I've figured out how to finally get my scanner to record live data and copy it to my PC. Now I'm trying to figure out how to make sense of it and if it points to any culprits in my search on how to fix my P0420 CEL. Any help or insight is GREATLY Appreciated !

Below is a small excerpt of the log file:


Live Data
Number of DTCs stored in this ECU 1
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated LOAD Value(%)18.0
Engine Coolant Temperature(¡£C)199
Short Term Fuel Trim -Bank 1(%)-0.8
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)0.0
Long Term Fuel Trim - Bank 2(%)-0.8
Fuel Rail Pressure(gauge)(kPa)54.8
Intake Manifold Absolute Pressure(kPa)4.9
Engine RPM(rpm) 709
Vehicle Speed Sensor(km/h)0
Ignition Timing Advanece for #1 Cylinder(¡£)8.0
Intake Air Temperature(¡£C)141
Air Flow Rate from Mass Air Flow(g/s)0.01
Absolute Throttle Position(%)3.5
Location of Oxygen SensorsB1S12--B2S12--
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.095
Short Term Fuel Trim Bank 1-Sensor 2(%)0.0
Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.275
Short Term Fuel Trim Bank 2-Sensor 2(%)0.0
OBD requirements to which vehicle is designedOBD&OBDII
Distance Travelled While MIL is Activated(Km)402
Equivalence Ratio (lambda)(Bank 1-Sensor 1)0.999
Oxygen Sensor Current(Bank 1-Sensor 1)(mA)0.148
Equivalence Ratio (lambda)(Bank 2-Sensor 1)1.003
Oxygen Sensor Current(Bank 2-Sensor 1)(mA)0.000
----------------------
Number of DTCs stored in this ECU 1
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated LOAD Value(%)18.0
Engine Coolant Temperature(¡£C)199
Short Term Fuel Trim -Bank 1(%)-0.8
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)0.0
Long Term Fuel Trim - Bank 2(%)-0.8
Fuel Rail Pressure(gauge)(kPa)54.8
Intake Manifold Absolute Pressure(kPa)4.9
Engine RPM(rpm) 716
Vehicle Speed Sensor(km/h)0
Ignition Timing Advanece for #1 Cylinder(¡£)7.5
Intake Air Temperature(¡£C)141
Air Flow Rate from Mass Air Flow(g/s)0.01
Absolute Throttle Position(%)3.5
Location of Oxygen SensorsB1S12--B2S12--
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.175
Short Term Fuel Trim Bank 1-Sensor 2(%)0.0
Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.120
Short Term Fuel Trim Bank 2-Sensor 2(%)0.0
OBD requirements to which vehicle is designedOBD&OBDII
Distance Travelled While MIL is Activated(Km)402
Equivalence Ratio (lambda)(Bank 1-Sensor 1)0.995
Oxygen Sensor Current(Bank 1-Sensor 1)(mA)0.051
Equivalence Ratio (lambda)(Bank 2-Sensor 1)1.006
Oxygen Sensor Current(Bank 2-Sensor 1)(mA)0.051

 

You don't mention the time frame for the data but I would guess maybe once per second. I notice some mis-shaped blocks in the file. Also I don't see any clear field separators. Those would make it difficult to import the data into and excel file. As an excel file you could scroll and watch for varying or unexpected values of your sensors.

Are there other output types available? Cleaning up malformatted data can be time consuming, and if you can't trust the formatting, can you trust the data?

 

I'm going to try parsing the data and checking if I can use a line break as a delimiter for .csv file. Not sure what the frequency is for the interval recordings, but did notice that towards the end of the capture the data starts to looses some of the line breaks and gets 'dirty'. I'm going to try focusing on the first 10-15 blocks and repost. Thx

 

Bank 2 sensor 1 looks funny for idle...

 

myexcusion, I had p0420 and replaced the o2 sensor. The lower one between the engine and the firewall. I never removed the manifold which made it more of a pain to get to but I managed. About a week later p0420 come up again. I then removed the new sensor and put an o2 extender oxygen sensor spacer on first. This has been over a year ago and I have never had p0420 since. O2 spacer was only about $6.00.

 

I was thinking of a spacer too, but don't think it'll work in NY.

 

I took the log file and tried separating it out into columns as best as I could. Hope this helps make it easier to read and see what may look out of place or not.

Thanks

 

I would check on that if I were you. As far as I know, NY emission only check with OBDII, (to make sure CEL is working.)

 

I think you're right - it's OBDii only. Do you have a link to the spacers you'd recommend ? May give them a shot.

I'm still trying to decipher the .xls log file too

 

really ? i'm trying to figure out what exactly I'm looking for...

 

O2 Extender Oxygen Sensor Spacer HHO Test Pipe 1 Bung | eBay This is what I used.

 

Why isn't it just a bad cat, as the code suggests?

 

P0420 does not necessarily mean bad cat.

 

Ordered the one above and will give it a shot.. worth trying for 5 bucks in the meantime and see if it helps

 

If it does work for you, spend a few extra dollars and grab a stainless steel spacer, and don't forget to put anti-seize compounds on the threads!

 

BY THE WAY -- I'm assuming this spacer is for the S2 ( Sensor 2 ) downstream post cat converter - right ?

 

Correct. The front sensors are actually air/fuel sensors that can't be spaced without making the computer think that the car is running lean and dumping fuel in to richen it up, which WILL trash a cat, the lower is just looking to see how efficient the cat is.


Apparently, the program is extraordinarily sensitive on our cars, and the CEL is trip at 97%.


Most high-end cars won't even go 'pending' until 95%, nor throw a CEL until 90-93%.


This allows for letting off the throttle quickly, which sensors will see as lean, and sniff as low efficiency. It IS low efficiency, but only for a few moments.


On the Rover, LR actually remapped the function to reduce the unnecessary warning lights. Looks like Jag never did. Oddly, the Mondeo, with almost the same computer, never through the codes like this, they use the standard Ford mapping.

 

True but all your data suggest a bad cat. What have you done to rule that out?

 

That's what I'm trying to figure out and posting the datalog file If someone understands the log file data they may be able to interpret it and see if the cats are doing their job, or if it's a bad o2 sensor, or vac leak etc...

I do know that there is no foul smell, smoke, hesitation, stumble or crackling sounds coming from the exhaust , so before spending thousands on new cats - i want to be 100% sure it's not anything else... cats are a last resort if everything else points to them ( and the spacer doesn't work ).

 

I see those numbers, and they scream bad lower sensor.


The surest test is a tailpipe sniffer, find out what the exhaust actually is.


I was sure I had bad cats, had them sniffed yesterday, and not only are the cats OK, they are better than some new cars, and had been replace with new factory cats sometime in the car's past.


Realistically, a cat should last the life of a reasonably maintained car, especially the factory cats on these things, they are put together very well with a solid honeycomb and a lot of precious metal.


Replacements can be had for reasonable dollars (about $300 for the pair), but they don't have nearly the guts that the originals do.


The front sensors actually look at the fuel/air going in and coming out of the combustion chambers, and if they sense too many hydrocarbons (or not enough) coming out, they will tell the computer to richen or lean the mixture to get the exhaust into expected parameters (fuel trim).


These numbers say that the mixture is as expected.


The back sensors are after the cats, and they sense the ratio of several gases in the exhaust, and if they are 'too high', they decide that the cat is not efficient and throw a code.


Now, our Jags use a high-temperature sensor (like 600º C!) that has a heater to bring the sensor up to temp quick.


The Jag's computer is based on that rapid change.


The heaters actually burn out, meaning that the sensor is still OK, but the changes aren't fast enough. The car still runs as it should, but the CEL comes on because the car decides that the cat is inefficient. In reality, there is nothing wrong with the cat. If the actual front sensor fails, by the way, the trim goes crazy, and the computer will start dumping all kinds of extra fuel into the system, but at that point, you will have a LOT of codes to deal with (and a blinking CEL). Too rich a mixture will damage a cat quickly, and if too much fuel gets into the cat, it can light off in the convertor. That is an expensive backfire, because it will fracture the honeycomb, an the cat will truly be trash at that point.


Denso, the manufacturer of out sensors, considers them a consumable part, and they actually have an 'official' life expectancy of only 30,000 miles in the Jag application. This considers 50/50 highway/city driving.


Again, in reality, the MTBF (mean time before failure), sort of wrong, since they are more 'mileage' based than 'hour' based is around 100,000 miles.


However, here we are 6 to 12 years out, throwing codes like dice in a craps game.


That is why it is rarely the cats, and more often the sensors.


Jag's own DTC tree indicates this; there is an entire list of things to check before the cats.


The 'cheater' gets the sensor tip out of the exhaust stream, so it thinks that all is OK. The downside is that if something does go south, you will lose that warning early on.