Member
Hey there I am helping a relative with his 2016 BMW M4.
It was sold without the dealer fully going through it because it turns out it had downpipes and tune.
New Cats were put on and a BMW dealer reflashed the computer. But its still is not ready for CA smog. The O2 sensor heater, O2 sensor and Catalyst all remain incomplete.
New O2 sensors have now been replaced with OEM or OE from FCP Euro, but still same problem.
Is there some piggy back thing somewhere that keeps it from having emissions readiness monitors complete?
I have been looking at the downstream O2 sensor voltages to see if I can figure out anything. Also looking at fuel trims.
The car clock keeps getting set back to 24 hr mode, instead of 12 hours mode, which makes me think there is some piggy back thing somewhere resetting something frequently.
Anywhere I should look or something I should test?
Appreciate any help
Senior Member
Supporting Vendor
Could be a few different things, if the piggyback is still connected, it affects the OBD reading.
If you have a piggyback, you will need to remove it
It could also be that you did not do the drive cycle correctly yet. the sensors need sometime to show readiness especially if you just replaced them
and finally, it could be the downpipe. Do you have the stock downpipes now?
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