O2 sensor voltage help!!!! - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

CSXTacy · 04-18-2007, 07:10 AM

ok i installed my wiring harness today and started checking voltage to all sensors, (Oh BTW i am working on a 89 hatch with a redtop Sr20DET)
I was checking voltage to my o2 sensor to make sure it was wired right and
i have came to find out that when the computer is hooked up i have voltage to all three wires. i am getting the proper 12V to the brown wire but the white wire and the black wire are both getting around 10 volts constant when
the key is on. now when i disconnect the computer the voltages in the white and black wires disappear. can anyone tell me what the proper voltages to each wire should be??? i know there shouldn't be any voltage to the black wire at any time but should the white wire be key on the same way the brown wire? and if it is what voltage should it be producing? could this be a fault in the computer? and if it is would a black top computer work just for testing?? i searched the forums and could not find anything relating to this problem any tips or suggestions would be greatly appreciated!!! My first SR20DET is soooo close to starting figuring out this problem would be a
great help!!! THANK YOU!!!

CSXTacy · 04-18-2007, 11:02 AM

bump Anyone?

Big Bronze Rim · 04-18-2007, 07:35 PM

Something is definitely not wired correctly. The white wire is the signal wire and should be a 0-1V signal which is produced by the sensor itself. You should have 12V at the brown wire with the key on. The black wire is the heater ground which is controlled through the ecu. With the key on, the black wire should be grounded by the ecu to warm up the sensor, so that is why you are seeing some voltage across the sensor (there will be some voltage drop due to the resistive heating of the sensor). However, the white wire should NOT EVER see more than 1V at the ecu. Its quite possible that you may have already damaged the ecu by sending 10V to the input. I dont know what kind of voltage protection circuitry the ecu has for o2 input. Check all your wiring again.

g6civcx · 04-18-2007, 07:52 PM

You need to search the word "o2 sensor". You will find my post describing the proper 3 wire o2 sensor.

The middle is signal. This goes to the ECU.

The two outside wires are non-polar 12(+) and ground (-) with key ON. It doesn't matter which is which as long as both wires are connected. Current will flow either way.

04-18-2007, 07:10 AM	#1
CSXTacy Leaky Injector Join Date: Jun 2006 Location: Cedar Rapids IA Posts: 74 Trader Rating: (4) Feedback Score: 4 reviews	O2 sensor voltage help!!!! ok i installed my wiring harness today and started checking voltage to all sensors, (Oh BTW i am working on a 89 hatch with a redtop Sr20DET) I was checking voltage to my o2 sensor to make sure it was wired right and i have came to find out that when the computer is hooked up i have voltage to all three wires. i am getting the proper 12V to the brown wire but the white wire and the black wire are both getting around 10 volts constant when the key is on. now when i disconnect the computer the voltages in the white and black wires disappear. can anyone tell me what the proper voltages to each wire should be??? i know there shouldn't be any voltage to the black wire at any time but should the white wire be key on the same way the brown wire? and if it is what voltage should it be producing? could this be a fault in the computer? and if it is would a black top computer work just for testing?? i searched the forums and could not find anything relating to this problem any tips or suggestions would be greatly appreciated!!! My first SR20DET is soooo close to starting figuring out this problem would be a great help!!! THANK YOU!!!

04-18-2007, 11:02 AM	#2
CSXTacy Leaky Injector Join Date: Jun 2006 Location: Cedar Rapids IA Posts: 74 Trader Rating: (4) Feedback Score: 4 reviews	bump Anyone?

04-18-2007, 07:35 PM	#3
Big Bronze Rim Zilvia Member Join Date: Jan 2006 Location: San Antonio, Texas Age: 46 Posts: 173 Trader Rating: (0) Feedback Score: 0 reviews	Something is definitely not wired correctly. The white wire is the signal wire and should be a 0-1V signal which is produced by the sensor itself. You should have 12V at the brown wire with the key on. The black wire is the heater ground which is controlled through the ecu. With the key on, the black wire should be grounded by the ecu to warm up the sensor, so that is why you are seeing some voltage across the sensor (there will be some voltage drop due to the resistive heating of the sensor). However, the white wire should NOT EVER see more than 1V at the ecu. Its quite possible that you may have already damaged the ecu by sending 10V to the input. I dont know what kind of voltage protection circuitry the ecu has for o2 input. Check all your wiring again.

04-18-2007, 07:52 PM	#4
g6civcx Post Whore! Join Date: Apr 2004 Location: Virginia, USA Posts: 5,764 Trader Rating: (5) Feedback Score: 5 reviews	You need to search the word "o2 sensor". You will find my post describing the proper 3 wire o2 sensor. The middle is signal. This goes to the ECU. The two outside wires are non-polar 12(+) and ground (-) with key ON. It doesn't matter which is which as long as both wires are connected. Current will flow either way.