No one has mentioned rear O2 sensors. It is my understanding that P1174, "Catalyst Inefficient," is based on the data from the rear oxygen sensors. The original poster reported that he changed the front O2 sensors, but never mentioned the rears. Maybe he just needs new rear oxygen sensors. In other words, the cats work fine, but the ECU believes they do not based on data from faulty rear O2 sensors.

 

The job of the rear 02 sensors is to notify you that your cats are not doing their job. That is what the OP's rear 02 is doing. The only way to know for sure, is to read the live data of the rear 02's, should be a steady voltage.

 

Glad to see that my thread finally got off Mikes condescending response and back to my question. Frank4 was the only one to notice Mike's incorrect statement, and even though he posted it, Mike did not acknowledge it. Ive seen Mike come and go, and having owned 5 Land Rovers now,....I am no stranger to this site, or Mike's mood swings. I have received some helpful information from Mike over the years, and this is not the first time he has been condescending. What Mike mis-stated was that I had a flashing CEL, Frank4 was the only person who noted that I mentioned a flashing ODOMETER, as my reason for only being able to estimate total mileage on the truck. while you guys have all been talking about Mike,...Ive been taking care of other fish. New Airbags, brakes, and navigation screen on my X5, refinishing the interior on my SLK, and sorting out an HID headlight issue on my 330ci,....and trying to get the two wheeled BMW out for a group ride on weekends. So, there is no end to vehicles needing attention.

I ran a service department for a Mercedes Nissan Dealer years ago, and owned my own European Restoration business for 20 years, so, I am no stranger to working on vehicles, and have owned over 100 cars, and 60 motorcycles, 40 of which were BMWs. I always do my own work, unless a vehicle is still under warranty or it's beyond the abilities of my home garage.

Getting my thread back on track,.....I was inquiring about best bang for the buck converters as I am fairly certain due to the codes I have been pulling repeatedly, that I have failing cat on one side (if not both). The truck is burning oil at the rate of about a quart per thousand miles,...so, Im thinking this has perhaps contributed to the cat failure.

That said,....I would certainly be open to hearing that I have misinterpreted my codes, and that I do not need to replace my cat,as, I am 65 now and crawling under my vehicles gets a little tougher every year.

I have a state inspection coming up in 6 weeks, so, it's time I addressed this.

As always, thanks for any and all advice. BTW, I paid $850 for my 2003 Disco about 2 years ago. Straight body, newish tires, cold AC. Had to do the headliner of course, tried painting it first, didn't like it so recovered it in material I bought from a local upholstery shop, my first time to do a headliner,....and with all the stuff on this headliner,...with the rear air conditioning, it was quite a job., Ive also done the plug wires, intake manifold gaskets, valve cover gaskets, , radiator, fabbed up an upper coolant hose T, replaced the air intake heater which is leaking again, rebuilt both driveshafts, replaced the steerubg Center link, replaced the front brake rotors and pads, and oddly, had to replace the parking brake driveshaft brake drum.......it took me quite a while to determine that the drive line vibration I was feeling was a warped emergency brake drum. The truck came to me that way. Prior owner obviously drove it with the ebrake on until it warped.,...oh also replaced the two subwoofers in the tailgate, and have of course replaced a door lock actuator, surprisingly, I have yet to replace a window regulator yet,.....or fabricate window regulator slides as I have done on prior Discos.

That's all for now.
Brian

 

I just realized what alot of this thread was about; I just tuned into it. Not to beat a dead horse, but I would like to make one statement. I've only been here on here a short time and I noticed Disco Mike's pompous attitude right away. There's more than one person in the world that knows how to work on cars, including these, which frankly don't seem all that difficult. So for everyone out there, feel free to hit me up if you need advice, I promise to be courteous and help you as much as I can.

Anyway, to get back on track, are you sure you don't have a vacuum leak somewhere?

 

Not 100%,...but the engine doesn't have a higher than normal idle speed or a rough idle (either one sometimes indicating a vacuum leak depending on the car). Could a vacuum leak cause the codes I listed back early in the thread?

 

Motorhead I just checked my voltages on my O2 sensors. Hadnt driven the truck in several hours, but not a true cold start
as it had been driven earlier today.

My two downstream O2 sensors were reading a consistent .450 with one bumping to .455 for a half second every so often. after a few minutes of running. I noticed that all four of my O2 sensors were cycling from approximately .050 to .850 and doing so in a fairly regular or consistent manner.

My DTC light came on again yesterday after resetting it a few hundred miles ago. Only one code this time #1450 which comes up on my Actron scanner as "Manufacturer specific DTC"

Brian

 

A while back I had a vacuum leak, can't remember the code exactly and it was on a different vehicle but it pointed to O2 sensor (something about threshold). Car was running rough though which yours isn't. I'm not saying it can but was just throwing it out there as something to check before buying anything else. FWIW, I've had a code on my Honda for the last 9 years, but I don't have to get it inspected...

 

Vacuum leaks should show a P0171 or P0174 depending on which side.
I P0171 for a while and just replaced all the fuel injector o-rings.
Code is now gone.

Steve

 

1450 would be evap. loss system No? it prevent gas from evaporating out of your tank into the atmosphere. to big a leak and it will trip a code; have you replaced the filler cap??

 

Ok, so I'm not a certified ASE mechanic, but this sounds like an open loop vs. a closed loop situation with the O2's?? I could be completely wrong, but when your system goes into closed loop after running for a short time, your down stream 02's are telling you that your cats are bad with the fluctuating voltages. I'm not sure if voltage readings from 02's vary between open loop and closed loop? I haven't researched this. I guess if I was ASE patched, I would already know this...

I need to maybe read back on this thread, but didn't you write this engine is burning a quart of oil every thousand miles? If that's the case, your cats are probably toast....MO