synrgy350

I have a strange problem with my IS350, when I'm reading the fuel trims with my tech stream, I've noticed bank 2 has a positive fuel trim of +10% which is abnormally high compared to bank 1 which is around 3-4%. What would cause one bank to need more fuel than the other? Is it possible to have a vacuum leak on just one bank? Any advice is appreciated. Thanks!

synrgy350

Anybody have experience with tech stream diagnostics?

DAng87

iTrader: (1)

i had an experience in another vehicle where i had an exhaust leak before any o2 sensors, this would cause the sensor to read extremely lean, thus ECU will compensate and dump fuel to try to get the right mixture. I was also getting horrible mileage

A1cntrler

iTrader: (2)

Can you check the O2 sensor on that bank? I know it probably isn't throwing a code, otherwise the car would let you know, but it may have just become inefficient?

Also as said above check for exhaust leak at mounting points (gaskets).

synrgy350

Thanks for the replies! I checked for exhaust leaks but couldn't find any. When scanning with the techstream, I noticed that the leaner bank's 02 sensor (post cat) has a much lower voltage than the normal bank, which makes sense since its running lean? I used the A/F sensor test function in techstream to test their response and they appear to function normally. I can't tell if bank 2 is lean due to a lazy sensor or if there are possible fueling/ vaccuum leak issues.

synrgy350

So heres my screencapture of testing the post cat 02 sensors while increasing and decreasing the injection volume. I assume that since my b2s2 reading is flatlining most of the time that its bad? Can a bad post 02 sensor increase fuel trims? I thought it was meant to only measure catalyst efficiency?