VOLVO
ECM-243C - Front heated oxygen sensor (HO2S), bank 1 heating. Signal too high
System
Engine Control Module (ECM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
Applies to the following models:
5 modelsS60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)
Show models by year and engine (12)
- Volvo S60 (2001–2009)2006Engine B5204T5, B5244T4, B5244T5, B5254T2, B5254T4 only
- Volvo S60 (2001–2009)2007Engine B5204T5, B5244T5, B5254T2, B5254T4 only
- Volvo S60 (2001–2009)2008–2009Engine B5204T5, B5244T5, B5254T2 only
- Volvo S80 (1999–2006)2006Engine B5204T5, B5254T2, B6294S2, B6294T only
- Volvo V70 (2000–2008)2006–2007Engine B5204T5, B5244T5, B5254T2, B5254T4 only
- Volvo V70 (2000–2008)2008Engine B5254T2 only
- Volvo V70 XC / XC70 (2001–2007)2006Engine B5244T4, B5254T2 only
- Volvo V70 XC / XC70 (2001–2007)2007Engine B5254T2 only
- Volvo XC90 (2003–)2006Engine B5254T2, B6294T only
- Volvo XC90 (2003–)2007–2012Engine B5254T2 only
- Volvo XC90 (2003–)2013–2014Engine B5254T9 only
- Volvo XC90 (2003–)2015
What does this fault code mean?
The engine control module (ECM) checks the heater circuit of the front oxygen sensor. It measures the current in the circuit and converts it to a temperature. If the resistance is unreasonably high, giving too low a temperature, the module treats this as a fault and sets the code.
Possible causes
- Contact resistance and oxidation at the connections
- Damaged front heated oxygen sensor
What you can do
- 1Read the code, clear it and road test to see whether it returns
- 2Check the oxygen sensor connector for oxidation and loose connections. Do not use rust solvent spray or grease on the connector
- 3If you take readings, do it from the cable side of the connector so you do not damage it or create a future loose contact
- 4With a diagnostic tool, check the oxygen sensor temperature in live data on a warm engine. A value that stays low points to the connector or sensor
- 5If the connector is clean and the wiring intact, have a workshop with diagnostic equipment check the oxygen sensor and replace it if needed
Symptoms you may notice1
- The malfunction indicator light (MIL) is on
General guidance for car owners. Diagnosis on the car can point to a different cause.