Failed Knock sensor? Looking for feedback on severe knock during highway cruise

[lulz_m3]

Helping a buddy with an issue that has been going for a few months now. 2-3 times now he has had a CEL pop for 2E69 "Knock sensor Signal 2" during cruising speeds on the highway. Details and logs below.

2008 535i AT
140k miles
FBO + Meth, protuned on Cobb

Vehicle is well maintained, recently did Walnut blast, HPFP, Fuel-IT Stage 2 LPFP and valve cover gasket. Plugs are newish as are ignition coils. WB o2's are original as are the knock sensors.

Issue occurs maybe once per month, vehicle is driven daily with LOTS of highway miles.

http://www.datazap.me/u/lulzm3/1?log...18-19-20-21-22

http://www.datazap.me/u/lulzm3/1?log...18-19-20-21-22

My current thoughts: Swap his knock sensors with mine and see if the problem follows the sensors. Car runs great outside of this sporadic issue. I have another theory that during o2 sensor calibration it could be going extremely lean and causing actual knock during lean cruise conditions, but that seems like a bit of a stretch.

Would love to hear some feedback from the guru's if you have an experience.

[George@BMS]

Not sure what the cause is but be sure to torque them to spec. I have seen over tightened knock sensors cause all sort of issues on other models

[bradsm87]

The weird thing is that it happens on both front and rear banks which use separate knock sensors. I don't really know what I'd do to be honest. Being Cobb pro tuned means your map is probably locked so makes it hard to diagnose if it's tune-related.

Maybe reset all adaptations?

[quing]

Did Op ever find out the problem?

[dmacpro91]

2E69 was my engine breaker. I developed a 2E69 one day and the first step was to replace the knock sensor. Didn't fix it so I replaced it with another knock sensor just in case that one was also bad. Still didn't fix it. We did a compression test and found that cylinder 3 had half the compression of the other cylinders. I replaced the engine and now everything is working well again.

Symptom was that the car would throw the 2E69 anytime the engine speed rose above ~3000 rpm.

[lulz_m3]

Did Op ever find out the problem?

No, but he resolved it by replacing the E60 with a LCI 550 M sport