VOLVO
ECM-0138 - Rear heated oxygen sensor (HO2S), bank 1.Faulty signal
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:
3 modelsC30 (2007–2013), S40 (2004–2013), V50 (2004–2013)
Show models by year and engine (13)
- Volvo C30 (2007–2013)2007–2009Engine B4184S11, B4184S8, B4204S3 only
- Volvo C30 (2007–2013)2010Engine B4184S11, B4184S8, B4204S3, B4204S4 only
- Volvo C30 (2007–2013)2011–2013Engine B4204S3, B4204S4 only
- Volvo S40 (2004–2013)2005Engine B4184S11 only
- Volvo S40 (2004–2013)2006Engine B4184S11, B4184S8 only
- Volvo S40 (2004–2013)2007–2009Engine B4184S11, B4184S8, B4204S3 only
- Volvo S40 (2004–2013)2010Engine B4184S11, B4184S8, B4204S3, B4204S4 only
- Volvo S40 (2004–2013)2011–2012Engine B4204S3, B4204S4 only
- Volvo V50 (2004–2013)2005Engine B4184S11 only
- Volvo V50 (2004–2013)2006Engine B4184S11, B4184S8 only
- Volvo V50 (2004–2013)2007–2009Engine B4184S11, B4184S8, B4204S3 only
- Volvo V50 (2004–2013)2010Engine B4184S11, B4184S8, B4204S3, B4204S4 only
- Volvo V50 (2004–2013)2011–2012Engine B4204S3, B4204S4 only
What does this fault code mean?
The engine control module has registered that the voltage from the rear lambda sensor on bank 1 has stayed above a set value for a set time, and treats this as a fault. The rear sensor, located after the catalytic converter, sends a signal to the control module, and the fault concerns that signal. It is usually caused by a signal wire shorted to voltage or by a damaged sensor.
Possible causes
- Signal wire shorted to supply voltage
- Damaged rear lambda sensor, bank 1
What you can do
- 1Read, clear the code and road test to see whether it returns
- 2Check that the connector at the rear lambda sensor is fully engaged and free from corrosion
- 3Follow the cable from the sensor and look for chafing, pinched sections and places where the insulation has melted
- 4With the ignition on and the connector unplugged, use a multimeter to check that the signal wire has no voltage. Voltage there means the wire is shorted to supply
- 5If you have a diagnostic tool, check in live data whether the rear sensor value stays constantly high even when the engine is warm and the throttle is released
- 6If the fault returns, have a workshop with diagnostic equipment check the wiring before the sensor is replaced
Symptoms you may notice1
- Malfunction indicator lamp (MIL) lit
General guidance for car owners. Diagnosis on the car can point to a different cause.