VOLVO
ECM-042B - Rear temperature sensor, catalytic converter. Faulty signal
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
4 modelsC30 (2007–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)
Show models by year and engine (10)
- Volvo C30 (2007–2013)2007Engine D4204T only
- Volvo C30 (2007–2013)2008–2010Engine D4204T only · Transmission MMT6, MPS6 only
- Volvo C70 (2006–2013)2008Engine D4204T only
- Volvo C70 (2006–2013)2009–2010Engine D4204T only · Transmission MMT6, MPS6 only
- Volvo S40 (2004–2013)2005–2006Engine D4204T, D4204T2 only
- Volvo S40 (2004–2013)2007Engine D4204T only
- Volvo S40 (2004–2013)2008–2010Engine D4204T only · Transmission MMT6, MPS6 only
- Volvo V50 (2004–2013)2005–2006Engine D4204T, D4204T2 only
- Volvo V50 (2004–2013)2007Engine D4204T only
- Volvo V50 (2004–2013)2008–2010Engine D4204T only · Transmission MMT6, MPS6 only
What does this fault code mean?
The engine control module (ECM) continuously compares the signal from the rear temperature sensor in the catalytic converter with a calculated value. If they do not match, the fault is set, and it is diagnosed when the ignition is switched on. The causes are poor contact in the connections, an open or shorted wiring fault, or a damaged temperature sensor.
Possible causes
- Poor contact, contact resistance or oxidation at the sensor terminals
- Open circuit or short circuit in the wiring to the temperature sensor
- Damaged temperature sensor
What you can do
- 1Switch off the ignition and check the connector to the rear temperature sensor for looseness, contact resistance and oxidation
- 2Use a multimeter to check that the signal wire from the rear sensor has no open circuit and is not shorted to ground or voltage
- 3Also use a multimeter to check that the voltage wire to the sensor has no open circuit and is not shorted to ground or voltage
- 4If you have a diagnostic tool, read the rear sensor temperature in live data while the engine warms up and check that it rises evenly
- 5If the fault remains, have a workshop with diagnostic equipment check the rear temperature sensor and replace it if needed
Symptoms you may notice1
- The check engine lamp lights or behaves abnormally
General guidance for car owners. Diagnosis on the car can point to a different cause.