Engine knock with both CPS codes and Knock sensor codes

Looking for a little clarity here. I have read as much as I can on this board and others and there seems to be a number of different opinions as to how to solve.

A little history; I have a 2000 740IL and about 4 months ago a CEL popped up and I had it read and it came up CPS. The CEL came on and went off immediately and the engine seemed to be running as usual although I have always had a bit of the rough idle problem that seems to be the case with many of us. Started the car up yesterday morning and heard the " diesel engine " knocking coming from I believe bank 1 ( the right front of the engine ) and after driving the CEL came on and stayed on and the code read for a knock sensor.

The first thing I did was unplug the CPS while the car was running and there was no change in the way the car idled and when I gave it some gas it seemed to be responsive. I have read that this is a indicator that the CPS are bad and that is throwing the knock sensor fault code? Would a bad CPS cause that god awful engine knock? I have also read that there may be back pressure and that pulling the pre-cat O2 sensors and driving it around a bit? The CPS are obviously easy to replace but the knock sensors are a big pain in the rear.

Any input into steps to troubleshoot would be much appreciated.


Happy New Year to all!

Are you running premium fuel? Modern engines use the knock sensors to adjust ignition timing to compensate for lower-octane fuels. That's why it says premium only, but runs fine on regular. Unless, I'm guessing, if your knock sensors go out.

I always use Shell super premium. I also heard the you can unplug the CPS and use an OHM meter and check the resistance? I cant seem to find what the correct reading would be? I am trying to avoid doing all of the work to change the knock sensors if they are not bad. Thamks for your reply, I really do appreciate the help.

There is a lot of discussion on whether ohm-testing the CPSs works. Those who believe it does say the correct reading should be in the hundreds of ohms, and that a bad sensor will read mega- or kilo- ohms. I have also read that the old-style sensors could be ohm-tested, but that the newer sensors on the m62tu cars can't be.

In any case, camshaft position sensors tend to fail gradually. Mine we causing a no-start without throwing any codes. If you saw CPS codes, you should go ahead and replace the sensors. From personal experience, I recommend paying the extra money for true OEM sensors.

Another test you could do, if you think the CPS is bad, is switch the CPSs on bank 1 and bank 2, and see if the knock codes switch to the other bank.