JDVIKING

2005 E500 144K
So like the title says I need a little help with a DTC that is a stubborn SOB! Please chime in with anything you deem relevant or helpful. Quick recap can be found in my other thread https://mbworld.org/forums/e-class-w...0everyone%20JD
(thanks BlackML550 for hanging in with me in said thread) where I'm at now ONE code P0151 that needs to be gone ASAP I have 3 days left to smog car. So basically the code means O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1). Possible causes..... well causes if going by the book are O2 sensor, pigtail connector at O2, leak in exhaust bank 2 (near to O2) wiring issue, a legitimate "Lean" condition is present and on and on ..... Here is what I have done replaced O2 sensor 3 times as I was not in love with idea of an off brand sensor i had in the box new so did install a new Bosch. Swapped complete engine wire harness in primo condition. So on scanner both upstream o2's are similar but bank 2 does drop lower under 100 millivolts for brief moments though and both upstreams climb as high as 650-700 but again briefly. I checked exhaust pretty well for leaks soapy water and all, good compression on all 8 lighters,all injectors and plugs are good. There is no miss in motor anymore all issues that came with the 7 code (actually was 10 codes) nightmare are gone i.e the secondary air pump functions perfectly all info documented in other thread. One final late afternoon discovery today I was so focused on the upstreams that I overlooked the reading on Bank 2 downstream of 32 millivolts steady? Now thats hella nuts!

JDVIKING

Just an update po151 code then I got 154 and now 155 is stuck on I'm assuming that new O2 sensor now failed although on the scanner the readings are good except for 32 millivolts on the bank two ....she does not throw a code for num two, just throws it for the number one sensor on Bank two (upstream).... I was looking for some replies nobody anything?

nd-photo.nl

What are the fuel trims saying? Are they close to 0 or more towards -10% / +10%?

Did you also check for vacuum leaks or leaks in/around the intake

JDVIKING

First TY Andy for taking the time to reply, beautiful CLS by the way! So I've had the intake on and off at least half a dozen times, and most recent removal did a smoke test with my own designed smoker lol...(actually the smoker's pretty bad azz)
*** far as the trims they read "okish" at minimum they are left/right consistent, I have adjusted both on lean and rich 10-20% ....when I went rich the engine didn't seem to happy!!
Odd note at present moment car has 5 of 9 monitors closed or "ready" no code (need just 3 more to close per smog law here) the O2 sensors show closed and ready Next I'm confident the secondary pump will close still with no code, but p0151 will pop up when 7th monitor (Catalyst I think) shows complete 0r ready .

JD​​​​​​​

JDVIKING

well it appears I'm heading down the rabbit hole with a sudden much more serious issue!! Put about 4 gallons of "Premium" gas (91 Octane) premium was facetious.... anyway after the fuel I pull out rather hard but not "on it" hard and immediately I feel the car stubble hard and starting to misfire I limp it home (less than a mile) hook up to scanner and find these....

CaliBenzDriver

You have 3 misfiring codes: 1 hard set + 2 transients.

I am curious how did you adjust your fuel trims ??


-- How much is your fuel pressure under load ??

-- How much are your LTFT's at idle ?
​​​​​​​(both near zero or -10%)

JDVIKING

Thanks for responding CaliBenz
Let me first correct my wording as I should have said was I adjusted on the adaptive fuel "mixture" going both ways (lean and rich) this is really only for testing purposes, depending on what scan tool your running
(star aside) you can record the LTFT or STFT as you adjust adjust the the AFM.
FP was strong at Idle (53-54) and increased under quick revs to 56-57 on road under a load was a tic less if i remember right....but not enough to even feel in car...