W208 CLK230k. No fault codes ?

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Active Member
Mar 1, 2010
Hi. Just a quick question for the experts here.
Does the ECUs ever become corrupted enough that the car would post no fault codes despite having problems ?
I'm trying to track down a high fuel consumption problem and I just got Autotap an OBDII PC software. What is shows me is that my fuel system is running in perpetual open loop (which should be closed loop when the engine is at normal operating temp). So I changed the temp sensor and fuel regulator. No change, car feels a little torquier but still in open loop.
Then I noticed that the O2 sensor on bank 2 (which I assume is post cat) seems to be constant with little variance - which lead me to order 2 new O2 sensors which I should install by Wed.
My question is : Why aren't any fault codes being thrown up ? Even the star diagnostic didn't pick up any fault codes (let alone my pissy Autotap) . Only reason I can think of is that my ECU may be corrupted. Any comments on how common this is ?


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