how to test our O2 sensors?

[ken99287]

So what is the best way to troubleshoot our O2 sensors? The white wire coming from the O2 is grounded. The two black from the O2 measure 0L or something (I forget) but the two black on my new sensor measures 17 ohms. With the probes on the car side harness that connect to the two black wires on the sensor, I'm getting 14v.

Are these values ok?

Is there a step by step troubleshooting guide for our O2 sensors?

I'm assuming my O2 sensors are faulty since I'm not getting the correct resistance between the two black wires.

I'm getting O2 codes for both sensors for faulty heater circuits.

[kumquat]

What code are you getting?

[ken99287]

P0135 and p0141

[kumquat]

Engine off, ignition on. Disconnect the sensor and test the voltage on pins 2 and 3 (black wires) to ground.

[ken99287]

Engine off, ignition on. Disconnect the sensor and test the voltage on pins 2 and 3 (black wires) to ground.

Ok, the two wires that feed to the black wires, right?

One of them, the black one gives me 12v when grounded.

The other, the red one with black stripe gives me 0v when grounded.

[kumquat]

Is that the rear sensor? I guess I was looking at the front sensor.

For the rear:
The black wire is "feed circuit"
Pink/black is "heater control"
Brown is "ground"
White is "heater control"

I believe pink/black and white should both give ~12V to ground (brown) when ignition on engine off. Black shouldn't give anything because that's the sensor wire.

[ken99287]

Well from what I understand, one wire will be ground, one wire will be the signal from the o2 sensor, and two wires will be for the heater (works like a light bulb, resistance causes heat). I know the two black wires on both original sensors was full open when they should have 16 ohms resistance. That tells me the heater circuit in the sensor is bad. The white wire was grounded according to the meter. The only wire left, the light blue, must be the signal wire. O2 sensors generate their own voltage depending on the amount of O2 in the exhaust compared to the amount of O2 in the ambient air. This signal must be sent through the blue wire. So of all the wires in the O2 sensor, there really only should be one hot wire - one of the wires feeding the heater circuit.

I went ahead and installed the new sensors. I suspect it will solve the issue.

Thanks!

[ken99287]

So far so good! No CEL so far. I got the denso 234-4209 universal and spliced it onto my old harness.

They are $37 at amazon, but I bought them at advance for $51.xx each and used a $50 off $100 purchase. Worked out well!

[kumquat]

Rad.