2002 Blazer

No O2 codes, but all 3 passenger side plugs carbon fouled. Fuel Pressure leakdown test was fine, held to 55psi 10 mins. The Cat was also rattling and in is in process of being replaced with the O2 sensor.

The first pic shows my test method,
The second pic shows that both my voltmeter and my ground are good; it's reading a AAA battery just fine.

I can't get the needle to move at all with either of the existing sensors or the 1 new replacement ACDelco sensor. I don't believe the driver's side sensor is bad.
I think I watched 5 youtube vid's all doing the exact same thing but for some reason it's not working.

Applied propane torch up to 20 seconds until red, then applied flame intermittently. After that didn't work several times, I continued with direct flame up to 60 seconds on the new one, with the inner part glowing red over about 40% of sensor.
I hope this wouldn't damage it? Propane is around 2-3,ooo degrees F and exhaust would be a lot less than like 1,000+.
Positive lead probing blue wire terminal inside conncector, and ground connected to sensor body (vise grips).
(blue,white,black,black wires)

$15 analogue voltmeter, works fine for most things.
Set at 2.5V DC Current. I was extremely cautious to set it correctly before applying the test lead, so no power was applied to circuitry. It's probably not a 10 MegaOhm (which protects delicate auto electronics), but if I'm only testing for DC Volts, I don't think that would be a problem.
I know there are a few other tests to do regarding resistance, 12V power at the plug, etc, but have not looked into that yet.

I'm wondering if it's possible the new one was shipped DOA? Or if there is some way I'm doing this incorrectly.

Thanks!

 

Replying to my own thread. Very possibly BAD Idea to do this with torch. I know there are lots of people and videos that say it's the way to do it. I just spoke to a chevy parts guy and he sounded familiar with that and was adamant that you should never apply flame to a sensor.

 

No O2 codes would be a good indication the sensors are ok. Why not just watch O2 sensor voltage on a scan tool while the engine is running? Were there any codes in memory? Was/is the check engine light on?

 

I have CEL on: codes 452 and 0300, but No sensor codes. Tuneup will be next after sorting this out. Fuel leakdown just passed: 59psi, then 10 minutes down to 50psi, but at night with cooling weather.

Just replaced Bank 2 -passenger side sensor with new ACDel. This was done due to 3x fouled plugs on passenger side & poor fuel economy, is running a bit better, no fuel smell in exhaust.

Then found the Voltage Readout on the app, great option, Thx!

Some unexpected results.

Bank 1 is sometimes spot on, .15 - .9 steady flux. It also varies quite a bit, maybe that's normal. Should I assume this one is fine based on output below?

Bank 2 -passenger side, new ACDel replacement (minus bench test maybe scorched it) is peaking at .44max, which is same as nominal voltage when not running. It has variation ranging from 0 to .44.

I tested each side with sensor wires disconnected to make sure it's the new one that's failing. The old sensor just flatlines at .44V when disconnected.
The voltage on the passenger side new sensor was fluctuating with the sensor wire disconnected (when the other side was on). It did flatline when both sides were disconnected.

Maybe that's indicating that the Input voltage is fluctuating and that's the problem, not the sensor? But with both sensors dissabled, they both flatline, so probably not. It almost seems like there's a feedback loop between the two.

Should I replace both? or just the brand new one that's reading .44max?
Or is something else going on that needs looking at?

I should probably check by swapping sensors, but maybe these results are enough to say Bank 2 needs replacing.

Thanks!

The progression of these readings is; 1) idle/revving to 2k; 2)Bank 2 disconnected; 3) both disconnected; 4) Bank 1 disconnected; 5)idle again both connected; 6)Driving

 

While running, the PCM is constantly varying the injector pulse width to run the mix from lean to rich, so the bank 1 sensor is working properly with wide fluctuation of the voltage. The lack of higher voltage from bank 2 indicates you maybe fried the sensor. Try swapping sensors to the other bank and see if the problem follows the sensor or stays on bank 2.


The 4 wire sensors do not ground through the shell of the sensor, 2 wires in the connector are the sensor signal and 2 are the heater element. Connecting the test lead to the shell should read 0 volts.

 

To take the guessing and worrying out of your mind..Just replace all of them.That way you`ll have a piece of mind.I have a 2001 Ls Blazer with the 4.3 vortec.The (service engine soon) light came on about a month ago.So later on that week the light went out.So I decided to change both of my o2 sensors.I have only 2 of them before the cat.ever sense then the light never once came back on.Plus I get a little bit more mpg.