VOLVO
ECM-259B - Front heated oxygen sensor (HO2S), bank 2. Signal missing
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsS80 (1999–2006), XC90 (2003–)
Show models by year and engine (2)
What does this fault code mean?
The engine control module (ECM) has registered an open circuit in the signal wire from the part of the oxygen sensor on bank 2 that measures oxygen content in the exhaust. The signal is therefore missing in the control module.
Possible causes
- Contact resistance or oxidation on the signal wire
- Break in the signal wire
- Damaged front oxygen sensor on bank 2
What you can do
- 1Read the code, clear it and road test the car to see whether it returns
- 2Check that the connector at the lambda sensor is fully engaged and clean, with no oxide. Do not use rust solvent spray or grease
- 3Use a multimeter to check that the signal wire runs unbroken from the sensor to the control module
- 4Look for chafing and breaks in the signal wire, especially near the exhaust system
- 5If the connectors and wiring are intact the sensor may be damaged; have a workshop check it or replace it
Symptoms you may notice1
- Malfunction indicator lamp (MIL) on
General guidance for car owners. Diagnosis on the car can point to a different cause.