Mercedes-Benz 642 900 78 01 is a glow plug control module/relay for the OM642 3.0 V6 diesel. It is a 6-cylinder module.
It is used on OM642 applications including:
E-Class W211 / W212 — E280 CDI, E300 CDI, E320 CDI, E350 CDI
M-Class W164 — ML280/320/350 CDI
GL-Class X164 — GL320/350 CDI
S-Class W221 — S320/S350 CDI
Other Mercedes models fitted with the OM642 V6 diesel.