Quote:
Originally Posted by MB-Dude
Brett – The vacuum line goes from the Brake Booster, through a dividing wall, curves around the #12 coil, and then loops to the upper-rear of Bank 2 where it goes into a three-line connector (?), or something. This connector (if that’s what it is) feeds directly into what looks like the bottom of the intake manifold. But in fairness, I am typing this from memory and only after a very brief glance. If you want, let me know and I’ll get a picture tomorrow.
Just to recap, looks like Brett and I have the same issue – Bank 2 Pre-Cat O2 Sensor reports zero output. This would normally imply a very lean condition. However in my case, the engine runs very smooth and strong. This suggests the ECU is receiving O2 data, computing air-fuel mixture correctly, but not reporting proper O2 status. Thus, the ECU’s are not reporting a ‘Ready’ state.
Thanks again to all. I’m starting to get into areas I have no expertise; i.e.: ECU’s, etc. Any and all input would be really, REALLY appreciated. Thanks to all.
Cheers,
Jeff
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Sorry, if I'm insulting your knowledge on this topic, but just to be sure. You seem to be saying that the bank 2 intake is on the left side of the V12 engine. Actually, it's the opposite. The intakes cross over the engine and feed the opposite side. So the left side intake and throttle body are the bank 1 intake and throttle, and vice versa. I just want to be certain we are always talking about the same thing.
Before I even think about ECU replacement, I'll trace the O2 sensor wiring and make sure there are no continuity issues. If you read all the diagnostic procedures in alldata (same as the MB service CD's) wiring is listed as a possible cause in pretty much every single one (not surprisingly). What I don't know is the wiring relationship between the OBDII connector, where we are reading the O2 sensor signals, and the O2 sensor itself. Does the signal go to the ECU and then get relayed from the ECU to the OBDII connector? If so, doesn't that mean it is possible that the wiring between the ECU and the O2 sensor is perfectly fine (ECU is getting a good signal.), and the problem then is simply bad wiring between the ECU and the OBDII connector? And the ultimate result is that we are getting a false bad O2 sensor reading, and we are chasing a red herring... I've got to dig up some wiring diagrams. Alldata may have them. We need to be able to read the O2 sensor signal right where it gets to the ECU.
The reason that I like this possibility is that I have no fault codes related to the bank 2 O2 sensors despite the flat pre-cat signal. I would think that fault codes would abound under those conditions.
And, finally, I checked my brake booster. The booster on my car is fed vacuum directly from the intake manifold. You are right. The line T's and goes to each side of the intake.
Brett