Thanks for the rehash. Seems odd. So CPS and MAF wires might get near each other in the loom. Long shot, but wiring damage during CPS work might have affected the MAF? How does it do if the MAF is unplugged? It should default to the factory map (based on throttle position and rpm), and throw a different code. Maybe trace down the wires for CPS and MAF circuits looking for shorts. The O2 trends look good, by the way. Maybe check the downstream O2 trends to compare, they might be involved in the Monitor. The downstream O2 trends should follow the upstream trends, but less extreme.

 

Have you tried a good cleaning of the MAF?

 

This is actually MAF #3. I cleaned the original, bought a cheap chinese replacement off of amazon, then in a fit of rage (and questioning my DIY skills) broke down and took the truck to a shop that specializes in brit cars. They replaced it with a new OEM Bosch MAF.

Interestingly, a guy on reddit pointed out something that had escaped my notice... The MAF readings are high. If there were a vacuum leak downstream, the readings would be lower than I'm seeing.

I did a quick and dirty stall test -- covering the MAF housing with my hand -- and it stalled immediately. So, only metered air is going in, and it's too much metered air at idle.

I'm currently going down a rabbit hole graphing and analyzing some nanocom data. I'll put that up once I work out the kinks in my code.

 

OK, so I graphed the up and downstream O2 data and I'm not sure if this is correct (i.e. expected) janky sinusoidal?


Some other things I looked at were the throttle data, thinking that maybe it was more open than expected and pulling in more air at idle, but it was steady at just a bit over 3.1% which I think is within normal parameters.

And I'm really not sure what to make of this fuel trim data. Assuming I didn't make any mistakes, it looks more like modern art than useful information to me:

 

Whoa. Staring at it for a minute, it hit me, downstream is flat at about 0.45 volts... So, dead downstream O2 sensors?

But I'm still confused about why I'd have such an oddly high metered air reading.

 

IIRC downstream sensors don’t cycle.

 

Also, downstream sensors don’t modify your fuel. They just monitor whether your Cat is doing anything.

 

So fuel is being modified correctly, as shown by the upstream O2 sensor trends. The downstream sensors could be part of setting the O2 Monitor, even though they are not involved with fuel modification. Getting the Monitor to set during the drive cycle is the problem that needs to be solved.

For D1s, if any of the four O2 sensors are at a fixed, steady value, that will throw a code, because the software is smart enough to figure out when the circuits have been modified (e.g. a resistor in place of the sensor) to try to fool the ECM. Perhaps the downstream sensors should move a little, just not as much as the upstream. Maybe monitor the downstream O2s during a cold start and warm up. They should start at one end, then ramp towards the middle. Both banks should act very similar. Depends somewhat on the condition of the cats and sensors.

 

Been a while since I posted anything here... Sadly, no luck. I replaced the O2 sensors and took it to a shop and gave them the history and the data I've collected.

They ended up not charging me after spending quite a bit of time digging into it. They said that mechanically, everything is fine. Their best guess is that there's a wiring issue somewhere between the ECU and the throttle body.

I'm not sure what to do at this point. California smog was due almost a year ago. Smog referees won't touch it. I called a land rover specialist in Santa Barbara, and they said that the D2 isn't really something they'd work on.

It runs great, but I'm SOL unless I can get it smogged. The only thing I can think of doing at this point is trying to sell it to someone in a state that doesn't do emissions testing OR will do emissions via a sniff test rather than OBD.

Anyone want a D2 for a farm truck?

 

Have you inspected the throttle actuator? Not the linkage but the shaft attached to the butterfly? One of my 04s jumps up to a high idle on cold start and I assumed this was throttle body heater related because I first noticed it over the winter. Now that we're into the warmer weather the truck still does it and I've noticed that the butterfly is sticking. I can force the linkage closed with my hand and the idle returns to normal, and there's the specified gap in the linkage, but otheerwise the idle remains high until the truck builds enough heat to relax whatever is sticking in the throttle shaft. I'm not sure how that could affect the rest of your situation WRT to code and monitor readiness but I thought I'd pass it on. I can send you a throttle body if you want to try swapping it to see if that helps at all. By the way, did this situation start with the changing of the VC gaskets?