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.

Clear em and see if they come back.
Gilly

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Thanks Gilly. I cleared the codes a few days ago and no engine light yet but the idle is still sluggish. Thanks again.

Well, I just came back from the store and the engine light is back on. I checked the codes and this time it came back with P0130 & P0150. I think I will start with replacing the CPS and two front O2 sensors. the car is almost at 100k so I would think it would benefit from new O2 sensors anyways. thanks

Right, and the rear ones won't affect driveability, they only are used to monitor if the cats are working.
Gilly

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Most of the time the O2 sensor code indicates a bad MAF.

The fact that the exhaust mixture that reaches the sensor is something the sensor can't handle doesn't mean the sensor is bad.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles