My wife drives a 2001 ML320 and a week ago the speedo and tach needles started going crazy, up/down/up down, sometimes freezing in place and sometimes not even moving. Then several days ago the engine light came on. The very next day when we started the car it sputtered and stalled. After re-starting, it was ok but the idle was a little off. We also could not shift it into reverse. So we did the pen trick so we could shift it into reverse/drive. When we did so the idle went way down and the car sputtered but did not stall, when in park the idle gets smoother. The codes that I pulled were P0130, P0136, P0150 and P0156. These seem to be codes for all four O2 sensors. My question is, could all 4 go at the same time? Or is there anything else that could be causing the O2 codes to come on? The plugs, wires, alternator and brake light switch have been replaced within the last 2 years. I really do not want to take it to the dealer since $$ is a little tight. Any help will be greately appreciated, Thank you.