Hello all. I have conducted a search but have been unable to find the info required. Can someone advise on upper/lower signal wire voltage thresholds that would cause a CEL for Post Cat sensors. What is the lowest voltage and what is the highest voltage required to give CEL. What voltage should I see for a good system. I have just installed new Bosch post cat sensors and have a CEL 0422/0432 Threshold codes. Thinking I may have a bit to much extension between sensor and exhaust temp/flow? Aftermarket cats installed. 90degree and 2" extension that only has small hole. I have removed the 2" extension but have not driven yet. Yes I have an oscillator scope. TIA
Would I be correct in saying that these sensors would be Narrow band? So anything oscillating between .2 and .8 volt should not cause a CEL
Yes, the O2 sensors are narrow band. Oscillation 0.2 to 0.8 volt of the pre-cat sensors is normal but not for the post-cat sensors as they should have a small oscillation. Also see this thread: https://www.ferrarichat.com/forum/threads/355-5-2-obd-codes-0422-0432-0153-1121.634333/
Just driven about 130ks no CEL Will check for pending codes tomorrow after work. Moving the sensor a bit closer to the exhaust may have helped
Are your new Bosch post-cat sensors universal/generic or Ferrari OE/OEM? Using universal O2 sensors as post-cat can create quite a bit of a problem (I think that's why the original ones are so expensive, hard to replace with universal). The original post-cat sensors have considerably stronger heaters so, if your new sensors are universal (weaker heaters), they were probably running too "cold" with you original installation further away from the exhaust. After you have moved them closer (hotter), they will hopefully work well.
Bosch #15738(should be the same heater?) I had new plugs to install instead of using old ones. I only have the 90°bend extension. My cats only seem to get to around 235c(450f) at the post cat sensor area. I couldn't help myself to check codes. Pass and pending codes Pass None detected
Bosch 15738 is a universal sensor but if it now works, leave it there. Perhaps you can check its heater resistance when cold. According to the measurements taken by Ian (that he provided in the other thread), the pre-cat's heater reads 3.3 Ohm and the post-cat's 2.0 Ohm. You can also take the reading on your old post-cat (if original) and compare. Since you have an oscilloscope, perhaps you can hook it up and see the shape of the signal from the new post-cat. If fairly flat (at idle), your positioning is good.
The signal scan would need to be done in closed loop(run temp) Correct? And lower resistance would mean higher heating? Thanks for your help much appreciated
Yes, the engine has to be in closed loop in order to be able to correctly measure the signal. Check the signal at idle first, then you can also see how it changes at some moderate revs. The curve will move up at revs but should stay relatively flat (smooth). Resistance of 2.0 Ohm, vs. 3.3 Ohm, means considerably stronger heater.
Precat heater 2.3 ohms resistance Closed loop sensor voltage .36 to .48 steady but get the occasional .68(very random) still pretty steady at 2000rpm. Occasional little spike
