I am at the last and final straw with this Rover. I am calling all those with the best problem solving minds out there. Here's what I know and have done. 2000 Land Rover Discovery 2. Since January I have had a check engine light on. March I needed to get emissions done. I finally looked into it to see what needed to be done. I had every sensor showing me a code saying there was either no o2 sensor activity or their was a heater circuit short. After testing each wire to the ECM to find that there were no shorts, I tested the ohms on all the heater sensors and all of them were at 1.7 ohms. Later after I bought brand new OEM o2 sensors from Atlantic British I learned that the ohms were all at 1.7 when cold. But I replaced all 4 of sensors anyways. Cleared the CEL and drove it around a bit. After 3 cycles, all the codes went away except B2S2 sensor showing P0160 (no activity) and P0161 (heater circuit malfunction). I swapped the rear sensors, cleared the CEL, those same codes came back. I tested each and every wire of that sensor right back to the ECM as well as the heater circuit to the battery. Everything has connection. I even checked the pins that directly plug into the ECM. At this point I decided it had to be the cats. So installed a brand new magnaflow Y pipe with both cats already welded. I checked the welds too. After installing those I cleared the codes again. I started the car and everything ran real well. After 15 minutes of ideling, I got the pending P0160 code. It doesn't make sense because the scanner show's voltage and the correct reading from that sensor so I know there is activity! On my way to work this morning the CEL popped on again. I am through with this vehicle. If you have read this far please help if you have any information at all. I need a miracle at this point. Thanks, David.

 

What if your sensors are telling the truth and you have another issue, like a vacuum leak, spark, fuel injectors?

 

Thank you for your reply. Help me understand why a vacuum leak would only effect one sensor? Why wouldn't a vacuum leak cause multiple o2 sensor codes? Also how would spark and fuel injectors cause that code if the voltage is reading the correct voltage at .450? I'm just confused.

 

Ok, I read a little more and I think you’re right. I’m assuming that the only code that keeps recurring is P0160?

 

Yes, that is correct. Before the I installed the new cats I had just the P0161 code and the P0160. Now after I installed the cats I cleared the codes and now it is only the P0160. But I'm still getting a voltage of around .450 so there is activity. That is what is so strange.

 

Have you charted the activity with an analog graph? disconnected the sensor to see if it goes to zero? The 2nd set of sensors is only for verifying cat function. One other thing to consider, a 2nd set of ECU-BCU-IC. Better if you have a known good set, swap it in to verify it is not a bad ECU. I did have one ECU where the oxygen sensor drivers went bad (it was the fronts). Different ECU fixed it.

 

I agree with everyone above. It's time to think outside the box and at things that sensor is responsible for. Oxygen.

You've eliminated that the sensor is bad in every way you possibly could. You've eliminated a very expensive part of the exhaust.

If it were here I'd break out the smoke machine and remove the O2 sensor causing the fault and put my smoker in and clog most of the exhaust tip (you don't want to create an airtight deal, just force smoke out of any possible holes. I use scented baby oil, sometimes you can smell it and not see it.

Then grab a drink, hang out with your partner in the shop⁰, lay on a creeper and give it time. Look at places in that exhaust that you have not addressed - manifold, the head itself for little cracks.
Maybe the gaskets on the new cat are not flat etc.

If you're super sure about the exhaust, move onto vacuum. Same process. Put on some piano guys music, grab a drink to lure your partner out. And just smoke that bank. These cars don't have a good one-hole-to-rule-all-other-holes so take things apart, cap off one end, smoke it.

Same principle, you don't want to cause leaks so nothing needs to be air tight.

I take off the maf and use a glove with a hole or two and a hair tie on throttle body.

The age and unknown repair history of our trucks make it hard for anyone to pinpoint the issue.

You might find it's because a previous repair was grey rtv where grey rtv has no business being haha.

 

Thank you for reaching out. Help me understand why an exhaust leak or a vacuum leak would give a P0160 code?

 

I know it's pretty misleading, but the codes don't specifically tell you what's wrong, just the general area to look in. They are industry standardized, not vehicle specific, and the words used for the code definition can not be taken literally. So when you have a P0160 O2s sensor circuit no activity, that can mean a myriad of things, up to and including things like vacuum leaks. The only thing you can be sure of, is that your vehicle, with it's highly simplistic way of seeing the world, thinks there is an issue with it's O2s circuit.

For instance, I've seen that codes like that pop up from a tiny bit of oil dripping on the O2s connector from a valve cover leak. Fixed the leak, cleaned the connector, problem fixed. I've seen codes like that for vacuum leaks as well. Not terribly difficult to smoke test a system looking for vacuum leaks, check Youtube for helpful instructions on making your own smoke tester for cheap, and how to use them.

I would say, that if you do not want to become an mechanical wiz, you might not wanna have a D2. They aren't the worst I've ever worked on, relatively easy compared to most, but they are quirky, and much of their electrical systems are unique in the automotive world, making them require intimate knowledge to fix. I know the LR repair shops here in Colorado charge $275 an hour, plus a 1.7 per hour multiplier....yea, these things can be highly frustrating to diagnose sometimes.

Lastly, for what it's worth, I see you've traced and tested every wire and connector in the system, and are using known good/new O2s, suggesting that good information is being fed to the ECM, I would begin to wonder if that info is not being used or interpreted properly by the ECM (which could be caused by a vacuum leak, etc). But again, don't take the definition of the CEL code literally, see the problem from a bigger perspective, and diag from there. Basically, all you really know right now, is that something in the way that bank of cylinders is burning fuel is wrong. And that after some time running like that, it's causing the other bank of cylinders to also become imbalanced, throwing the other code as the system is trying balance things....

 

Thanks for explaining all of that. I sometimes take those code readings literally. I planned on dropping this truck off at a trusted auto service but I might just try to look for vacuum leaks. Hopefully I'll find some answers.