Originally Posted by
tonyford
PTU=Power Transistor Unit. It's located under your ignition coils. It drives the coils.
What's this got to do with the the transfer case?
PTU=Power Transfer Unit, it's the gearbox on the passenger side of the transaxle that turns the driveshaft.
A transfer case like used in a real 4WD normally had it's own gear ratio like low and sometimes a differential that could be locked when needed like in full time four wheel drive system. Some just had a locked high and low position.
Coil on plug(COP) has been used for years and all the drivers are in the PCM. Even before COP, drivers were in the PCM since like late ninties. Not sure when they went to COP.