P0141 O2 Sensor Heater Failure Diagnosis

[EricTheCarGuy]

This was a fun video to make as everything pretty much fell into place except for the access to the sensor itself.

I’d also like to post a link to the article I wrote about this too.

http://www.ericthecarguy.com/component/content/article/23-obd-codes/obd-ii-codes/141-p0141-p0135-p0147-p0155-p0161-p0167-02-sensor-heater-circuit-malfunction

Topic

[twiggy]

My sister-in-law just had a similar code and had her sensor replaced- I believe it was an A/F Sensor not an o2 sensor. She gave me the old sensor to bring back to my lab to evaluate it and x-ray images show that the heater wires were open. Cutting the sensor open I co uld see that these wires were badly corroded.

Here is an x-ray pic. It’s hard to see but both wires thin down to nothing at the arrows and one of the wires lifted from the graphite heater element.

Attachments:

• Presentation4.jpg

[1sickaccord]

Hey Eric,

I saw on your OBD-2 scanner that was code 1 of 5, what were the other 4? :stick:

[EricTheCarGuy]

[quote=”twiggy02919″ post=35325]My sister-in-law just had a similar code and had her sensor replaced- I believe it was an A/F Sensor not an o2 sensor. She gave me the old sensor to bring back to my lab to evaluate it and x-ray images show that the heater wires were open. Cutting the sensor open I co uld see that these wires were badly corroded.

Here is an x-ray pic. It’s hard to see but both wires thin down to nothing at the arrows and one of the wires lifted from the graphite heater element.

[/quote]

That’s darn handy. I wish I had one of those to play with.

[EricTheCarGuy]

[quote=”1sickaccord” post=35357]Hey Eric,

I saw on your OBD-2 scanner that was code 1 of 5, what were the other 4? :stick:[/quote]

I wanted to stick to just the one code for the video especially since the other codes were not that common. I did however shoot additional video of it, it’s available to Premium Members.

[ridinred24]

Watching this video saved me an 02 sensor. I put an aftermarket exhaust manifold on my sisters 97 civic and noticed the hole wasnt compeletely machined out like yours was. A bit of work with a drill and I got the sensor to fit without touching. Kudos!

[EricTheCarGuy]

[quote=”ridinred24″ post=52813]Watching this video saved me an 02 sensor. I put an aftermarket exhaust manifold on my sisters 97 civic and noticed the hole wasnt compeletely machined out like yours was. A bit of work with a drill and I got the sensor to fit without touching. Kudos![/quote]

Good find! I’m glad my mistake was able to help you.

[Jack Patteeuw]

[quote=”EricTheCarGuy” post=35379][quote=”twiggy02919″ post=35325]My sister-in-law just had a similar code and had her sensor replaced- I believe it was an A/F Sensor not an o2 sensor. She gave me the old sensor to bring back to my lab to evaluate it and x-ray images show that the heater wires were open. Cutting the sensor open I co uld see that these wires were badly corroded.

Here is an x-ray pic. It’s hard to see but both wires thin down to nothing at the arrows and one of the wires lifted from the graphite heater element.

[/quote]

That’s darn handy. I wish I had one of those to play with.[/quote]
Don’t forget to order an electron microscope at the same time ! :silly:

[Jack Patteeuw]

Possibly a “nit”, possibly not.

In the video, you said there there would be 12V at the harness with the “key on”. Some cars may not power up the heater circuit until “key on, engine running”.

[twiggy]

[quote=”theoldwizard1″ post=60869][quote=”EricTheCarGuy” post=35379][quote=”twiggy02919″ post=35325]My sister-in-law just had a similar code and had her sensor replaced- I believe it was an A/F Sensor not an o2 sensor. She gave me the old sensor to bring back to my lab to evaluate it and x-ray images show that the heater wires were open. Cutting the sensor open I co uld see that these wires were badly corroded.

Here is an x-ray pic. It’s hard to see but both wires thin down to nothing at the arrows and one of the wires lifted from the graphite heater element.

[/quote]

That’s darn handy. I wish I had one of those to play with.[/quote]
Don’t forget to order an electron microscope at the same time ! :silly:[/quote]

Funny you should mention the electron microscope because we have two of these in our lab which we need due to the circuitry being so tiny for those cases where the optical microscope won’t do.

[Mike]

Excellent video on the o2 sensor itself for P0141 code. I have an identical Acura as in your video and have a question/comment on the Control Module side of the circuit:

While also isolating my P0141 problem to be an open-circuit in the sensor, I wanted to also verify the that proper power and ground were on the control module side of the sensor connector as you mentioned in the video. Power is there when the ignition key is ON; however, I cannot see ground being connected (by the ECM/PCM) when the key is ON. Looking at the electrical interface in the shop manual, the o2 sensor’s ground circuit is switched to chassis ground under control of the ECM/PCM. Is there a chance the ECM/PCM is not allowing the heater circuit to be enabled while the fault code is present? Is it a valid test to put an voltmeter across the 2 black wires and see power when the ignition key is ON? I find it hard to believe that both the o2 sensor failed and the control module failed at the same time! (Schematic is below and connector C611 is the one in your video.) Thoughts?

Attachments:

• Schematic.JPG

[twiggy]

[quote=”mav-01″ post=116657]Excellent video on the o2 sensor itself for P0141 code. I have an identical Acura as in your video and have a question/comment on the Control Module side of the circuit:

While also isolating my P0141 problem to be an open-circuit in the sensor, I wanted to also verify the that proper power and ground were on the control module side of the sensor connector as you mentioned in the video. Power is there when the ignition key is ON; however, I cannot see ground being connected (by the ECM/PCM) when the key is ON. Looking at the electrical interface in the shop manual, the o2 sensor’s ground circuit is switched to chassis ground under control of the ECM/PCM. Is there a chance the ECM/PCM is not allowing the heater circuit to be enabled while the fault code is present? Is it a valid test to put an voltmeter across the 2 black wires and see power when the ignition key is ON? I find it hard to believe that both the o2 sensor failed and the control module failed at the same time! (Schematic is below and connector C611 is the one in your video.) Thoughts?

[/quote]

That NPN transistor in the schematic needs its collector biased for it to switch. That might be why you are not seeing anything with your DMM whether you tried to measure ohms to ground or voltage across the heater terminals.

A 1000 ohm resistor would work if you connected that in and wanted to see if the ECM switched.

Or you can do this with power off only !: The transistor is sitting in type substrate and the collector is n-type so you could at least verify continuity through the ECM by setting your DMM to diode mode and connecting it backwards between the switched heater terminal (transistor side) and ground. The DMM should show you a forward diode reading if the schematic is accurate.

[Author]

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