ricoh 2238c yellow won't print

[SOCPWB]

we got a message "SC387" for a while, we were trying to set auto color cellecttion/full color mode to B&W mode but it doesn't accept still change back to auto mode cellection/full color.

we change new toner cartridge and new developer unit for yellow, the machine still won't print yellow out, we're really discouraged about this problem always comes out, is anyone any resolutions like pump, toner pipe, any parts cleaned not properly?

please help! thanks a lot!!