VOLVO
ECM-220B - Rear heated oxygen sensor (HO2S). Signal too low
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
7 modelsC30 (2007–2013), C70 (2006–2013), S40 (2004–2013), S60 (2001–2009), S80 (1999–2006), V50 (2004–2013), V70 (2000–2008)
Show models by year and engine (11)
- Volvo C30 (2007–2013)2007–2011Engine B5244S4 only
- Volvo C70 (2006–2013)2006All engines except: B5254T3
- Volvo C70 (2006–2013)2007–2010Engine B5244S4, B5244S5 only
- Volvo C70 (2006–2013)2011Engine B5244S4 only
- Volvo S40 (2004–2013)2005–2010Engine B5244S4, B5244S5, B5244S7 only
- Volvo S60 (2001–2009)2005–2006Engine B5244S, B5244S2, B5244S6 only
- Volvo S60 (2001–2009)2007–2009Engine B5244S, B5244S2 only
- Volvo S80 (1999–2006)2005–2006Engine B5244S, B5244S2 only
- Volvo V50 (2004–2013)2005–2010Engine B5244S4, B5244S5, B5244S7 only
- Volvo V70 (2000–2008)2005–2006Engine B5244S, B5244S2, B5244S6 only
- Volvo V70 (2000–2008)2007–2008Engine B5244S, B5244S2 only
What does this fault code mean?
The engine control module continuously monitors the voltage from the rear oxygen sensor and treats it as a fault when the voltage is outside the expected range, here too low. The fault can lie in the signal wire, in the connectors or in the sensor.
Possible causes
- Signal wire shorted to ground
- Open circuit in the signal wire
- Contact resistance and oxidation in the connections
- Damaged rear oxygen sensor
What you can do
- 1Have a diagnostic tool? Read the fault status after the engine has idled for a while; if the fault is still present it is permanent
- 2Check the connector on the rear oxygen sensor for contact resistance and oxidation
- 3Inspect the wiring for chafing, pinching and breaks
- 4Use a multimeter to check that the signal wire is not shorted to ground or voltage
- 5If the fault remains, have a workshop try a new rear oxygen sensor
Symptoms you may notice1
- The malfunction indicator lamp (MIL) comes on
What the fault can affect1
- Control using the rear oxygen sensor is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.