DME: Trimming, oxygen sensor before cat., Bank 2
 

After searching the forum and having found numerous threads about it, I'm totally confused. I hope someone can help me with this. I have a 2006 3.0 that just started throwing the code above. I've cleared it a couple times and it comes back. So I opened up the OBDII and got the live data. The live data is below. I hope someone can tell me what I'm seeing.

Load PCT: 5.5%
ECT: 203F
SHRTFT 1: varied between -1.6 to -3.1%
LONGFT 1: 6.3%
SHRTFT 2: varied between 0 to -3.9%
LONGFT 2: 7.0%
RPM: varied 774 to 781
Spark Adv: varied -2.5 to -3.5
IAT: 151F
MAF: .01lbs/s (calculates to 4.54 grams)
TP: 9.8%
O2B1S1: varied .130 to .730V
SHRTFTB1S1: varied -1.6% to -3.1%
O2B1S2: varied .750 to .770V
SHRTFTB1S2: 99.2%
O2B2S1: varied -.135 to .750V
SHRTFTB2S1: varied 0 to -3.1%
O2B2S2: varied .720 to .750V
SHRTFTB2S2: 99.2%

Thanks for any help you guys can provide. I'm not even sure where to start.

O2 can't range to negative values. The precat if reading negative values something is wrong. Looks like a case of problem sensor.

Also: post cat should gravitate to 0.45V so the 0.75 is very high but that can vary a lot.

What I would do: reset all the sensors by unplug them all, start the car run until you get multiple errors (probably missing O2 heater error) then plug them back in and clear the codes.

See if the numbers will come back into normal range (0.1 to 0.9v).

If you get values outside of normal you probably need to replace the sensor (use OE or OEM don't cheap out: I need to replace my knock off sensors)

I should have said I recently replaced all of my O2 sensors using Bosch replacements.

So if you are getting out of possible range it's either a bad sensor or problem in the ECU. The easy test is swapping the two pre cat sensors and resetting adaptations (or as described above recalibrate the DME)

I just tried recalibrating the DME and resetting adaptations. No change.

I'll try swapping the sensors this weekend if the weather cooperates.

Swap the pre cat sensors and see if the problem migrates. It feels like a bad new sensor to me.

I'll try it. I hope that's all it is. FCP will replace it for free!

Actually, for Short term fuel trim or long term fuel trim the value can be negative or positive. Negative STFT will mean that the DME is taking away fuel and positive STFT will mean the DME is adding fuel to the mixture.

The post cat 02 voltage should be at a constant value whereas the pre cat 02 sensor the voltage will vary.

Here's a video on 02 sensors as it relates to voltage

https://www.youtube.com/watch?v=zyh_4SktmFM

Here's a video on STFT vs LTFT. You can see that the STFT is negative because the LTFT is positive and the DME is trying to zero out the fuel trim.

https://www.youtube.com/watch?v=WMSM7WAbBss