O2 Sensor - Need monitoring advice

[Lymzilla]

I have a 2007 Dodge Charger Daytona and have recently added a CAI, 180 t-stat, headers, hi-flow cats, and catback. Also, of course, I have a Predator and installed the '93oct w/ CAI' tune.

I've been getting an error code 'O2 sensor in Bank 1 indicates Catalytic Converter below threshold'.

I'd like to monitor both O2 sensors to see if there's a problem with either of them. Also, I'd like to monitor any other items (timing, spark, knock/retard, fuel...) to determine if a bad O2 reading is messing up my performance/mileage. The smell from the tailpipes is 'very rich'.

Anyone from DiabloSport know what would be best PIDs to monitor?

Please Help,

Lymzilla

[jtfinklea]

I run catless and have turned off the rear o2 sensors. My exhaust smells a little rich too. No CEL's at all. I believe the PID's are o2-1/1, o2-1/2, o2-2/1 and o2-2/2. I have a 5.7 hemi and run with the EGR and MDS disabled. I just made a run from PA to Louisiana 1153 miles down got 27 MPG doing 65 and 70 MPH, on the return got 23 mpg doing 70 and 80 MPG running 93 Octane gas on 9r07 crom w/ 93OctaneCAI. Always monitor LT-KNK and ST-KNK, intake manifold temp and base spark cylinder 1 and RPM and MPH there are a few others but you get the picture. Also you are getting more air now and you should add more fuel if you are getting LT-KNK and in some cases ST-KNK. If the ST-KNK is at the shift point then that is normal and could be false knock. It is said that the knock sensors are very sensitive in these cars.

[Lymzilla]

My LT-KNK and ST-KNK seem to be fine. I'm getting no LT-KNK at all, and my ST-KNK only gets between 2-4 during WOT shifts, so I believe that is quite normal. If anything I'm more concerned that I may have too much gas in my exhaust, so that's why I want to monitor my O2 sensors to make sure they are OK. I also have just over 30k miles on the car, so I also wonder if the spark plugs are all doing their thing. Anything to get the most from my gas for HP/TQ and mileage.

[Quick]

The tune will not effect that in closed loop mode. Generally speaking the tune is only going to effect a/f and spark during WOT. Are you smelling too much gas at idle? haha, if not, I'd like to know how you're smelling your exhaust at WOT

If you're smelling too much gas at idle and closed loop mode I don't think monitoring your narrowbands is going to tell you much. Unless they're completely broken and pegged lean. If that's the case then I would expect it to throw other codes along with the Cat code. In closed loop the narrowbands are going to be cycling between almost 0v and almost 1v constantly (0.5v is about 14.7:1). I suppose if the narrowbands somehow got out of calibration then you might be getting 0.5v when the a/f is richer than 14.7:1. But I would still expect them to be cycling. The PCM would still be adding and subtracting fuel "hunting" for 14.7 but due to the bad sensor it would actually be shifted rich. That wouldn't look any different on the Predator monitoring the sensor.

Now if the sensor is just pegged lean I would expect the PCM to recognize that and maybe use a fuel setting thats guaranteed safely rich. You would be able to see that but I would expect some serious codes along with that condition.

You really need to check it with a wideband sensor. Maybe you could go to an emissions check station (or something like a AAA garage) and see if they could check it. That would be cheaper than a dyno. Of course with a dyno you would have the added benefit of seeing what kind of horsepower you're putting to the ground

[Lymzilla]

Thanks for the detailed analysis Quick. Funny thing is I bought the wideband sensor, had the bung installed, but I haven't wired it all in yet. I'll have to get by without it for now. For now I'm just trying to check that my O2 sensors are working, the fuel is being properly delivered, and the spark is occurring at the right time. I'll post my findings if I find anything 'funny' going on.

[Lymzilla]

Well, I monitored the O2 (narrowband) sensors and all 4 of them are varying between 0v and 1v as Quick said they should. So this must mean that the sensors are 'working' (not burnt out).

I'm still not sure what else to monitor to see if there is anything 'funny' going on that might make my engine run richer than it should. I don't want to 'lean' out the fuel or anything else until I get my wideband sensor/guage installed. I am still running the '93oct w/ CAI' tune (yes - I have a CAI).

[Quick]

I suppose you could monitor the injectors pulse width (does the predator do that?) and compare it with the specs. You'd know it if a cylinder wasn't firing, it's not that. What does Cat Below Threshold mean anyway? What threshold? Is it possible your cats are dead?

Whats the spark timing? If it's way retarded you're not going to get a full burn... I think your easiest option at this point is get a wideband on it.