Pololu QTR-8RC - Manual (Page 11)

If you are operating at a Vcc of 3.3 V, short those two pins together with a piece of wire. With a connection in place
between these two pins, the two-sensor board will function.
After the separation, sensor outputs 7 and 8 on the six-sensor board will no longer provide any signals.
QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation
6. Breaking into Two Submodules Page 11 of 12