That means the low 4 position switch is sending a signal to the transmission ECU. This means the system is behaving as though pin 7 has been disconnected.
To clarify, when in low range the the shift points move up to a higher RPM. Very much like when you switch to the power mode. If the transmission shifts rapidly through the gears in low range the low 4 position circuit is not working.
If the center will lock using the dash switch but will not lock when shifted into low range the low 4 position indicator is unplugged or there is a problem with the indicator switch or the circuit feeding it.
When you shift into low do the transmission shift points go up? They should if the...