Hi,
Purchased an 04 S60 2.5T about a year ago and the check engine light was on for multiple faults including transmission. Fortunately all but one code remain (car now has 122K miles)
ECM-4801 Three way catalytic converter efficiency, bank 1 faulty signal.
Back in March i replaced the Front 02 sensor (Bosh 28851171373), cleared the cel but it returned.
I've cleaned the TB, MAF sensor, replaced plugs and coils, new gas cap rubber seal, cleared the cel but within a few days it was back.
Last week i replaced the downstream 02 sensor (Bosh 28851164887), cleared the code, resent ECM but the cel is back on.
I've searched the forums for help but most seem to point to a bad catalytic converter. I can't tell if the cat is bad but there is no smell or smoke. The car averages 25 gal city, and 30 hway. (93 octane)
i connected VIDA to graph sensor waveforms (take a look at the pictures).
It is my understanding that sensor 1 is upstream (before cat) and senor 2 is downstream (after cat) and the computer uses the upstream sensor to gauge the air/fuel mixture.
Based on VIDA, upstream sensor shows very little or no waveform (straight line), and downstream sensor has constant waveform. Is this in reverse?
Notice the upstream sensor produces a waveform as i release the gas pedal (See picture 2 & 3), otherwise its basically a straight line.
Picture 4 -- results from disconnecting intake manifold vacuum hose, and picture 5 is with hose reconnected.
I hope the pictures provides a better understanding of what I'm dealing with and perhaps someone can shed some light and help me get this issues resolved. The car is going in for state inspection by the end of next month.
Thanks in advance

 

your front sensor should be switching from 0.1-0.8v, and the second sensor should be fixed more or less at 0.6 (which is lambda 1, where it's polluting the least)
so from the pictures it looks like the front sensor is bad.

 

Thanks for the input.
I also thought of that but:
1. The sensor is less than a year old (march 2014).
2. Unlike the Rear sensor (4 wires) the Wideband front sensor (5 wires) display in Vida is not voltage.
I also hooked up a OBDII Scanner to them and it displays current for Front and Voltage for Rear, so based on that i'm not able to determine if the sensor is bad.

any ideas?

 

Old thread but the quick and dirty way to check your catalytic converter is to measure the heat before and after it - but you must rly get the cat hot first - temp before cat should be around 200°F = 90+°C and after the cat around 400°F = 200°C