Hi,
if you are using the MPC5748G EVB, then note the LIN transceiver is not powered from the EVB, thus the transmission will not work, because of bit error (RX pin does not see the same signal that is on TX pin).
So connect 12V to the LIN connector (P11.3 or P9.3)) to power the transceiver. This enables the LIN transceiver to loop TX back to RX so entire transmit frames can be issued successfully.
BR, Petr