DSM · ISM
Parking lock or gears acting up? Often it’s the DSM.
The Direct Select Module (DSM) – formerly called Intelligent Servo Module (ISM) – sits on the gearbox and engages the selected gear, including the parking lock. We repair your original module.
Typical symptoms
- Parking lock won’t engage or won’t release
- Gear is engaged with a delay or not at all
- “P not possible” message or transmission warning
- Whirring or clunking at the gearbox when shifting
- Fault codes for the DSM/ISM or parking lock
What causes it?
The DSM consists of an electric motor, a small gear drive and its own electronics. It sits low down on the gearbox and is exposed to heat, moisture and dirt. Wear, corrosion and ageing components are typical causes.
The electronic selector lever module (EWM), which detects the selector position, can cause similar symptoms. We test both and only repair the part that is really faulty.
Focus on Mercedes-Benz. AEZ is an independent master workshop; brand names are used for description only. We tell you whether a repair is possible after testing.
How the repair works.
- 1
Get in touch
Vehicle, VIN and what happened – via WhatsApp, phone or form.
- 2
Drop off or send in
Hand it in at Bottrop or, after a quick chat, send it by DHL. How shipping works
- 3
Test, price, repair
You get the findings and price before we repair. Then the unit goes back to you.
Frequently asked questions
Is DSM the same as ISM?
Yes. DSM (Direct Select Module) is the newer name for the former ISM (Intelligent Servo Module). Not to be confused with the EWM, the electronic selector lever module.
Can I keep driving with a faulty DSM?
We advise against it. If the parking lock doesn’t engage reliably, the vehicle can roll away. Always apply the parking brake and have the fault checked soon.
How much does the repair cost?
That depends on the unit and the fault. After testing we tell you the price – we only repair with your approval.
Can I send the control unit in?
Yes. After a quick chat, by DHL to AEZ, Werkstraße 4, 46240 Bottrop, Germany. Packing tips and the shipping note to fill in are on the “Sending in a control unit” page.
Do you only work on Mercedes-Benz?
Our focus is Mercedes-Benz. For other makes, just ask with the vehicle and part number – we’ll tell you honestly whether we can help.