I have a whole bunch of ECUs with knock boards on my floor currently. Decided to do some comparisons...
The OBD0 JDM PR3 and PW0 both have identical knock boards. These boards are marked "AT" or "MT" for an automatic or manual transmission computer, even though these boards are identical between MT and AT versions. There is a port labeled "monitor" that may be useful.
JDM OBD1 PR3(B16 - XSi), USDM P30 (B16 - Del Sol) and USDM P14 (H23 - Prelude Si) all have the same knock board, to the component. The USDM P72 (B18C1) I have uses the same knock board, but adds R11 and R16 to an otherwise identical board. In addition to what appears to be a secondary input/output port(marked "B"), there are also a couple of other interesting looking ports.
Additionally, both the P30 and P72 have R115, R116 and the knock board while lacking R140, R141. The P14 has R118,119 while lacking R142,R143 in a similar position. All P28s, P06 and P74 that I have which lack the knock sensor have R140,R141 while lacking R115,R116. This leads me to believe that the ECU checks for a bit set to use a knock board, and that the knock board could be removed from a ECU by moving R140,141 to R115,R116.
Unfortunately I don't have a 92-95 car to test in. Any volunteers for fiddling with knock board resistors?
[%sig%]