What does fault code ECM-P2A0021 mean?

Diagnostic fault code details for ECM-P2A0021 (Volvo C30 (2007–2013), Volvo C70 (2006–2013), Volvo C70 (2006–2013)). Repair service at OBD Tuning.

VOLVO

ECM-P2A0021 - O2 Circuit Range / Performance (Bank 1, Sensor 1). General Signal Failures. Signal too low

System

Engine Control Module (ECM)

Volvo models this fault code applies to

Applies to the following models:

13 models

C30 (2007–2013), C70 (2006–2013), S40 (2004–2013), S60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V50 (2004–2013), V60 (2011–), V70 (2008–), XC60 (2009–), XC70 (2008–), XC90 (2003–)

Show models by year and engine (46)

What does this fault code mean?

The code concerns the signal from the oxygen sensor, which the engine control module (ECM) uses to assess the fuel and air mixture. It is set when the signal is too low, and the last measured value is then used.

Possible causes

Signal wire shorted to ground

What you can do

1Read the code with a diagnostic tool and check whether it is active or only stored
2Check that the signal wire to the oxygen sensor is not shorted to ground, for example from chafing or moisture
3Use a multimeter to check that the signal wire from the sensor has no contact with ground (the body) when the connector is unplugged
4With a diagnostic tool you can read the oxygen sensor signal in live data when the engine is warm and see whether it responds to the throttle
5Have a workshop calibrate the oxygen sensor, and check the sensor if the fault remains

Symptoms you may notice1

No noticeable symptoms for the driver

What the fault can affect1

The last value measured by the oxygen sensor is used

General guidance for car owners. Diagnosis on the car can point to a different cause.