VOLVO
ECM-0140 - Rear heated oxygen sensor (HO2S), bank 1. Signal missing
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
3 modelsC30 (2007–2013), S40 (2004–2013), V50 (2004–2013)
What does this fault code mean?
The engine control module registers that the signal from the rear lambda sensor on bank 1 is missing and treats this as a fault. With no signal, the control module cannot read the rear sensor's measurement. The cause is most often an open circuit or a short in the signal wire, but a damaged sensor or control module can also cause it.
Possible causes
- Open circuit in the signal wire
- Signal wire shorted to ground
- Signal wire shorted to supply voltage
- Signal wire shorted to reference voltage
- Damaged rear lambda sensor
- Damaged control module
What you can do
- 1Read, note and clear the code, then road test
- 2Check that the connectors at the rear lambda sensor are fully engaged and not oxidized
- 3With the connector unplugged, use a multimeter to check that the signal wire has no connection to ground (the body)
- 4Follow the signal wire from the sensor and look for breaks or chafing, especially near the exhaust pipe
- 5If you have a diagnostic tool, read the rear sensor value in live data. If the value is missing entirely or never changes, the signal is gone
- 6If the fault returns, have a workshop with diagnostic equipment check the control module and decide whether the sensor needs replacing
Symptoms you may notice1
- Malfunction indicator lamp (MIL) lit
General guidance for car owners. Diagnosis on the car can point to a different cause.