986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Please confirm my diagnosis of one bad O2 sensor

Timbert · 12-24-2015, 01:46 PM

Replaced the MAF with a new genuine Bosch one from Rockauto, disconnected battery for ten minutes, and after a drive cycle the CEL came on and still reports 4 bad O2 sensors. No voltage swings from O2 sensors, Durametric shows -0.41 volts steady. The O2 heater resistance reports 4.1 ohms when the spec calls for 3.1 +/- 0.3 so I'm off a bit there but can't believe that's the problem. The front O2 sensors are brand new and idle is smooth.

I pulled the oil fill cap and still the fuel trims did not change nor did the O2 sensors vary their voltage.

What am I doing wrong? Would a bad DME do this? If I had a vacuum leak or fuel delivery problems I should see the fuel trim responding, right?

12-24-2015, 01:46 PM	#6
Timbert Registered User Join Date: Sep 2015 Location: Phoenix Posts: 15	Replaced the MAF with a new genuine Bosch one from Rockauto, disconnected battery for ten minutes, and after a drive cycle the CEL came on and still reports 4 bad O2 sensors. No voltage swings from O2 sensors, Durametric shows -0.41 volts steady. The O2 heater resistance reports 4.1 ohms when the spec calls for 3.1 +/- 0.3 so I'm off a bit there but can't believe that's the problem. The front O2 sensors are brand new and idle is smooth. I pulled the oil fill cap and still the fuel trims did not change nor did the O2 sensors vary their voltage. What am I doing wrong? Would a bad DME do this? If I had a vacuum leak or fuel delivery problems I should see the fuel trim responding, right?