2004 S60 ECM-4801 Cat. Faulty Signal. includes waveform

[quietcoolone]

Hooked up my laptop/VIDA and went out on the road today and these are my findings:

The rear sensor should be monitored while driving at a constant speed on level road to see if the signal settles in a range of .65 to .75 V with only small ranging within those limits.
Rear sensor settled (for the most part) around 0.73V (cruising on level hwy @ 65MPH)

If the front goes below .95, even as low as .75, on hard acceleration and then over 1, even as much as 2 on immediate coast then front would be doing as it should.
On hard acceleration the front sensor read between 1.00 and 1.03 and on immediate coast jumped and held at 5

The speed of the response to throttle apply and release is important. More than 2 seconds would not be good.
Response time was good (fast).

The rear sensor should go over .75V on hard acceleration and fall below .1V on immediate coast then it is doing as it should. Again the time to register change should be under 2 seconds. It is actually a faster response than that but lag time for scan tool adds a second or more.
On hard acceleration the rear sensor was normal (.75V or little higher) and fell to 0V on immediate cost with good response time.

I also found this test recommended by jimmy to another member:
A high miler car (150K and up) is suspect for a worn out cat. Faulty sensor (usually front) can also be a cause. Sensors can be evaluated with a good level of thrust by watching readings on scan tool for front if wideband sensor (99 up Volvos) and either scan tool or direct for rear. Engine at normal op temp, create a vacuum leak 1/8 inch hole size or a bit larger. Watch the scan tool when the leak is created. The oxygen sensor should respond to lean (wideband lambda value >1, binary voltage < 0.5V) within 2 seconds. After the leak is present for 2-3 minutes then plug leak and watch for rich indication (wideband Lambda <1, binary voltage > 0.5V).
My results are:
Engine at normal op temperature:
Front 1.01
Rear 0.73V
MAF 9.9 Kg/h
RPM 640
With vacuum hose removed:
Front 1.82 leveling off at 1.10
Rear 0.02V leveling off at 0.05V
MAF 12Kg/h leveling off at 13.8
RPM 600 slowly increasing to 1120
vacuum hose back on:
Front 0.80 slowly increasing to 1.01
Rear 0.82V slowly decreasing to 0.72
MAF 13.8Kg/h slowly decreasing to 9.9Kg/h
RPM 640 and holding

To me something is not right with the Front Sensor and likely why the ECM-4801 refers to it as "Faulty signal"

*leveling off is the period (about a min) between rough and normal idle

[draser]

I see the sensors change as mixture changes, why do you suspect sensor 1? Also, can you look at your fuel trims?

[draser]

These tests show that the sensors indeed follow the mixture change, however some steady state data is required to understand what's setting your fault. And that is lambda values for part throttle, say keeping rpm at 2500 to get to 60 and then lambda at cruising speed. These are the actual conditions that would set your fault. The fuel trims now may provide additional info on an existing rich or lean condition, and looking at your gas mileage I'd look for lean. As for your bad signal message, again wiring and sensor 1 connector need looked at.

[quietcoolone]

These tests show that the sensors indeed follow the mixture change, however some steady state data is required to understand what's setting your fault. And that is lambda values for part throttle, say keeping rpm at 2500 to get to 60 and then lambda at cruising speed. These are the actual conditions that would set your fault. The fuel trims now may provide additional info on an existing rich or lean condition, and looking at your gas mileage I'd look for lean. As for your bad signal message, again wiring and sensor 1 connector need looked at.

i took some pictures last week that include fuel trim, RPM and sensor data :
SHRTFT (%) -0.8
LONGFT (%) 0.0
O2B1S2(V) 0.74
O2S11(mA) -0.016
RPM 649

SHRTFT (%) -0.8
LONGFT (%) 0.0
O2B1S2(V) 0.12
O2S11(mA) -0.036
RPM 2265

SHRTFT (%) -2.3
LONGFT (%) 0.0
O2B1S2(V) 0.73
O2S11(mA) 0.031
RPM 2405

SHRTFT (%) -3.9
LONGFT (%) 0.0
O2B1S2(V) 0.65
O2S11(mA) 0.008
RPM 2449

SHRTFT (%) 0.8
LONGFT (%) -0.8
O2B1S2(V) 0.400
O2S11(mA) 0.008
RPM 653

SHRTFT (%) -1.6
LONGFT (%) -0.8
O2B1S2(V) 0.625
O2S11(mA) -0.008
RPM 2550

SHRTFT (%) -4.7
LONGFT (%) - 0.8
O2B1S2(V) 0.310
O2S11(mA) 0.07
RPM 2623

Freeze Frame Data
DTCFRZF P0420
FUELSYS1 CL
ECT (F) 188
SHRTFT1 (%) -2.3
LONGFT1(%) 0.0
RPM 2160
VSS (MPH) 68
TP(%) 18.0
MAF (Lb/s) 0.04

I disconnected both sensors and cleaned contacts before reconnecting. In this car is is difficult to get to the sensors but i manage by laying atop the engine and disconnecting the turbo flex pipe from the air box.
I don't know if i got a bad front sensor but both were replaced, cats temperature seems normal (hot at the front, 100 degrees cooler at the rear.
My next step is to remove the ECM and test for continuity but before i do i'm going to try to find a wiring diagram.
About mileage, are you saying i should get better gas mileage if in fact its running lean?
The car averages 25 gal city, and 30 hway. (93 octane)

Thanks again for trying to help.

[draser]

Fuel trims are normal, low single digits, indicative of no air leaks, good combustion, etc. Gas mileage is great so the cat is not plugged. As for cat chemical efficiency one indicator is rear sensor switching less than front, about 7/10 respectively. Not sure Vida can capture that.

[draser]

Here are 2 snapshots of front and rear o2 sensors. Looking at the time scale I count about 10 sec for sensor 1 and 12 for sensor 2, which is complying with the 2 sec rule that sensor 2 switches less than 1. That tells me the cat does it's job. Engine load was about 25% at 50mph steady to indicate cat flow. Hope this helps.

[draser]

Screenshots are reversed, first is for 2.

[quietcoolone]

that is pretty much the waveform of my my front sensor (can only measure current)
The voltage and waveform on rear sensor is not as steady as it should.
I've added a "spark plug fouler" to the rear sensor (Dorman 42009), cleared the code and driven the past 13 days (500+ miles) without the CEL (it would usually come back between 50-75 miles).
This band aid fix tells me that the cat is dirty, poisoned and fallen out of spec with the ECM and right now i can't afford a new catalyst.
What are your thoughts?

[jimmy57]

What is missing here is the ECM info on the various times it is monitoring for catalyst performance other than steady load cruising. I have had many vehicles with catalyst codes that would set codes on throttle release based on viewing the frozen data (low throttle but high road speed as in reducing throttle once you have crested a hill) and others that would detect the fault idling.
I have an aftermarket low restriction catalyst on my R and it is not a great performing catalyst based on oxygen sensor signal monitoring alone but the ECM is happy with it and has never set any catalyst codes.
When your cleared the code(s) on your car was there a pattern to when the light would come again?

[draser]

If you partially take the second sensor out of the flow that will probably lower switching frequency, hence no fault code trigerred. Sounds like a cat...