Hi guys, I just changed both upstream and downstream O2 sensors on my 2004 discovery, downstream ones are aftermarket and upstream ones are NTK. Downstream ones were done 2 days before upstream ones, a few miles after doing my upstream ones I get P0130 and P0150 codes, connectors are clean. On my Ultra-Gauge I get normal voltages for all of them but after warming up they get all over the place, sometimes at zero volt and come back to a normal voltage. My idle is pretty rough since changing them. Vehicle is at 180K miles and was running very well before changing the sensors (even if I had a P0154 code), also I cleared all the codes and even tried disconnecting the battery to do a reset but the codes are still coming back, any ideas?

 

Literally…literally… exact same struggle here. New 02 sensors, same codes. Just went ahead and replaced the sparkies today and coincidentally (?) spark plug #4 is totally worn down, and the rest are no better. I think this might be the issue. Odd timing though. Worth a check on your Disco if they haven’t been replaced in a while.

 

Usually it's recommended to reset the adaptive settings whenever you change a sensor like the MAF or O2 Sensors

 

Ok you won't believe this... I was looking at my spark plugs and my #4 wire was completely broken from the sparkplug connector hahaha weird coincidence, I will be replacing all wires do you think it could solve the problem?

 

Didn't know that thanks! Also I get lean codes, I guess it's from bad O2 sensors readings?

 

OMG that's amazing, haha. How strange!

I've been doing a slough of research on this and most past posts suggested it could be basically four things: spark plugs, plug wires, coil packs, or fuel injector. I didn't know when the last time the PO replaced the spark plugs were, so knew even if they didn't solve the issue (TBD on that, time will tell) they needed to be replaced anyway. And the next cheapest, easiest procedure is wires and coil packs, and then if all else fails, the last and most expensive is a fuel injector. So definitely worth a shot to replace the plugs first.

 

Tomorrow I will do spark plugs, wire and coil packs I hope it works! Thanks for your help!

 

I got P0304, when ignition wire cylinder 4 got cut (banging against SAI pipe and heat made the insulation brittle). Installed new ignition wires STK 721. Make sure the wires are always attached to the valve cover.