The Mechatronics of the Volkswagen Dual Clutch Transmission
Mostly Volkswagen and Audi cars can have this unique, advanced, dual clutch automatic transmission. They have been around for a few years now and are hailed as an evolutionary step from the traditional transmission. For many, they are either loved or hated- it all depends on whether you had any problems. In 2009, VW recalled 53000 of them for defective mechatronic units.
The mechatronic unit is a computerized control part of the dual clutch system. It is complex and hard to troubleshoot when things go awry. When they do go bad, the dash showing PNDRS will flash and you will basically shut down wherever you are. You may be able to limp home in certain gears or stranded. The mechatronics are housed in the gearbox, surrounded by DSG oil. The mechatronics form the central control unit in the gearbox. All sensor signals and all signals from other control units come together at this point and all actions are initiated and monitored from here. The unit has 12 sensors, By hydraulic means, it controls or regulates eight gear actuators via six pressure modulation valves and five selector valves and it also controls the pressure and flow of cooling oil from both clutches. Temperatures of –40 °C to +150 °C and mechanical vibrations of up to 33 g occur and must be dealt with. The oil temperature is kept from rising above 135 °C by an oil cooler. The gears are selected via selector forks in the same way as a manual gearbox. Two gears are selected by each selector fork. Actuation of the selector forks is hydraulic on the direct shift gearbox and not by means of selector rods.
Many times, the failures begin with sensor temps failing, either outright or falling out of specification. Many have backups and should the main one fail, backup sensors will provide the data to the computer. If the data sent is incorrect, the computer will do what it thinks is right based on that incorrect data, hence, failures. You may only be able to activate or operate in certain gears or none at all is the general result. You may notice grinding or bad fuel economy. Usually, if a sensor fails, only that section impacted by the sensor is effected. So, if a sensor fails for 2nd gear, you will not be able to use that gear.
The sender G509 can be found in the housing of gearbox input speed sender G182.It measures the temperature of the DSG oil at the outlet of the multi-plate clutches. It operates in a temperature range of –55 °C to +180 °C. This is a key sensor. If it fails, the back up sensors may be able to prevent catastrophic loss. If they fail, the tranny will go into self-protect mode and you will be stranded.
If your transmission suddenly starts to shift into odd gears than it normally did or the car stops, it could be the N92 Solenoid valve inside the mechatronics unit which controls activation of all the gears.Below is a list of components in the Mechatronic:
G93 - Gear oil temperature sender, G182 - Gearbox input speed sender
G193 - Hydraulic pressure sender 1, G194 - Hydraulic pressure sender 2
G195 - Gearbox output speed sender 1, G196 - Gearbox output speed sender 2
G487 - Gear actuator travel sensor 1, G488 - Gear actuator travel sensor 2
G489 - Gear actuator travel sensor 3 ,G490 - Gear actuator travel sensor 4
G501 - Speed sender for input shaft 1, G502 - Speed sender for input shaft 2
G509 - Multi-plate clutch oil temperature sender, G510 - Control unit temperature sender
J… - Engine control unit
J329 - Terminal 15 voltage supply relay, J519 - Onboard supply control unit
J527 - Steering column electronics control unit, J587 - Selector lever sensors control unit
J743 - Direct shift gearbox mechatronics, N88 - Solenoid valve 1
N89 - Solenoid valve 2, N90 - Solenoid valve 3, N91 - Solenoid valve 4, N92 - Solenoid valve 5
N110 - Selector lever lock solenoid, N215 - Pressure control valve 1 for automatic gearbox
N216 - Pressure control valve 2 for automatic gearbox, N217 - Pressure control valve 3 for automatic gearbox, N218 - Pressure control valve 4 for automatic gearbox
N233 - Pressure control valve 5 for automatic gearbox, N371 - Pressure control valve 6 for automatic gearbox.
On vehicle diagnosis, testing and information system, use VAS 5051, the following modes of operation: Guided fault finding, Guided functions.
VW has made over 1 million DSG transmissions, most are working fine with no problems as long as the owner maintains changing the fluid every 40,000 miles and properly filling them to the correct level. Costs at garages range from $250-500. The DSG fluid runs $18 per liter, the filter $30. A new mechatronic unit is $4-5000, a new tranny is far worse.