O2 sensor issue

[Marleez]

Had engine management light and traction control light on and got this error on diagnostics machine.

Cleared codes and I'll see if this pops up again. I always use BP ultimate. Today was the first time I used vpower.  May have been the fuel. Anyone else had this issue?

[Garth-1]

Not sure if it's connected with your problem but the very first time I put V-Power in my wife's MX5 it failed to start the next day and I called out the RAC.  Then the fault mysteriously cleared and it started OK.  Since then it's been very happy with V-Power, as are all of my cars, which I use whenever I can.

[Tyre Tread]

My car began with an intermittent fault on one of the O2 sensors (same symptoms as yours) and it became more frequent until I had to change the sensor. 

It was the left (N/S) upstream senor that went so i changed both upstream sensors because conventional wisdom is that they tend to go in pairs.

[Linas.P]

I really doubt the fuel could cause that, IS250 is really not picky when it comes to fuel ... I have ran it on E10 and even E85, various brands of "super market fuel" and never had a problem.

It may be the case that clearing codes will be all it needs, maybe driving it less often caused temporary issue. Secondly, it would be good to compare fuel trims on both banks to see if you have "lazy" o2 sensor - sometimes sensors starts getting faulty, but not enough to cause permanent fault in ECU. 

[Mihanicos]

This trouble code indicates too much air or not enough fuel to the engine for a stoichiometric combustion.

Check and clean the Mass Air Flow sensor.

Check that the air induction system  from the Mass Air Flow sensor and beyond is intact and does not suck any air in.

Check all ventilation hoses and ventilation valve for any damage.

Check A/F sensors of bank 2 and their heater and relay circuits.

Check engine coolant tempetature sensor.

Check for any gas leakage from the exhaust system.

If the above checks do not reveal the cause of the fault,  check the fuel injectors for any blockage and spray pattern.

Check the fuel pressure as well.

Start from the easy checks first.

Chris.

[Marleez]

The error hasn't popped up again. And I been back to using bp Ultimate. May have been some dodgy fuel. Car has been fine. 

[DannyM]

You need to look at your fuel trims with a scan tool to see what the management is doing. I had a rich condition recently with my 250 but on both banks. I knew it was highly unlikely both o2 sensors would fail at once. Diagnostics showed negative short and long term fuel trims on both banks indicating a false MAF reading. I cleaned the MAF and all returned to normal.

You need to log the short term fuel trims for both banks and see what's going on. If your fuel trims are positive, the ECU is adding fuel because the o2 sensor sees the mix as lean. On the other hand, if the fuel trims are negative, the o2 sensor sees the mix as rich and is subtracting fuel. If your trims are within +/- 5% on bank 1 then you're o2 sensor is reading correctly. If both banks are showing similar fuel trims then it's more likely a MAF issue. Pre-o2 sensor holes in the exhaust can also create false readings as a venturi effect will draw ambient air into the exhaust flow and tell the sensor it's lean.

I'd start with comparing your fuel trims between banks and look for an imbalance. Being you have a lean condition your trims will be positive. If it's good on bank 1 and not on bank 2, focus your attention towards o2 sensor and or a pre sensor exhaust leak. If both banks show negative even if bank 1 hasn't triggered a fault code yet, I'd be looking at the MAF sensor.

 

Hope that helps,

Daniel.