Car threw a code 64 (right bank lean) on my way to work today. Here is the weird thing. The right o2 sensor is scanning like it should it's the left o2 that is reading almost a constant .003mv. Right rbl is a constant 160. I can't for the life of me figure this car out. What could be the problem?

 

Anyone? Maybe I'm reading this wrong but here is a vid showing the left o2 at .003mv with a dtc 64.

http://s20.photobucket.com/albums/b2...t=SANY0022.mp4

 

The fact that your INT's (lin, rin) are locked at 128 would indicate its in open loop. Had the engine been started less than 3 minutes before you took the video? If it is in open loop, is the AIR pump still running? That's what normally causes an 003mV reading in open loop. In any case, since its in open loop, its not changing the BLM's (lbl, rbl) - (learning disabled in open loop) - only does that in closed loop. So the "lbl" is not going to respond to the 003mV reading.

The difference in BLM's may be accounted for by the fact that the left side is running with the AIR pump on, dropping the O2 mV's and the right side may have the AIR flowing, or may not, and the 160 BLM (possibly a response to a "false lean" condition) is pouring excessive fuel in to the right side.

You need to see what its doing in closed loop.

 

I no longer have the air system. The car had been running for about 15 min at least. It will only run a minute or so in closed loop before the ses light kicks on. Right before the ses light kicks on it starts running like crap. Rough idle, no power. Once the light kicks on it idles and runs better. The o2 sensor on the left bank is a brand new delphi. The right is the original o2 sensor.

Doesn't the o2 mv need to be below 2xxmv for a while before the lean code is given? I have watched the right o2 sensor readings before the ses light kicks on and it was in the 700ish range.

What should I be looking for while in closed loop?

 

I don't see any evidence in your brief video its going into closed loop. A faulty O2 sensor will prevent that. Neither sensor is swinging back and forth over the full range (right side appears to be stuck in the mid 700's), and the INT's are both (seemingly) stuck at 128. It's not in closed loop from what I can see.

The early PCM's set the code for the sensor being under 200mV for 50 seconds. The later ones (OBD-II) set the code when the weighted average of the BLM's approaches 25% (160). Not sure what the logic is on the 95... I don't have a 95 manual.

Try switching the sensors side-to-side.

 

The ses light had already came on when I took the vid. I will try and record another vid while it's in closed loop.

I'll try that however I have had problems with the o2s on this car since I got it. I've replaced the left one twice now and it still won't sweep through the entire range. Mostly stuck in the 350ish-550ish range. Even when I switched sides .

 

A disconnected O2 will read 450. That together with the fact that you throw a code as soon as it tries to go to closed loop indicate you have a break in the signal wire.

 

Switched o2s, same result. The left o2 started in the 8xx range then rapidly dropped to .003mv and stayed there. The right o2 started at 450ish then increased to 700ish then started moving from 200-700. Then the ses light kicked on and the right bl shot straight to 160. I checked for leaks at the collector and all the flange bolts are tight on the headers. I checked the o2 wiring on both sides and it looks fine.

Where do I go from here?

BTW when I took the right 02 out it was covered in black soot. The left one still looked brand new.

 

Bad O2 wiring.

Define 'checked'

 

I visually checked the wiring looking for bare wire or cracks. I can't see the section going behind the intake for the left side though. I can check continuity from the pcm harness to the o2 plug ends and see what that turns up.

 

Ok I checked for continuity through the harness from the pcm to the o2 sensor and there is continuity. Then I did something that really makes me want to bang my head against the wall. I left the drivers side o2 unhooked. Started the engine. The right o2mv stayed at 449 while the left (the one that is unplugged) began at 9xxmv then slowly dropped to .003mv. It's like the computer don't know it's left from it's right. WTF?

 

I just unplugged the right o2 sensor while watching the left o2 reading and sure enough it went from .003 to 450mv. How can this happen? Faulty pcm? Should I try and switch the wiring harness around?

 

It would be awful hard to connect the harness to the wrong sensor... right side wire is bundled with the starter and knock sensor wires, left side wire is bundled with the oil level and pressure sensors.

Check the pinout on the PCM. Left sensor (purple/white) to pin C20. Right sensor (purple) to pin C8.

 

Near zero plugged in and the correct 450 when unplugged indicates a short. But unplugging the right and the left reading changes????? Only ever saw that type of response when they were crossed. So see if the harness has enough space to switch them. Then test the O2 sensor in question for a short.

 

I checked the pins on the pcm connector they are correct. I switched the pins around. Seemed a lot easier than switching the wiring. Then I tried to start it. The right o2 starts out at 9xxmv (like it always does) then starts scaning but the numbers slowly drop to .003. I thought the voltage is supposed to start low then rise as the o2 heats up? As the right o2 voltage dropped the engine began running really rough. The lbl went to 160 and the rbl dropped to 108, which again is opposite of what it should be doing .

I'm stopping today and getting a new o2 for the left cause I'm sure it's dead. It starts at 450mv then rose to 7xx then didn't move much.

What would happen if the tan and purple wires were switched?

How would I test the o2 sensor?