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O2 sensor values

6K views 5 replies 2 participants last post by  Bernard1975 
#1 · (Edited)
Chrysler 300C HEMI AWD 2005, maintenance up to date. 80K miles.
Since the dealer replaced all 4 O2 sensors the car bucks and shudders, misfire when in lock up and slow acceleration.
Also at idle it doesn't feel right.

During changing out the O2 sensors the mechanic got a code open circuit and he reversed two wires from one sensor.
This was quite strange, because it should be plug and play. Old ones out, new Mopar ones in.
And then the issues started, bucking, shudder, misfire. Almost every sensor has been replaced.
Also sparkplugs and coils, plugs were not wet or white, just like they should be.
Even the PCM was changed, but still with the O2 wires reversed on one sensor. When the new PCM was installed it ran fine the first minutes..... untill warm.
Is it possible that because of the reversed wires the PCM got a circuit problem and PCM gives me these problems?
On the O2 sensor 1-1, i see a reference voltage with KOEO of 4.78V, while the other 3 are 4.98V and 5V.
How can i solve this? I saw a TSB with repair guide for O2 connectors model 2005-2006.
Could this be the issue? Also because of the open circuit warning.

The downstream O2 sensors are also pretty low voltage wise, they generate around 2.5V at idle and goes up when driving, but they can also drop from 3.3V to 2.9V and then go back.
Should the downstream sensor stay at the same voltage? Or can they swing a little bit?

Last time they changed all O2 sensors again, and also got the wiring back to normal, ofcourse same problem.
Maybe a new PCM could solve things now together with new connectors for O2 sensor 1-1?

Well, maybe someone knows the solution. Many thanks for helping.
 
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#2 ·
What are you reading these voltage numbers with?

The O2 sensor heater voltage should be around 12 volts.
The running reference voltage (what goes to the PCM) should oscillate from approximately 30mV to 900mV

A dead sensor reads in the 400mV range.

So it needs to be clarified, are you talking about the heater voltage or reference voltage. The heater wires can most of the time be switched, they're not polarity specific.

If you're reading dead O2 sensors did someone mess with the ASD relay? Theres a modification on the internet that instructs to bypass the ASD relay and when this is done it fries the drivers in the PCM.

Heres a picture of a scanner showing normal O2 sensor oscillation. They are running from 38 to mid 900mV.

 
#3 ·
I read them with Diablo sport tuner.
I am talking about reference voltage coming from PCM, KOEO.
Can you see reference voltage?
Nice chart, good way to check things.

ASD: i saw that trick on the web somewhere, but no, not on my car.

The other two wires were reversed, not the ones from the heater voltage. Voltage is just above 12V.
I don't know if the PCM can be screwed if you reverse the other two wires, that is reference 5V wire and signal return?

Thanks for helping out!
 
#4 ·
I've never used the Diablosport tuner, not familiar with it.

I can't see reference voltage with my tuner. I don't think I can anyway, if the signal voltage is oscillating properly theres no reason to read the reference voltage and I've never had to read it. I may have read it with a DVOM when splicing those crappy universal sensors that have you reuse the original plug.

That tuner doesn't have the ability to read the voltage like I did in the chart above?

You are correct, the other two are 5 volts reference and return. I have no idea why the guy would reverse those on purpose.

Maybe check all of your grounds and see if you can get a chart like mine. That chart is good for a lot of things, even bad fuel injectors and stuff like that. I'd be curious to see what your O2 sensors are putting out.
 
#5 · (Edited)
The both upstream sensor are swinging from 2.5V to 3.3V, or 0.1-0.9V, in a constant rate.
But what i found interesting in your data:
Accelerator pedal position 1: 0,00V, mine is at 0.45V. Accelerator pedal position in % is 0.
Throttle position sensor 1: 0.65V

The mechanic had a open circuit warning. Because of this he reversed the wires. Then the car ran like s...t. Everything on the car is mopar/original.
 
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