SS #670 Mods: Wideband oxygen sensors

SS #670 Modifications:
Wideband oxygen sensors

I wanted to do some tuning with EFILive so I needed a wideband oxygen sensor. I decided to get a PLX Devices M-300. The M-250 would have been adequate but I thought the LED display might be nice and it was only $30 extra. PLX controllers feature sensor self calibration. The M-250 and M-300 uses the less expensive Bosch LSU4.2 heated O2 sensor.

I considered installing a new O2 bung but the best suitable location is on the top side of the bank 2 (passenger side) catalytic converter pipe above the bank 2 primary sensor. This would require dropping the catalytic converter to do drilling and welding. Since I didn't plan on leaving the wideband sensor permanently installed I chose to temporarily replace the narrow band sensor and feed the PCM the narrow band output from the M-300 controller.

The PLX Devices Stock Narrowband Sensor Replacement application note says to wire a 20 Ω, 10 watt load resistor in place of the factory H2OS header circuit. This is probably to avoid trouble codes with configurations that monitor the heater circuit. This isn't necessary with a late model F-Body since the PCM assumes that if the sensor starts producing voltage within a reasonable amount of time, the heater is working correctly.

Since I wanted to feed the narrow band input back into the HO2S connector, I opted to get power there too. This made wiring pretty simple. One good option is to cut a pigtail off of an old sensor. I didn't have one so I bought a Caspers Electronics oxygen sensor extension harness. Part 109007 is 24" long and has the necessary 4-way Metri-Pack 150 series female connector. I cut it and spliced in some longer wires along with a 4-way molex connector. I used a 2-way molex for the wideband output. This leaves the M-300 controller box with fairly short cables coming out of it. Finally I used some 1/2" convoluted tubing to bundle the PLX cable and the other wires.


HO2S connector	Wiring harnesses

Wideband wiring schematic

I routed my harness through the PCM hole in the firewall and wedged the controller box between the passenger carpet and transmission tunnel.

Installation notes

I used sensor safe anti-seize on the O2 sensors (AC/Delco 5613695). It's a special paint that consists of graphite and glass beads suspended in fluid.
The Performance Tools W84008 O2 sensor wrench worked pretty well on the wide and narrowband sensors.