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

[jimmy57]

The rear sensor will go to its rich and lean extremes when there is load change on engine. <0.1 v when you let off throttle and >.75 v when you get into throttle or pull hills or other high load situations. When you are at steady load the rear sensor should be between 0.65 to 0.75 V. Idle is not important, you need to see what it does on level ground at steady throttle.

The wide band style sensor used in front of cat is shown as lambda where <1.0 is rich and >1.0 is lean. when lambda is between 0.97 to 1.03 and cycling that is as expected.

[quietcoolone]

Looking at voltages the first one seems to be for rear sensor and second for last, correct? The second voltage level is way low so I'd look into connectors and harness condition. With meter plugged in have someone wiggle wiring around to see if volt level changes.

According to VIDA 0.85 for rear sensor, and 1.01 for the front but there is no unit of measure so i don't know what it represents. I did borrow a cheap scanner that does live data and i get the following:
at 2481 RPM | 655RPM) (idle)
SHRTFT1(%) -2.3 | -3.9
LONGFT1(%) 0.0 | 0.0
O2B1S2(V) 0.700 | 0.625
O2S11(mA) 0.039 | 0.051
ECT (F) 188 | 188
RPM (rpm) 2481 | 655

note that the this scanner measures the current on the front sensor (O2S11) in mA but i could not find a Voltage reading for that sensor.
I ordered Actron CP9580 scanner that measures voltage on both sensors and at will post those numbers when i get.

i'm still getting ECM-4801 , Bank 1 -faulty signal
I also took temperature readings on the CAT:
preCAT: 200F
postCAT: 340F
which seems to indicate the CAT is working but still need to resolve this CEL.

Thanks again

[jimmy57]

Rear sensor is binary type where the output is shown by VIDA as Voltage.
Front is wide band type where the calibration V and the signal V are related in order to determine the rich or lean of mixture to a much greater precision than binary sensors. Since the correlation of calibration and signal V must be done to get the info it is presented by VIDA as lambda. Lambda is effectively an expression of stoichiometric attainment with >1 representing excess oxygen (too little fuel) and <1 representing too little oxygen (too much fuel).
The catalyst should be using the slight extra O2 of stoichiometric combustion in the catalyst process and that results in a reduced oxygen content post catalyst that makes for the desired post-cat range that is "rich". For binary sensors <0.5V is lean and >0.5V is rich

[draser]

The first sensor is a wide band type which generates a continuous signal (volts) proportionate to how rich/lean mixture is. The rear one is your regular narrow band which switches back/forth which yours does. The problem that I'm seeing if I read your results correctly is the extremely low voltage out of sensor one. Can you 2-check to make sure you have the correct type?

[draser]

One more thing: you can use Torque to read the A/F ratio which should be your indicator of sensor 1 operation - on my car it reads 14.7 which is called stoichiometric ratio, at idle engine hot.

[quietcoolone]

One more thing: you can use Torque to read the A/F ratio which should be your indicator of sensor 1 operation - on my car it reads 14.7 which is called stoichiometric ratio, at idle engine hot.

Thanks for the additional help. I don't see a Torque option in Vida (i just realize Torque is an app)
Is there anything else i can check for you to evaluate?

Thanks

[draser]

Not familiar with Vida but I'd hope it has capabilty to read AFR, perhaps someone can jump in to help. Can you check to see if the heater of sensor 1 has power? Should be an easy read at connector.

[jimmy57]

The front sensor display is not voltage on that model. Wide band sensors output voltage has a small range of usually less than 100mV and the level of the voltage varies a great amount car to car. The ECM will compare the reference control signal and the signal out to give the display value that VIDA calls lambda and has no unit associated with it. Monitoring voltage of wideband style makes little sense and can't be specified readily as rich and lean so the display of it will be lambda. A direct read of oxygen reference chamber or calibration signal and output by using voltmeter between these two will yield a low millivolt signal that swaps polarity as the out ranges above and below the calibration voltage.
Rear sensor sweeping as binary front sensors do indicates faulty cat if the load is stable. The oxygen level in and out of cat should change with little oxygen remaining if catalyst is functioning. On acceleration the post-cat sensor will show rich (>.75V) as catalyst function diminishes when low oxygen exhaust from extra fueling puts component gas levels in exhaust of range needed for catalyst function. Coasting brings injector fuel delivery stop until engine gets down close to idle speed so the engine is pumping oxygen to catalyst and post cat sensor will register high oxygen content (nearly 0 V). When the load is stable the front sensor will oscillate about stoichiometric, in the case of wideband this means .97 to 1.03. When the front exhaust gas is deviating from stoichiometric in a small range then the catalyst will function well and the oxygen post catalyst will be low leading to the .65-.75 V that should be seen on rear binary sensor.

If power supply is missing for the O2 sensor there would be a code and check engine light. The ECM does amperage monitoring of the heater in order to determine the pulse signal used to keep sensor heat at desired level. When there is no current draw the ECM knows it and sets code.

Back to original problem: 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. 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. The speed of the response to throttle apply and release is important. More than 2 seconds would not be good. 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.

[quietcoolone]

Back to original problem: 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. 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. The speed of the response to throttle apply and release is important. More than 2 seconds would not be good. 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.

Thank you both.
Jimmy,
i will hook up VIDA and take a run tomorrow and post my results here.
Just one question:
When you say, 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
those number for the front sensor are lambda not voltage correct? (just as displayed in VIDA)

Thanks

[draser]

I guess it depends on what one uses to measure the sensor output - as seen in this training material:
http://wps.prenhall.com/chet_halderman_aepd_5/
It seems that manuf.and common obd2 readers display volts, just as my Torque app shows AF ratios and Vida I learned shows lambda ratios.