Knock sensor problem...

[bwh13]

I'm having problems with a rear knock sensor CEL after installing a new VANOS unit. Engine is an S52 converted to OBDI with lightweight flywheel, the 3.5" HFM and 21.5# injectors. An aftermarket computer chip is installed in the DME, tuned for those options. All new sensors, etc.

After the conversion to OBDI, drove car from Oct to May with no issues. Passed AZ IM147 emissions test easily.

Vanos was noisy so had a Dr Vanos unit installed by my local BMW shop. Immediately after (even before getting out of the parking lot) the CEL comes on. They check it with a Peake Research tool; code 45; rear knock sensor.

Since all new sensors were installed during the OBDI conversion, I thought this was odd, but I installed a new knock sensor anyway. Still get the code 45 (or 1226 in BMW code). If I clear the code with a Peake tool, the car will start with no code, but as soon as the RPM goes above 1800 or so the code comes back.

I have installed a stock 325is DME and there is NO CODE, even after driving it around for several days. Re-installed the chipped DME, code is back. Installed new chip from manufacturer, same fault code. It almost appears as if the chipped DME doesn't see the sensor. I can disconnect the sensor, same code at the same 1800 RPM's.

I have tried everything I can think of to determine why this code comes up.

In the 101 Projects book, it states the knock sensor fault code is triggered by "an open circuit, a ground fault, or multiple signals that don't correspond to proper engine operation".

I've checked all the grounds on the harness and engine I can find so I don't that's it.
I don't think it can be an open circuit if the stock DME doesn't show the same code, as it would test for the knock sensor and see if it wasn't in the loop.

What 'multiple signals' is the text referring too? Conflicting signals from sensors or what?