I have a standard Actron OBD-II reader but I wanted something that was reasonably priced and not huge. So I decided on the U-Scan and I am happy with it. It does live view of data and you can save logs, etc. I also paid for some extras in the App but overall the price was under $75.00 still.

http://actron.com/uscan/ I got it on Amazon Prime.

Here are some screen shots of it. It is way better than the Cobb in terms of the data that can been seen. I am still trying to figure what exactly a couple of things are.

http://www.flickr.com/photos/9krpmrx8/9965360873/http://www.flickr.com/photos/9krpmrx8/9965297986/http://www.flickr.com/photos/9krpmrx8/9965366793/http://www.flickr.com/photos/9krpmrx8/9965270204/http://www.flickr.com/photos/9krpmrx8/9965270204/http://www.flickr.com/photos/9krpmrx8/9968396953/http://www.flickr.com/photos/9krpmrx8/9968290624/

 

My fuel system status is weird, on this it reads CL-Fault and on my Good Box it reads CL-Error at idle. The Cat temp is interesting too since I don't have a cat So I guess I can use my primary O2 as an EGT gauge? It's interesting that it tracks mileage too.

 

be aware that you cannot use this with any other piece of software. i.e. those of us that love torque and it's feature set will not be able to use it with this device.

 

I have suspected that the reported cat temp is calculated from one of the two O2 heater circuits. They aren't full 12v all the time, they pulse with logic, so I have to believe that there is some sort of feedback that allows it to know what the temp of the sensor is, and I'd theorize that you can backwards calculate the EGTs from how much you have to heat it.

I'd also guess that it would use the rear O2 for this, but it could be either one and/or both.

 

OBD2 catalyst temp is read from the rear o2 sensor. The way that the o2 sensors plot their measurements is voltage over temperature. Based on the circuit temp, and the output voltage, the ECU determines if the reading is rich/lean/stoich. That is what makes 'fooling' these so difficult . Btw, IIRC, although the input voltage of the sensors are 12V+, the output voltage ranges between 0 - 5v

 

Also, i forget what the different fuel system statuses are, I need to take a look at my notes at home, but they cover a range of possible modes:

If i remember correctly:
CL - O2 Source
CL - Using O2 Source, Feedback Fault
OL - Deceleration / Load
OL - System Failure

 

Okay, now here is the monkey wrench. I have no rear O2 in the exhaust stream. It is plugged in but it is zip tied to the transmission. My aftermarket O2 is in the stock secondary location.

 

It can only mean that it's using the front O2 source. Could be a backup method for determining it, like "if the rear o2 isn't responding use the front". Our ECU is smart enough it wouldn't surprise me at all.

 

Ah, thats why you are getting the closed loop error.

There is a fuel system status that has "Closed loop, but fault with at least one oxygen sensor." So year it may default to the other "working" one

Now again, these are just generic SAE OBD2 codes, so they are usually worded poorly. But you have no fuel system issues with the rear o2 outside of the exhaust stream? Typically the car would stay open loop until the o2 sensors are up to temp

 

It's goes to open loop without an error. But yeah you are right, the error may be caused by that. I have extra O2 bung, I have just been lazy.

 

let me double check to see what mine reports back as a value. again, an SAE standard, but our ECU's may just play some games on idle

 

i wouldn't use Cat temp for tuning too much, as its a value that comes from how hot the O2 sensor is, and we don't know if the O2 temp is literally what it says, or they took the o2 heater voltage and indexed it to cat temp.

ideally you'd want it to stay around stock values.

 

Yeah I wouldn't use it for tuning, I don't tune my car anymore , more just to pay attention to how hot EGT's are.