diagnostic help needed: LONG

.4v no matter what. so that means something is dead, right? or do i read your post as i have a bad ECU? 

how do i use a multimeter to test the sensor itself? cause im hoping jim got a bad one out of the box.....

Dusterbd13 said:

.4v no matter what. so that means something is dead, right? or do i read your post as i have a bad ECU? 

how do i use a multimeter to test the sensor itself? cause im hoping jim got a bad one out of the box.....

Are there two such sensors on the car?  If so, switch their positions and see if the DTC follows the sensor.

The second picture in the first post was with the two switched. I think it follows the sensor, but wantindependent confirmation, as lately every conclusion i make is wrong...

Sensor ground?

Dusterbd13 said:

.4v no matter what. so that means something is dead, right? or do i read your post as i have a bad ECU? 

how do i use a multimeter to test the sensor itself? cause im hoping jim got a bad one out of the box.....

It is more likely to be the sensor. And most likely to be the wrong choice of replacement, since both are doing the same thing. 

Or that they were both incorrectly installed. 

Just want to make sure: b1s1 shows .1-.3v while running. B2s1 stays at .4v

Or did you mean something different with "both sensore do the same thing "?

Dusterbd13 said:

Just want to make sure: b1s1 shows .1-.3v while running. B2s1 stays at .4v

Or did you mean something different with "both sensore do the same thing "?

According to the DTC's you are pulling, there are errors with both sensors.  

Ok.

Could it be that b1s1 is trying to overcompensate for the non functional b2s1? Or am i overthinking it?

Check the grounds to the O2's.  Can you you run an independent ground without too much trouble?   Also, check the harness to the ECU.   As stated in my post, the harness had some bad wires, ie: chafing and corrosion.  Hope this helps ya.

Dusterbd13 said:

Ok.

Could it be that b1s1 is trying to overcompensate for the non functional b2s1? Or am i overthinking it?

No, they are independent of each other in terms of the error you are getting.  

Yes, if one sensor is totally out, the other one will be used to direct for that bank, but it's in a different section, and not what seems to be the problem.

Maybe this under hood diagram can help tracking and show you locations of wiring.  

So this morning I swapped sensors bank to bank and watched live data. BOTH sensors stayed at .4v

Which tells me that the b2s1 is dead, AND the wiring between that sensor and ecm us bad. Right?

I also have a moke machine coming.  Time to look for vacuum leaks again.

Dusterbd13 said:

So this morning I swapped sensors bank to bank and watched live data. BOTH sensors stayed at .4v

Which tells me that the b2s1 is dead, AND the wiring between that sensor and ecm us bad. Right?

Inspect the heck out of the wiring.  And get the right sensors for the car.

BTW, for the heater and the signal, the ECU is providing the ground- so make sure it's properly grounded.  But that's all the ECU does is provide ground, to allow power to flow through the system.

Will do. 

According to the previous owner (from here) they are bosch sensors with now ~500mi on them. Purchased by the listing for the car at orielleys. So, we can ASSUME they are the proper sensors. However, is there a way to confirm?

Also, ill need to find a pinout diagram for the ecu. Theres about 200 wires going to it.....

Any help on that? Im assuming standard continuity test will be sufficient, correct? I tried without a pinout, and failed miserably. 

In reply to Dusterbd13 :

No, I would not assume they are correct.  I would assume they are not correct, so that you can use process of elimination to figure out what is wrong.  I just tried to buy a fuel pump for my Miata of similar vintage, and NOBODY has the right part, other than the dealer.  It was a "direct fit" replacement, that required wire splicing.  Every parts supplier had the same kind of thing, including Flyin Miata.  That's not a bash on the parts suppliers other than even the good ones don't have the correct, plug and play, part.

No idea where to find a pinout for your specific car, but there should be some very good grounds going to it.

BTW, look for wire faults under the hood- that's the bad environment- not in the passenger compartment.  

The two volume Bentley for the E39 devotes one book to electrical. I sold mine with my E39, so I can't tell you if it has an ECU pinout, but that's where I'd look first.

There's a good chance that the sensors from the local auto parts store are not correct. There are so many variants, and these cars are so sensitive, that any deviation is likely to cause issues. FCP Euro shows Bosch 13477 as the correct sensor. Not sure if you'll be able to find out what's in the car now, but if you do and it's not 13477, I'd be looking to get the right parts in there.

It does have 13477 in it.

Have a replacement (under warrenty!) On the way. 

Now its a matter of pinouts and continuity test. 

Looking at the wiring, it APPEARS that all the 02 wires go to one specific plug. So, that will be step 1. 

Well, step one will be finding paperclips or safety pins that fit the pins so i can get a reading with my multimeter.....

to make sure you've got the correct sensor:

1.  goto realoem.com

2.  enter the last 7 digits of your VIN

3.  dig into the exploded diagrams and find the sensor in question

4.  cross-reference the OE part number to what is sold by FCP Euro, ECS Tuning, or Pelican Parts.

5.  is that what you've got?

The oxygen sensor are definately correct. Rear gaulty sensor replaced. However, since both sensors lock at .4v, i believe that the b2s1 wiring is bad as well. With that thought in mind, did some multimeter testing today. 

all the following results are b2s1 chassis side wiring

all pins have voltage at the oxegen sensor end, varying from 3.6 volts to 11.36 (battery voltage)
no pins have a ground
all pins have no measurable resistance between the DME connector and corresponding oxegyn sensor pin. 

the b1s1 has 2 pins with voltage, and one ground. the return to DME ohms at 0. 

bad dme? or is there harness damage im missing somewhere that i havent found yet?

Michael I applaud for your focus on this...to most this makes everyone's eyes cross and they fall off the 'puter chair. But for some lame brain reason I'm diggin' the E36M3 outta this cuz on the local 'car doctor' radio show today almost every other call was about some 'electrical' gremlin playin' hell with progress.....carry on BRO....oh and big ups to AlphaD.....and you too AngryC 

OK, I finally found the wiring diagram for this. I'm not great with electrical diagrams, but it appears the heater circuit is red/white positive and brown ground (brown is always ground on these cars); the sensor circuit is yellow supply and black signal return.

You have continuity on all wires from the DME plug to the sensor plug, correct? Before condemning the DME I'd go through the harness with a fine-tooth comb and try to determine that all the wires are good, since there are only four and the circuits are relatively simple.

In reply to Dusterbd13 :

The two heater lines- one gets a 12V from probably the key power line somewhere.  The other is grounded through the ECU- just like all of the injectors.

The signal wire should find it's way to the ECU, too.  I'd have to look how the signal ground is grounded.

The b2s1 should have a ground. I'm worried about that harness.

Wait, were both sides done with key on? Same position?

It is curious how the dme seems to be grounding the heater on bank one but not bank two.