I'm wiring a wide band O2 sensor controller to the O2 inputs in a 98' 355. The wide band controller has four connections: 1. +12 VDC 2. Ground 3. Output 1 4. Output 2 I'm using one output as the simulated narrow band signal. BUT, here is my dilemma. The wide band controller has one ground for both the analog output and the power. The Bosch ECU has a separate, from chassis, ground for the O2 analog signal inputs. Should I do anything with the analog ground? I don't want to introduce noise to the ECU by tying it to the chassis ground and I don't believe it wise to use this as the controller ground. If I really really need a reference, the wide band controller has a second output the I can set to zero volts and use it as the ground reference.
The ECU has several grounds and all are connected together inside the wiring harness, then a single wire is brought out to the rear of the bank 1 head and grounded there. Bring your ground from the wide band controller to the same point.
On a Bosch 5.2, the cold point of the O2 sensors is not connected to the ground. There is an internal voltage divider which is used for the diagnostic of those inputs. Though, you can connect your controller between the hot input and a signal ground but you will have to add an offset to the output signal (# 730mV) for a correct reading by the Motronic.
So I should not use the signal common or cold point, pin 46. I'll use chassis for both power and signal ground. If I leave pin 46 not connected will it be a problem? Also, will I have to load the heater common?
Subbed Interested to see if it works, Please post what you do when you did it you know what I mean ? LOL
Thanks Eric. The jungle was quiet today so I did some testing. I connected the WB controller power to the heater +12 and the heater ground. I then connected the WB output to the signal input. I left the signal ground open. With the 730mv offset that Eric suggested, it all worked perfectly. I ran the left side with the WB and the right with the normal NB sensor. I watched the ECU status on the SD2 and both sides seemed similar. My next test is to run WB on both sides and alter the AFR and see if the ECU can tune to it.
