Hi there folks - dumb *** here.
I changed the plugs and wires and accidentally crossed two of the wires. It was late and I couldn't isolate the problem (since my sharpie marks rubbed off the boots) so I drove it to my local shop 5 miles away. The wires were swapped from #3 and 5 cylinders to fix the problem. My "service engine soon" light came back on after the fix with code P0420 (Catalyst efficiency deteriorated - LH bank). Any ideas how to further isolate the problem? I can't afford to replace all of the cats and O2 sensors *****-nilly. Many thanks in advance for your help.

2004 Discovery II
107k miles
O2 sensors replaced around 70k

 

I'd drive for a day or two (or three laps around I-285) and reset and try again. Here is a page on that code, it will come back after being cleared if it happens on two drive cycles. The exact text of a scanner may not match the Bosch designer's. Whole manual is available for free download if you want that sort of technical info.

My read is that it would be the rear sensor on bank 1.

 

Unfortunately, I already reset the computer and disconnected the battery for 2 hours but the code came back after about 20 miles. The code description I listed was from the RAVE, not what was captured by the scanner.

 

Well, the RAVE (p 331 of 1529) does not tell you where, but the LR Bosch manual does point to rear sensor on that side.

 

I would still try to run it threw a few more drive cycles. If its not running poorly anymore that is it may clear up on its own.

 

And for anyone reading this thread, quit disconnecting the battery as a fix for problems, it rarely fixes anything and cause your ECU to loose it's additvie memory.

 

I was wondering about that, because a P0420 is supposed to take two drive cycles. I would wonder if the battery disconnect resets all of the memory, since his came back at once. Perhaps reset with a scanner will yield better results.

 

I guess I need to buy a scanner since the auto parts stores won't clear my codes. Does anyone know if it takes a standard 16-pin OBD-II connector? Anybody seen a cheap version online that they know will work for the Discovery II?

 

Is is an OBDII. You might want to look at an Ultra Gauge, $70. It read and reset codes, plus displays live data like coolant temp, and you can set alarm points.

 

Ultra gauge is a good choice you can plug in to your obd II port and hide the wires up behind your dash. Buy the suction cup mount and fix it to your windshield then you can pretty much ignore your gauge cluster and pay attention to the UG as buzz stated you can set alarms to go off in almost any instance. There are 7 different pages you can set up however you wish all the way from mpg to live o2 sensor readings, you can clear codes and read them as if you were sitting at autozone. All in all this device has saved many rovers.


The clean air act is what has forced your local auto parts store from being able to clear your codes incase you were wondering.