Hello to All,
I have Volvo S 70 GLT, 243,000 miles. which recently got me trouble codes:
1) ECM-261A Long-term fuel trim, bank 1 - upper limit
2) ECM-280A Front heated oxygen sensor (HO2S), bank 1- signal missing

I already replaced front oxygen sensor (Bosch), cleared all codes with VIDA, but check engine light and trouble codes are coming back after a short ride. Engine hesitates, idles rough, black smoke out of exhaust, and bad milage.
I did some more VIDA diagnostics and below I have some data.

First attachment is a picture of the life data on oxygen sensors, with ignition on (engine off).
ECM-Oxygen front sensor is reading 0.99 V
ECM-Oxygen rear sensor is reading 0.45 V



Second is a short movie showing same data with engine on, and occasional acceleration (RPM increase).

ECM-Oxygen front sensor is reading from 0 to about 3.7 V. The cycle is constantly repeating from 0 V to 3.7 again and again. (Please see attachment).
ECM-Oxygen rear sensor is reading 0.46 V

Should I replace rear oxygen sensor too? (values on it during ignition on (engine off) and idle and ocasssional acceleration is not much different?
Is the front oxygen sensor (just replaced) broken?

Any help or suggestions on how to fix this problem?

Thank you in advance.

 

1/2 - You have Vida. If you click on the code you get the screens below - have you tried Volvos suggestions as to a possible source? (highlighted in the green boxes)
3. OK
4. If you have an air leak between the turbo and the throttle plate - you will get those symptoms - check your intercooler hoses. Black smoke bad mileage are because the air mass meter measures air going into the turbo, injectors deliver that amount of fuel - but the compressed air has leaked out before it gets to the combustion chamber - and is way too rich.
5. Measuring O2 sensor voltage with engine off is not a valid test for anything. O2 sensors don't output valid readings until they are ~700 degrees - and the ECU ignores the signals for X time after the car is started to allow them to heat up.
6. I have never seen an O2 sensor put out more than 1.2 volts - so I'm not sure what you are reading. Simply use a voltmeter and see what you get.
7. The rear sensor in theory, if the catalytic converter is still working, should read close to 0 volts. The reading might be elevated because the mixture is too rich (due to an air leak in the intake system, that may only leak under boost)
8. No. The rear sensor even if not working has no control over your problems. It simply reports how much O2 is left after the catalytic converter uses it to convert co2 and o2 into co and hc and o2 into h2o. If the sensor is bad - you will get a code. Then MAYBE it should be replaced.

Whats the fuel pressure?

 

Hello Hoonk, and Thank you very much for the diagnostics information.
I followed them with little luck. I then replaced the rear oxygen sensor.
At this time, I got a different error code, PO134 (Oxygen Sensor Circuit No Activity Detected (Bank 1, Sensor 1), or the O2 sensor stays lean).
I checked the Air Mass Sensor reading on VIDA, and it had about. 25 KG/H (it should have about 14 KG/H in idle when hot)
I replaced the air mass sensor, and this case is resolved—there is no check engine light.
VIDA is now reading at the Air Mass Sensor about 14 KG/H, and the front oxygen sensor is circulating between 0 and 1 V.
Please see attachments
I hope this will help other VOLVO owners.