cnterline

03 SL 500 Kleemann s/c w headers,front cats gone,rear cats have secondary 02,s after them ,keep getting p0131 and p0151 on scanner,no CEL but it wont pass inspection like this,Cory at Kleemann has been real good about trying to help me but Im in NY and cant bring the car there ,new primary 02,s,no vacuum leaks,no exhaust leaks,these codes in my scanner say low voltage bank 1 sensor 1 and low voltage bank 2 sensor 1,mercedes codes say short circuit in the signal line on the 02,s I dont know if this is common on a car with these mods and there really is no fix ,or has anyone out there had a similar problem after similar mods,I know this is the wrong forum but there are alot of hi perf guys on this forum,any help or suggestions would be appreciated,I have auto tap and watch the o2 functions but I dont see anything glaring.sometimes it takes awhilefor the codes to come up but they always do,been chasing this problem off and on for a year thanks Kevin

ctravis595

i've been dealing with a similar issue, was wondering if you found a fix

my car has been running rich the last few months. sometimes this can be a MAF so I got a new one

replaced spark plugs
rebuilt/cleaned the upper intake manifold
checked all ignition coils
checked all ignition wires
replaced fuel pump
replaced fuel filter
replaced a few breather hoses
checked and cleaned out egr valve. never tested valve with vacuum though
replaced fuel injector o-rings
cleaned fuel injectors
checked o2 sensor functions with a live data obd reader, they all seem to read out fairly reasonable voltage readings
removed cats


but still i get p0151, p0131 especially. and eventually i'll get (if i recall correctly) p0157 and p0137 which means the secondary o2 sensors are also reading too much oxygen. which is weird to me because i built a housing for the secondary sensors OUTSIDE of the exhaust stream, perhaps my housing is leaking in oxygen, but i'm just unsure why i keep getting these errors.

my last idea is an exhaust leak, i see where there is a leak on the upper downpipe, where my exhaust shop never finished welding. maybe this is enough oxygen leaking IN to trip a low voltage code? unsure

StarvingArtist

Don't know what auto tap is, Could it be adding too much resistance to the circuit and tripping the code? These cars are sensitive to wire resistance.

ctravis595

not sure exactly what you mean by auto tap, but yes that is one of my next things to investigate, the o2 sensor wiring and harness into the ECU..

StarvingArtist

OOps, I was answering the first post from 2008. I guess he's figured it out by now.