2011–)2015Engine B4164T, B4164T2, B4164T3 only
- Volvo V70 (2008–)2010Engine B4204T6 only
- Volvo V70 (2008–)2011Engine B4164T, B4204T6, B4204T7 only
- Volvo V70 (2008–)2012–2014Engine B4164T, B4164T2, B4204T7 only
- Volvo V70 (2008–)2015Engine B4164T, B4164T2 only
- Volvo XC60 (2009–)2010Engine B4204T6 only
- Volvo XC60 (2009–)2011–2012Engine B4204T6, B4204T7 only
- Volvo XC60 (2009–)2013–2015Engine B4204T7 only
What does this fault code mean?
The code concerns a signal fault in the boost pressure control. The ECM compares the boost pressure measured by the sensor with the target value and stores the code when the pressure is below the target. The fault can only be detected when engine speed and load are high enough. It may be caused by the turbo control valve, hoses in the system or the sensor.
Possible causes
- Damaged turbo control valve, or incorrect setting on the wastegate valve's pressure actuator
- Damaged or sticking wastegate valve, or a damaged pressure actuator for it
- Hoses between the wastegate valve's pressure actuator and the turbo control valve that are loose, clogged or damaged
- Hoses between the turbo control valve and the charge air pipe that are clogged or damaged
- Damaged outside temperature sensor
- Damaged boost pressure sensor (TMAP)
What you can do
- 1Read and note the fault code, clear it and test drive to see whether it returns
- 2Check the hoses between the wastegate valve's pressure actuator, the turbo control valve and the charge air pipe for looseness, blockage and damage
- 3Check that the wastegate valve and its pressure actuator work and are not sticking
- 4If you have a diagnostic tool: read the boost pressure in live data while driving and check that it follows the throttle
- 5Check the connector to the boost pressure sensor for contact resistance and oxidation
- 6With the ignition off and the connector disconnected, use a multimeter to check that the signal wire to the boost pressure sensor is not short-circuited to ground
Symptoms you may notice1
- The car lacks power
General guidance for car owners. Diagnosis on the car can point to a different cause.