I've been getting P0150 Fault Codes recently. I understand that this relates to the 'circuit' and not the fuel mixture. Anyway, I have software and dongle to interface with the car myself so i'm fortunate that I can take my time and try different things.
After weeks of getting the engine light every 200 miles or so I managed to catch the problem while was happening real time. I noticed that if I messed around with the connector block for sensor 1 on bank 2 I could get the voltage reading to alter and sometimes completely disconnect. I've since removed the connector block and soldered the joins between loom and sensor and I now seem to be getting a good strong connection with good sensor readings.
During testing the fuel trim and voltage on sensor 1 on bank 1 and bank 2 for comparison I noticed on tick over the fuel trim on bank 1 moves between -5 and +5 as normal, but the fuel trim on bank 2 seems to slowly creep up to +25 which is where it stays until I depress the throttle. This is not normal obviously. Howevre the voltage on sensor 1 bank 2 is moving around more or less the same as bank 1.
I then checked the voltage reading from sensor 2 on bank 1 and 2. I can see that the voltage on bank 1 is moving around in line with sensor 1 on that side. But sensor 2 on bank 2 is showing a flat line on voltage. If I press the throttle the voltage drops and then goes back to the flat line.
I'm wonding if there is something wrong with sensor 2, which is causing the fuel trim to steadily creep up on bank 2?
Oh, I should also mention that while the fuel trim is creeping up on bank 2 on tick over, tick over gets more and more rough. As soon as use throttle, smooth as you like.