2003 Murano odd O2 Sensor Readings, Old Scanner to blame?

[walczyk]

To start off, I have lean codes on both banks and my 2003 Murano has 6 wire O2 sensors, and the 2003 FSM does not have the right upstream O2 sensors (they expect 4 wire) and even dealer websites do get this right, so that bothers me. Also, I think this old Bosch scanner can't really properly display the currents in these modern 6 wire o2 sensors, and instead tries to display voltages. In either case, I think the STFT pattern for Bank 2 shows that the cat is clogged. After an hour of driving, the throttle response goes down the tubes and it slugs along from a stop. I've had the bank 2 O2 sensor melt on the inside, I think it is a clogged cat. But the strangest thing is Bank 1, its O2 sensor has half the voltage of Bank 2. But what's stranger is that these fancier 6-wire O2 sensors care about current I believe. The FSM doesn't really correlate to what my scanner says.
 
Here are two snapshots.




The last image is when I let off the gas after accelerating for awhile (guessing this is the fuel shut off behavior)


Does anyone know about this 2003 Muranos having 6 wire O2 sensors? (02/2003 is on the label of my car) Any recommendations for a better scanner? I wish I had a consult ii. What should I do first? This is an enhanced OBD1 and OBD2 scanner, so it''s really geared toward older cars and I can't trust it.

[VStar650CL]

I've never heard of 6-wires on a gen1 Murano, the only 6-wires Nissan generally uses are on Cali cars and the '03 Muranos didn't have a Cali version. So I dunno what's up with that.

Unlike later models, the '03 VQ's still had HO2S on the front and rear, not A/F in front and HO2S in back. Once they're warmed up none of those voltages should be steady, all four should swing up and down between about 0.3~0.8V. The fronts should swing at about 0.5 Hz, the rears should be quite a bit slower if the cats are doing anything. You can't check them at idle, that's meaningless. Either take it on the highway or keep it above 3000 RPM for at least a couple minutes to get a valid response.

Engines are air pumps. If you think a cat is clogged, the best test is actually an old school vacuum gauge. When an engine can't breathe it will read normal vacuum at idle (say, 18~20" Hg), but the vacuum will drop way off when you raise the RPM's and you'll get a very distinctive low-pitched howling noise. On a healthy exhaust the vacuum will drop initially when you raise the RPM's, but it will recover quickly and no noises. If you don't get the howl and vacuum loss, then your problem isn't a clog.

[walczyk]

I've never heard of 6-wires on a gen1 Murano, the only 6-wires Nissan generally uses are on Cali cars and the '03 Muranos didn't have a Cali version. So I dunno what's up with that.

Unlike later models, the '03 VQ's still had HO2S on the front and rear, not A/F in front and HO2S in back. Once they're warmed up none of those voltages should be steady, all four should swing up and down between about 0.3~0.8V. The fronts should swing at about 0.5 Hz, the rears should be quite a bit slower if the cats are doing anything. You can't check them at idle, that's meaningless. Either take it on the highway or keep it above 3000 RPM for at least a couple minutes to get a valid response.

Engines are air pumps. If you think a cat is clogged, the best test is actually an old school vacuum gauge. When an engine can't breathe it will read normal vacuum at idle (say, 18~20" Hg), but the vacuum will drop way off when you raise the RPM's and you'll get a very distinctive low-pitched howling noise. On a healthy exhaust the vacuum will drop initially when you raise the RPM's, but it will recover quickly and no noises. If you don't get the howl and vacuum loss, then your problem isn't a clog.

Yeah it's quite strange, but they are definitely 6 wire! The pictures are from when I was driving. Could a dealer look up work done by VIN? I got a back pressure vacuum gauge I'm going to use today and I own an old school vacuum gauge in generral. When you say read normal vacuum, do you mean from the scanner? I am going to use a vacuum gauge at the o2 port.

[VStar650CL]

No, from the gauge. I don't recall any MAP/BARO on the gen1 Muranos, so you can't get it from a scanner, it has to come from an external gauge. Not sure what you mean by the O2 port, you need to be checking unported intake manifold vacuum and not the exhaust system.

[VStar650CL]

PS - The easiest place to pick up unported vacuum on those engines is between the plenum and the vacuum reservoir. You can actually use either hose on the reservoir, so if your gauge has a nipple then take the reading off the inlet hose, if it has a hose then take it off the outlet nipple.