Common Faults in the 6-Speed DSG Automatic Transmission
The transverse 6 speed DSG transmission, also known as DQ250, is a dual clutch automatic transmission that is found in vehicles by a number of manufacturers. These manufacturers include Audi, Volkswagen, Skoda, and Seat. Like the Powershift transmission I recently wrote about, the DQ250 is a dual clutch transmission that employs a combination of manual transmission gears and automatic transmission clutches in order to gain the benefits of both.
This particular transmission is old news, having been replaced by newer versions, but it has been used in so many vehicles that are still on the road today that it is most definitely still relevant.
So, what happens when this very popular transmission goes bad?
How the DSG Transmission Works
To defeat your enemy, you must understand your enemy. So it is with transmission faults.
Before we get into the faults, we’ll briefly touch on how the DSG transmission works, and how it’s different from other transmissions.
A traditional automatic transmission uses a number of clutch packs to produce the desired output ratio. This works fine, but it has drawbacks, one of the biggest being fuel efficiency. Conversely, manual transmissions use solid metal gears and a single manually operated clutch. This setup creates less resistance and better fuel efficiency, but it means the driver has to deal with pesky clutch pedals and gear levers.
DSG 6 Speed Demonstration
DSG stands for Direct-Shift Gearbox, and it incorporates the best of both worlds into its design. Using an advanced electro-hydraulic control module to control clutch application and gear shifting, the DSG is able to bring the driving comfort of a full automatic to the table while still getting the greater efficiency of the manual-style gears. Furthermore, it makes use of a dual clutch assembly, where one clutch is responsible for even numbered gears and the other for odd numbered gears, improving shifting quality further.
It’s important to note that this article is concerned specifically with the DQ250 variant of DSG transmission. There are other variants, such as the 7 speed DQ200, and the inline 0B5 transmission.
DSG (DQ250) Common Faults
The most common faults I have experienced with this particular transmission.
Before we get into the transmission fault here, there is another cause of juddering which is far more common, and it is outside of the transmission itself. If you experience the juddering mainly when you start the engine and when the car is idling, often accompanied by a loud clattering noise, the problem is likely in the dual mass flywheel which sits between the transmission and the engine. The flywheel consists of two plates that can move a small amount in relation to each other. This provides a cushioning effect when torque is transferred from the engine to the transmission. When that flywheel wears down and the amount of movement is too great, you get a juddering/shuddering sensation.
It’s important not to leave this fault for too long. If the two flywheel plates sheer off from each other, your vehicle will lose drive entirely.
If your flywheel is fine, however, and the juddering sensation is most noticeable on gearshifts—particularly at lower speeds—the problem likely lies in the dual clutch assembly. Unfortunately it’s a simple matter of wear and tear, and there’s not much to be done for it other than replace it.
There are kits available that allow for the replacement of many of the components of the clutch assembly, and oftentimes that will cure the fault. However sometimes the wear and tear is in the non-replaceable components, and a new assembly is needed. In my experience it’s much more practical to just replace the whole assembly. You might save money by getting a repair kit rather than a clutch, but if the damage ends up being in the non-replaceable components, you’ll still need to buy a complete assembly and that money saved becomes money wasted.
Default Mode—also known as limp mode and failsafe mode—is a failure state of the transmission where it detects a fault and limits itself to one gear (typically third) to limit damage to the transmission. This will often be accompanied by an indicator on the dashboard, such as flashing “PRNDS” lights. If your transmission has gone into default, there will be trouble codes in there to explain why it’s done this. You’ll need to get your vehicle scanned with a good diagnostic machine to find out what those codes are.
If the codes mention “clutch limits reached” (or something similar), there’s a good chance the problem is your clutch. Typically (though not always) this won’t occur until after the aforementioned juddering/shuddering fault. If the codes mention “adaptations”, it’s possible that your problem may be fixed with an adaptation reset. You’ll need to find someone with a good VAG diagnostic tool for this.
If the codes mention any sensors, gear ratios, or unexpected mechanical disengagements, the problem is almost certainly your mechatronic. The mechatronic is the name given to the electro-hydraulic control unit that is responsible for controlling the gearbox, and it’s a very expensive lump. Fortunately, there are many companies that can repair this fault, and a quick search of “DSG Mechatronic Repair” should yield plenty of results. It should be noted, however, that these companies are limited in what they can test for and repair in these mechatronic units. I have been involved in a number of situations where the mechatronic was tested by the repair company and found to be “ok”, yet the fault was eventually cured with a replacement mechatronic. Bear in mind, with these repair companies, “tested ok” means they couldn’t find a fault. Not that there’s nothing wrong with it.
One particularly common symptom of a faulty DQ250 mechatronic is a partial or total loss of reverse, so be on the lookout for that as a strong indicator that the mechatronic is failing.
The mechanical workings of the DSG—the physical gears and syncros—don’t tend to fail very often in my experience. I have seen a number of instances of bearings wearing down, however. This typically results in a metallic noise when driving.
I have known DSG transmissions with this symptom to be driven for quite some time with no ill-effects other than quite irritating driving noise, however I most definitely wouldn’t recommend you leave this problem unattended. If the mechanical components of the DSG did fail, it would be pretty catastrophic for the transmission.
The fix is a bearing kit, assuming the problem is dealt with promptly and no other damage has been caused.
One or two other useful bits of information about DSG transmission faults.
Five Things You Shouldn't Do With a Dual Clutch Transmission
It’s also worth noting that, on occasion, a simple adaptation reset can fix a number of minor issues, such as poor shifting quality. Adaptations are little adjustments that your mechatronic makes to things like how much pressure it applies to the clutches to compensate for wear and tear or driving style. Sometimes things can get a little out of whack, and in those cases a reset of the adaptation values—followed by a proper drive cycle—can sometimes be enough to clear the issues up.
One fault I have seen a few times in DSG vehicles is the loss of ability to start the vehicle, accompanied by a fault code relating to the park/neutral switch. The problem is that the mechatronic is getting bad information regarding the position of the gear selector, and won’t let you start the car because it can’t be sure you are in park or neutral. The affected part here is actually in the gear selector itself, rather than the transmission. Though it could also be a wiring or communication fault.
And that’s the end of my 6 speed DSG faults hub. I hope you found this information helpful, and if you have anything to ask—or add!—please drop a comment below.