Sure thing! Just make sure to connect into the left input of the LC2i, since the GTO signal sense feature is only present on the left input of the LC2i.
Here are the ways to connect a factory head unit with a mono output:
Add a Sub in Mono
Some aftermarket sub amps only require a mono signal. In that case, use the ‘Left Speaker Input’ on the LC2i and out the ‘Left Bass Output’ to the amp. Note: The GTO signal sense only activates when it is receiving a signal from the ‘Left Speaker Input.’
Add a Stereo Input via Y-Cable
If the sub amp takes a stereo input, use a RCA Y-cable to split the ‘Bass Output’ from the LC2i to the amplifier.
Create a Stereo Input via Jumpers
Install a pair of small jumper wires (short speaker wires) from the left speaker input of the LC2i to the right input to send the signal to both inputs. Make sure the wires are going from positive(+) to positive(+) and negative(-) to negative(-) of the inputs. At that point, you can then connect both the left and right RCA outputs to your amp.