Technical O2 lambda sensor replacing

[Theleman]

The new sensors now in the car, DMM readings,

The top one: 6 ohms
The bottom one: 7 ohms

Voltage from the car to the top sensor: 3.45 V
Voltage from the car to the bottom sensor: 3.46V

Are above voltages from the car to the sensors OK?

The EML has returned this morning.

What should we look into now?
I am going to disconnect the battery in the car for an hour, and reconnect, and do another computer erase the code P0135, and check it again.

But any idea, info or advice would be much appreciated. Thanks.

 

[koalar]

The garage that did the clutch hasn't swapped the connectors over by accident?


The connectors are the same.

 

[Theleman]

The garage that did the clutch hasn't swapped the connectors over by accident?


The connectors are the same.

Yes, the connectors look exactly the same, but does it have to fit to the right one?
Does it matter which connector fits to which sensor?

 

[koalar]

One probe on one of the White wires the other to the chassis should measured around 12V give or take


The sensor is quite well sealed for back probing. I have tried with a pin at the back and the reads aren't right

I imagine the back of the connector it plug into would be better

Engine has to be running and cold

 

[koalar]

Yes, the connectors look exactly the same, but does it have to fit to the right one?
Does it matter which connector fits to which sensor?

Yes

 

[Theleman]

One probe on one of the White wires the other to the chassis should measured around 12V give or take


The sensor is quite well sealed for back probing. I have tried with a pin at the back and the reads aren't right

I imagine the back of the connector it plug into would be better

Engine has to be running and cold

It was only reading 3.46V, but then I just turn the ignition on not starting the car.

Will need to try again with the car running then.

Now I have disconnected the battery, so the onboard computer would be rebooted cold.

 

[Theleman]

Yes

Will try to swap over the connectors to each sensors after reconnecting the battery.

I am not sure what the garage had done to the cables or sensors. Only thing we noticed was that the EML came on just after the cultch replacement.

 

[koalar]

Don't do this yet. Have to think about this


You have an old sensor. Cut the wires off


Strip the two White leads and solder a 12V bulb to the wires as long as the resistance is higher than the heating element it should be safe and give a visual indication when the heater circuit is working

 

[koalar]

Even easier


One of your sensors heating element measures correct


Plug it into the top sensor connector you should feel it heat up. As long as the engine is cold and just started.


The post CaT doesn't need a heater I am not sure if its even functional on the Panda.

 

[Theleman]

Even easier


One of your sensors heating element measures correct


Plug it into the top sensor connector you should feel it heat up. As long as the engine is cold and just started.


The post CaT doesn't need a heater I am not sure if its even functional on the Panda.

Great idea. Will try that this afternoon, and update how it went.

 

[Theleman]

Started the engine and running, measured the voltage getting fed to the white wire in the sensor. It is only 3.6V at max. Both clip white wire tapping are exactly same voltage reading max. 3.6V, but it fluctuated from 0.5 - 3.6V on the DMM.

Is is not supposed to be 12 - 13V normally?

 

[A3jeroen]

Voltages coming from the ECU are usually 5V max. You'll probably burn the sensor out if you feed 12V to it.

gr J

 

[Theleman]

Voltages coming from the ECU are usually 5V max. You'll probably burn the sensor out if you feed 12V to it.

gr J

But this is supposed to be the input voltage supply to the O2 Sensor heater, nothing to do with the ECU here?
The signal wires would carry the O2 generated voltage which is 0.9 - 1 V to the ECU?
ECU is not feeding the heater supply, is it? ECU gets fed the generated voltage from the sensors, to reiterate?

Car battery 12V ===> ???? === > Clip (white wire sends out 12V) ==> Clip of the O2 sensor (white wire receives 12V ) ==> O2 sensor heater (heats up) ==> generates voltage (0.9 - 1V via the signal wires) ==> ECU?

I am wondering if there is something (noted as ????) in the link above, which downed the voltage from 12V to 3.6V in above chain, which makes the sensors not functioning?

Because right now, this is happening.
Car battery 12V ===> ???? === > Clip (white wire sends out 3.6V) ==> Clip of the O2 sensor (white wire receives 3.6V ) ==> O2 sensor heater (fails heating up) ==> generates no voltage (signal wires = ???? ) ==> ECU (&%????) ===> EML?

 

[Theleman]

Got the above idea from here.

https://autoditex.com/page/lambda-sensor-o2-sensor-21-1.html

 

[Theleman]

I was wondering if the garage man, who replaced the clutch last year, have pulled out the 12V supply cable to the sensors heater, then plugged them back onto somewhere else, which is outputting 3.6V. Just guessing.

 

[koalar]

Yes its feed 12V from memory via a relay


ECU switches the negative side to time how long its been on. Also uses this connection to sense if there is a problem

The heating element in O2 sensors are normally rated to 20V

 

[koalar]

Should have mentioned

If the ECU has detected a problem in the past. It will not switch it back on until the code has been cleared

 

[Theleman]

Yes, my local friend told me on the phone something similar. He knows about cars more than me due to his work experience in garages before. But I wasn't sure if it is true.

With my £15 Code reader from Amazon, even if I cleared the code, it will not clear the code properly, and it will keep coming back.

He told me that, when the old sensors are replaced with the new ones, I must take the car to a garage who has a proper computer to clear the code. Is this true?

 

[koalar]

Yes, my local friend told me on the phone something similar. He knows about cars more than me due to his work experience in garages before. But I wasn't sure if it is true.

With my £15 Code reader from Amazon, even if I cleared the code, it will not clear the code properly, and it will keep coming back.

He told me that, when the old sensors are replaced with the new ones, I must take the car to a garage who has a proper computer to clear the code. Is this true?

Never heard that before


There's some codes that will not clear. But haven't seen a generic engine code fail to clear before

 

[Theleman]

Never heard that before


There's some codes that will not clear. But haven't seen a generic engine code fail to clear before

Yeah, I thought that was a bit weird. I have not heard that either.