O2 on a 2000 Ex 5.0

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Kidd-7

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96 Cougar 4.6L
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My 2000 Explorer 5.0 has had intermittent rough running and lose of power. Looking at the data bank2 O2 was flakey, drops to 0 then FT bank 2 maxes out; power lose.
There was some oil on and in the connector, I cleaned it up and filled the connector with dicentric grease, she ran great for a few days and the data looked good.
Now I've got no signal from bank2 O2, but fuel trims look good, power is good, but idle is rough at times.

My question: could the oil have killed the O2? It doesn't look like the oil got onto the sensor itself.

Or could the oil have penetrated the connector giving me an electrical issue?
 
If oil got on the sensor element and burned off, I could see that damaging/killing it. I've read that the zinc/phosphorous does it. Not sure how much it would take to kill it though... :zshrug:
 
I doubt that happened as it’s screwed into the exhaust.
 
Yeah... it's more likely IMO that contaminants got into the connector and are messing with continuity.
 
That’s what I’m thinking also. At 23 years old even a hermetically sealed connector will probably leak.
I think I’ll grab some contact cleaner, clean it up well then seal it again. It did work for a couple days after cleaning.
 
Fault codes are: P0175 system too rich bank 2 & P1151 lack of upstream O2 switching
 
Sounds like heater voltage is getting into the signal. Clean out the connnector with maf cleaner spray, it won't hurt anything, unless you have electronic cleaner.
 
That’s what I did and it lasted a couple days. Gonna have to clean it more thoroughly.
Sounds like gunk is shorting the heater current to the sensor leads, huh?
 
Using some of the foaming engine cleaner I cleaned off the engine, oil pan, trans, etc. getting rid of a lot of gunk down there. I proceeded to thoroughly clean the connector.

I'm still having intermittent rough idle and low power issues. It seems to bog down in OD when trying to climb a slight incline. Once it downshifts and the RPMs rise she runs much better. I'll have some data to look at later today.

This connector is mounted vertically on a bracket on the side of the trans, if the seal has worn out it would be possible for debris to get into the connector from the top where the wires head up to the harness. I'd like to try sealing up around the wires, is RTV acceptable or is it conductive? Any other suggestions?

Another path may be replacing the connector and wiring. I've found new connectors online, but they all have short wires. Anywhere you know of to get a new O2 connector with a couple feet of wires?
 
I'm still wrestling with this beast; here's what I see in the data today:
- there is a pattern of very flat switching for all 4 O2s at the same times. Flat meaning the exact same Vp-p.
- In the EVTM all 4 signal returns meet at the same splice then onto the ECU with a few other sensors.
- It's during this time that the short term fuel trim on bank 2 maxes out.
- BK1 fuel trim is affected by this scenario, but to a much less degree

I am currently unsure what this means and am taking a walk to clear my head, any input is much appreciated. I can also share either screen shots or the excel file with the data.
 
O2 sensors are very high impedance, which means anything can dink with the signal. Clean it, and fill the conn with dielectric grease.
Old oil has carbon in it, which is conductive enough. The rear o2 sensors on ra have longer wires
 
Do you have a wideband to see if the narrowbands are switching at the right lambda? And cross-reference to see if the PCM's STFT matches the lambda read by the wideband?
 
I do not have a wideband.

Grog: I have cleaned the connector 2 or 3 times and it still intermittently performs this way.
 
Next question I guess would have made more sense to ask earlier... do you have a way to read what the commanded O2 voltages, STFTs (and LTFTs) are?
 
I’m using torque to log the data, not sure if that’ll give us what your asking.
 
If it Doesnt' work, you'll have to replace it.
 
Grog6 said:
If it Doesnt' work, you'll have to replace it.
Click to expand...
words of wisdom right there. and also if it ain't broke don't fix it.... :)

Now if you are referring to the O2 sensor, it's an intermittent failure, 2 different O2 sensors. Both perform with the same symptoms, I highly doubt it's the sensor.
 
Time to trace out the wiring, then. the signal wire needs to be over 1 Meg ohm to all other wires.
 
Ohm’d out the wire from the O2 to the ECU, no issues even while jiggling the wires.
 
Does your software graph the sensors output? I use Forscan and if you log live data using the oscillisocpe view you can then graph a WOT hit on throttle to see if the O2's are operating the same bank to bank. Check out Scanner Danner who does the WOT check to see if a Cat is plugged.
www.scannerdanner.com

02 sensor full throttle test /on road test

02 sensor full throttle test /on road test
www.scannerdanner.com www.scannerdanner.com
 
Torque outputs in csv, I dump the data into excel to graph it.
 
Generalee0527 said:
Does your software graph the sensors output? I use Forscan and if you log live data using the oscillisocpe view you can then graph a WOT hit on throttle to see if the O2's are operating the same bank to bank. Check out Scanner Danner who does the WOT check to see if a Cat is plugged.
www.scannerdanner.com

02 sensor full throttle test /on road test

02 sensor full throttle test /on road test
www.scannerdanner.com www.scannerdanner.com
Click to expand...
For the record, that's not what I said. It's likely getting heater voltage. you have to check from the heater to the signal.
 
With a narrowband O2, you can cross-reference the voltage with the STFT to see if they're close.

When the O2 voltage is over 1V it means a rich mixture; under 1V means it's lean. In terms of STFT, that should mean an STFT under 1 corresponds to an O2 voltage over 1, and vise versa.
 
Here's some of the O2 / FT data:
Bank 1Bank2
O2FTO2FT
For 32s straight, no switching
0.12​
0​
0.085​
2.34375​
Max O2:
0.975​
10.15625​
0.975​
10.9375​
Min O2:
0.1​
3.125​
0.1​
1.5625​
For another 33s stretch
0.78​
-0.78125​
0.755​
-1.5625​
Max FT:Sample of a data stream when FT2 is maxed out:
0.255​
25​
0.02​
42.1875​
0.02​
42.1875​
0.04​
42.1875​
0.03​
42.1875​
0.03​
42.1875​
0.135​
42.1875​
0.215​
42.1875​
0.305​
42.1875​
0.165​
42.1875​
0.165​
42.1875​
0.14​
42.1875​
0.015​
42.1875​
0.195​
42.1875​
0.195​
42.1875​
0.09​
42.1875​
0.09​
42.1875​
0.015​
42.1875​
Min FT:
0.77​
-13.2813​
0.71​
-8.59375​

It doesn't seem to be inversely proportional like you say.
 
Something is fucked. There's no source for 42 V in the car. if it reads outside 12V, its the software. I've never seen anything like that with my xcal2.
 
Grog6 said:
Something is fucked. There's no source for 42 V in the car. if it reads outside 12V, its the software. I've never seen anything like that with my xcal2.
Click to expand...
42 is the STFT, not a voltage.

But I do agree something is F'd.
 
If I'm reading that right, it starts off in open loop correctly (no switching) then when it goes into closed loop. Your data sample shows it dumping fuel, but the O2s show a lean mixture (voltage close to 0).

I'm not a Torque user so I'm not sure what a fuel trim of 42 actually means. Maybe it's a combined fuel trim showing the overall fuel correction after adaptive scaling of the lambda? E.g. 42% enrichment of fuel delivery over what the MAF says the car needs?

What happens if you disconnect the MAF?
 
Those sections of not switching are after the truck has been running a while, so it sounds like it's going into open loop even after being warm. That happens intermittently throughout drives.

The fuel trim value is Short Term Fuel Trim %.
 
Last edited:
Ultimately she idles like crap, RPMs up & down with the MAF unplugged. Looking over the data now.

O2 B2S1 was not responding this whole time and STFT quickly ramped up to max ~42%.

About 1.5 min after the MAF was plugged back in the O2 voltage climbed to max 0.8399; the STFT2 dropped to 21.875% and stayed there till I shut down. Engine temp was 165 at start up, I had ran to the store a few minutes earlier.
 
Last edited:
Here's some data from the MAF disconnect experiment:
Mass Air Flow Rate(g/s)O2 Bank 2 Sensor 1 Voltage(V)Fuel Trim Bank 2 Short Term(%)
6.69999981​
0​
42.1875​
0​
0​
42.1875​
0​
0​
42.1875​
0​
0.11​
42.1875​
One minute later; I had rev'd the engine at this point
0​
0.72500002​
5.46875​
0​
0.73000002​
0​
0​
0.76999998​
-3.125​
0​
0.67000002​
-7.8125​
0​
0.685​
-7.8125​
0​
0.685​
-10.9375​
0​
0.13500001​
-7.03125​
9.18000031​
0.08​
-2.34375​
9.18000031​
0.1​
0.78125​
6.11999989​
0.075​
7.03125​
9.44999981​
0.075​
7.03125​
9.13000011​
0.075​
10.9375​
9.13000011​
0.095​
17.1875​
8.97000027​
0.07​
17.1875​
8.76000023​
0.07​
24.21875​
8.55000019​
0.075​
30.46875​
8.55000019​
0.085​
39.0625​
8.28999996​
0.07​
39.0625​
8.02000046​
0.07​
42.1875​
8.02000046​
0.075​
42.1875​
 
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