E36 318iS O2 Sensor F'ed Up

[smhheidari]

Hi there,
I recently bought a BMW E36 318iS Coupe, when i look under of the car i saw no  connector between the O2 Sensor and the wires from engine, i think the last owner cutted the the connectors i dont know why, there was, 4 wires from 02 sensor which was, 2 Whites, 1 Black and 1 Gray, and 4wires from the engine which was Yellow, Green, Brown and Black, now im confused how is the wiring?!
my car runs too rich about 15liters in 100km, how can i test my o2 sensor to make sure it works fine, and why the check light dont illuminate when there is no 02 sensor?!

Thanks!

[danlolasdad]

CHECK TO SEE IF THE BULB IS EVEN THERE OR REPLCACED WITH A BLOWN ONE DOES THE LIGHT COME ON WITH YOUR IGNITION I FOUND THIS BODGE JOB IN A COUPE RECENTLY IT WAS TO MAKE ABS LIGHT GO OUT VIA THE BATTERY LIGHT. I HAVE THE O2 WIRING DIAGRAM ON ANOTHER LAPTOP ILL CHECK THIS THREAD LATER

[smhheidari]

Thanks dude!

[bmwconnect]

Hi there,
I recently bought a BMW E36 318iS Coupe, when i look under of the car i saw no  connector between the O2 Sensor and the wires from engine, i think the last owner cutted the the connectors i dont know why, there was, 4 wires from 02 sensor which was, 2 Whites, 1 Black and 1 Gray, and 4wires from the engine which was Yellow, Green, Brown and Black, now im confused how is the wiring?!
my car runs too rich about 15liters in 100km, how can i test my o2 sensor to make sure it works fine, and why the check light dont illuminate when there is no 02 sensor?!

Thanks!

Hello,

You can test the o2 sensor with a propane torch and a volt meter that reads in mili volts. Once you have it at operating temp it should fluctuate voltage fairly quickly

[DesktopDave]

You should have wiring connector with four wires (it's a barrel twist connector called C140).  I don't have the e36 ATM, but the e30 is similar.  The four wires on the e30 are as follows:

Pin 1 - Yellow - sensor output to DME pin 71
Pin 2 - Black - sensor floating ground to DME pin 70
Pin 3 - Brown? - heater ground to splice  S111 (looks to be near the DME, maybe bolted to the firewall, glove box or plenum area)
Pin 4 - Grey/violet - heater power from the O2 relay

I'll bet yours match up, except for the green.  I'd figure that's pin 4, heater power.

The O2 sensors you'll get are likely to have different wire colors than the car as well.  They'll also usually have a pair of think wires (heater) and a pair of thin wires (sensor).  Those pairs are not critical, each can be wired either way.  Just be sure you don't mix up the heater & sensor wires!  The computer expects less than 1 volt off the O2 like BMWConnect said...12VDC will cook the computer in an instant!  The two thicker wires on a Bosch O2 sensor will be for the heater.  Many pre-cat Bosch O2 sensors will work in a pinch, they're all similar.

Test the wires with a voltmeter.  The O2 heater + will have 12VDC if the key is on.  The O2 heater - will have continuity to any ground.

[danlolasdad]

post and pre cat o2 sensor wiring schematic hope this helps