Interesting - so I installed a new NTK sensor, 25623, which is an upstream sensor. The photo on RockAuto's site (and others) show this with a gray connector instead of orange. The one I received had a gray connector too. I installed it and immediately got a CE light and P0134 again. The Ultragauge showed it staying static at 0.445. Dead sensor? Wrong sensor? I'll reinstall the old Bosch while I figure this out.

 

I have long suspected that the only difference between D1 and D2 sensors are the connectors but I've never owned a D1 so I can't say for sure. In the limited research I've been able to do by comparing images online it looks like the D1 uses pins on the upstream sensors (male) and the downstream sensors are opposite (female). The D2 definitely has the pins on the body side harness for the upstream sensors and the downstream sensor has the male pins on it so my guess is that's the big difference since the 3.9/4.0 engines are similar. I've never seen a D2 upstream with a gray connector either so I'd guess you got an incorrect sensor, but dead is certainly an option too. How long did you let it warm up? I've already installed the two BOSCH universal sensors I bought the other day and it took >90 seconds for them to warm up based on the graph. That won't change the fact that you get the CEL however so something is likely wrong.

By the way, this is at least the fourth time I've done this dance and as often as you guys get dead/offbrand/sketchy sensors, I've never had an issue with the sensors operating correctly once installed but I get screwed by the actual install every time. There's no way the senors were coming out on the truck, as usual I had to drop the pipe and even then they wouldn't budge with an impact gun until I heated the pipe with a torch. And look what I was left with.



This after going back and forth slowly and trying to back them out with care. It was a bear to save the threads but I was able to avoid welding new bungs on this time too. I'll once again recommend the $30 BOSCH universal sensors if you end up repurchasing.

 

Bosch is the only way to go. Replaced both my upstream sensors when I rebuilt my engine with the more affordable options. Believe they were NGK with the grey plugs. Both died within 3k miles and about 3-5 month of use. Both have been replaced with Bosch with 1 year warranty. Already got more life out of the Bank2 Bosch than I did either NGK. I've learned the electronics on these old Rovers are just so sensitive. They just don't seem to like anything other than OEM quality parts.

 

Welp! If you guys feel like you might be the worst mechanic on the forum, just remember this post: The issue I was having with the new NTK was that it wasn't plugged in. So that's nice Plugged it in, installed another new one on the other side, reset the CEL and all is well.

 

Interesting. I've had terrible experiences with Bosch sensors (which tend to be the most affordable ones), and have had to replace two on this Disco prematurely. This is my first round with NTK, but in terms of quality, they're pretty much as good as it gets. I don't know where you got the idea that they're somehow a lesser brand. The Bosch sensors were about $35 and these NTKs were about $70. I guess it's all anecdotal ¯\_(ツ)_/¯

 

Hahaha. I can't say I haven't been guilty of similar gaffes. The best part is the all is well part...

 

I did look at my receipt and the failed ones were Walkers. The Bosch was $60.00. I see Rock auto has them on closeout for $32 right now but I didn't want to wait so I just went to my local brick and mortar store.

 

O'Reilly cares the NTK they are close to $100 each - they are the best quality - you might find them closer to $75 at places - Denso would be another quality brand over Bosch - IMO since they are a PITA to change this is where I would go with best quality - I think autozone has a 25% off on them if your purchase is over $100 - good deal