Drive to Workshop Without Shifting Gear – ISM Failure on Mercedes-Benz Vehicles
Is the Drive to Workshop Without Changing Gear message appearing on your Mercedes-Benz Dashboard? Learn the cause of why the warning light is illuminating and how to use the YOUCANIC Full System scanner to confirm the problem.
Mercedes-Benz owners may get an error message on the dashboard stating, “Drive to Workshop without changing gear.” due to the Intelligent Servo Module (ISM) failure or DSM if it is a newer version. The most common problem that causes a Drive to Workshop Without Changing Gears or the Service Required Do Not Shift Gears message on a Mercedes-Benz is a faulty Intelligent Servo Module (ISM), also known as component A80.
On newer Mercedes-Benz models, ISM is called DSM. The DSM module is manufactured by Continental and is printed on the module’s sticker. In the older models, all Mercedes-Benz vehicles had a mechanical link between the shifter and transmission; that’s no longer the case for models equipped with the 7-speed and 9-speed automatic transmissions.
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Mercedes-Benz vehicles with the gear selector mounted on the steering column (behind the steering wheel) no longer have a mechanical link to the transmission.
Around 2005, Mercedes-Benz introduced the 722.9 New Automatic Gearbox 2 (NAG2) automatic transmission, which no longer has a mechanical link between the shifter and transmission. This is known as drive-by-wire technology.
You select gears electronically instead of a mechanical link from the shifter lever to the transmission. The Intelligent Servo Module (A80) or ISM does the physical work of changing the transmission gear position.
If the ISM is defective and you turn off the engine and try to restart the car, you may get stuck on the side of the road (or in a parking lot) because the engine will not start if it can no longer detect the transmission in the Park position.
When the ISM module fails, your Mercedes-Benz will not shift gears between P, R, N, and D. Also, the current gear no longer gets highlighted on the instrument cluster.
Replacing the ISM unit at the dealership can be very expensive. The cheaper solution is to remove and fix your existing ISM module.
Don’t expect a Mercedes-Benz dealer to repair your existing ISM or install a used one. Dealerships will only replace faulty ISMs with new units. You may even be told that a used ISM module is “married” to the car and can not be reused, but that is no longer true, as many specialized auto repair shops can make a used ISM “virgin” and pair it to another vehicle.
If you decide to fix your faulty ISM module, you must raise the vehicle to remove the module mounted on the side of the transmission housing. ISM module is mounted on the outside of the transmission, so the transmission itself does not need to come off.
ISM can then be sent to a Mercedes-Benz specialist who will repair or flash your VIN. You can find several Mercedes-Benz specialists on eBay that offer Mercedes-Benz ISM Flash / Repair Service. Even though this error means a faulty ISM module, we recommend reading the fault codes with a Mercedes-Benz scanner or having an auto mechanic diagnose the vehicle to confirm the ISM is defective.
Symptoms
First, let’s take a look at common symptoms of a defective ISM module, include
- The car won’t shift gears—no P, R, N, D.
- The vehicle may not start, and no crank-. The ISM (intelligent servo module) controls the transmission gear position. It will prevent the car from turning over if it does not recognize that it is in Park on Neutral.
- Drive to the workshop without selecting gear on the dashboard
- The car would not change gears.
- Error message: The actuator motor in the component A80 ISM (Intelligent Servo Module) for Direct Select cannot reach its target position.
- The shifter becomes unresponsive.
- The engine runs at high rpm.
- Error communicating with Actuator Motor A80 of Intelligent Servo Module
- Service Required: Do Not Shift Gears; visit the Dealer.
These problems can be caused due to either ISM software issues or hardware failures.
Fault Codes
Common fault codes are triggered by a faulty Intelligent Servo Module (ISM A80).
- 1994 – Component A80 Direct Select Defective / Can not reach the specific gear target position
- 1984 Unkown fault code, Unknown fault code Unknown fault type: -1
- 5399 ESP CAN Signal Gear Selected from N15/3 implausible
- C103-ETC No CAN Message Received from A80 (Intelligent Servo Module) for direct selection.
- Error code: 1994 Description: Component A80 ( Intelligent Servo Module for Direct Select) is defective
- 1974 selector lever position P was engaged due to a fault occurring in component a80 (intelligent servo module for DIRECT SELECT) or the vehicle communications
- 1922 System Shut down due to an internal Fault
- 1904 The internal mechanism in component A80 for engaging select or lever position P is not in the correct position.
The best way to determine what is wrong is to have your mechanic or yourself scan the ISM with an advanced Mercedes-Benz scanner.
How to Diagnose ISM Unit
To diagnose Mercedes-Benz ISM, you will need a YOUCANIC full system scanner.
- Connect your scanner to the diagnostic port under the dashboard.
- Allow your scanner to turn on.
- Select Mercedes-Benz, then your Model.
- Select Control Units
- Select Chassis
- Select the ISM – Intelligent servo module for Direct Select.
- Once you enter the ISM module, you will be able to:
- View software/hardware version
- Read Fault Codes
- Clear Fault Codes
- Data Stream
- Activation – Move transmission into a Neutral Position.
When you scan the ISM module, you will get fault codes such as 1994 – Component A80 (intelligent servo module for Direct Select), which is defective. Once you scan the codes, you will better understand why your Mercedes-Benz won’t drive or is stuck in the park. Inspect all the control units to ensure no other issues are present. If your Mercedes-Benz has a defective ISM module, it must be repaired or replaced.
If you try to read the fault codes from the ISM and get a No Communication error, this is a sign that the ISM is defective.
Where to Repair Mercedes-Benz ISM Module?
Is it possible to repair your existing ISM module? Repairing or flashing a used ISM module is much cheaper than replacing it. You must remove the ISM module from the vehicle and ship it to a vendor that offers ISM module repair.
A technician repairs your ISM module and ships it back. The turnaround time ranges from 5 to 12 days, depending on your location and chosen service provider. In addition to the low cost, another advantage of repairing your ISM module is that it will not need SCN coding. SCN coding is required when you install a new ISM module. During SCN coding, the VIN is permanently coded to the ISM module.
You will still need a professional scanner to carry the initial adaptation, known as the Selection Sensor Adaptation procedure. This can be done with MB Star Diagnostic Tool or professional-level scanners. Keep in mind that some modules can not be repaired. You cannot know if your damaged ISM module can be fixed until the technician tests it or if you try to read the ISM fault codes with the YOUCANIC scanner and see if the ISM will read codes and show live data. Suppose the ISM is not responding, showing any communication error, or if live data can not be retrieved from the old unit.
Generally speaking, ISM or DSM modules that show these fault codes can be repaired:
- Error: 1984; Description: Uknown fault code Unknown Fault Type: -1
- Error1994; Description: Component A80 ( Intelligent Servo Module for Direct Select) is defective
- Error 1904 – cannot be cleared.
How much does replacing an ISM module at a Mercedes-Benz dealership cost?
Any Mercedes-Benz dealership or an independent mechanic specializing in Mercedes-Benz cars can replace your ISM or DSM. However, replacing the ISM can be an expensive repair. You will spend anywhere from $1200-$1900 to replace and program the ISM at the dealership or repair shop.
If you use an independent mechanic, they must order the ISM module from Mercedes-Benz. You will need to provide proof of vehicle ownership and identification, as Mercedes-Benz requires this information. Once the order is approved, the mechanic receives the ISM Module. The module will need to be replaced, and it will also have to be programmed with a professional scanner.
How much does it cost to fix the Mercedes-Benz drive to the workshop without changing the gears problem?
Fixing the drive to the workshop without a chaining gears issue on a Mercedes-Benz can be expensive, but it doesn’t have to cost thousands of dollars, as would be the case if you went to the dealership.
The least expensive way to fix the problem is to purchase an aftermarket ISM or DSM module. You can get the module replaced and coded for less than $900. You will spend $300 for the module, $300-$400 to replace it, and another $200-$300 to code it to the vehicle. Call independent shops in your area specializing in Mercedes-Benz cars, as most auto repair shops won’t be familiar with this problem or solution.
Where is the ISM module located?
The intelligent servo module for DIRECT SELECT is mounted on the left side of the transmission housing (driver side for LHD). The vehicle must be raised to access the ISM module, but the transmission must not be removed.
Another look at the ISM module with the engine and transmission still in the vehicle.
ISM Communication
ISM module receives input from the gear selector. ISM also communicates via C.A.N. with the following modules.
- The instrument cluster (A1)
- ESP control unit (N47-5) – Vehicle speed input. Needed to P release or D engage.
- EIS [EZS] control unit (N73) – Input from EIS automatically switches the vehicle into P when the car is turned off.
- Steering column module (N80)
- The central gateway control unit (N93)
- Fully integrated transmission control (VGS) control unit (Y3/8n4)
For example, vehicle speed input is needed to engage D or release Park and is received from the ESP module. When the vehicle is turned off, information is required to automatically switch the transmission to Park, as provided by the EIS.
Which Mercedes-Benz vehicles have the Intelligent Servo Module (ISM)?
Mercedes Intelligent Servo Module (ISM) was installed in 2005, and newer vehicles are equipped with the 7G Tronic Transmission (Code: 722.9) and gear selector mounted on the steering column, except for a few 2005 to 2007 models that still use the 5-speed 722.6 transmissions.
All 2006 and newer vehicles with 7-speed transmission 722.9 have an ISM module.
| MODEL | YEARS | COUNTRY | TRANS TYPE | ENGINE TYPE/SIZE | TRANS MODEL |
|---|---|---|---|---|---|
| MERCEDES A CLASS | 00-11 | CHN EGY DEU MYS ZAF VNM | 7 SP R/AWD | L4 2.2L V6 2.5L 3.0L 3.5L V8 6.3L | W7A700 |
| MERCEDES A CLASS | 11-Jul | EGY | 7 SP R/AWD | V6 3.0L V8 6.3L | W7B700 |
| MERCEDES A CLASS | 11-Jul | EGY DEU VNM | 7 SP R/AWD | V6 2.5L 3.0L 3.5L | W7X550 |
| MERCEDES CL | 11-Mar | DEU | 7 SP R/AWD | V8 5.0L 5.5L 6.3L | W7A700 |
| MERCEDES CLC | 11-Aug | BRA | 7 SP RWD | V6 2.5L 3.5L | W7A700 |
| MERCEDES CLK | 9-Apr | DEU | 7 SP RWD | V6 2.5L 3.0L 3.5L V8 5.0L 5.5L 6.3L | W7A700 |
| MERCEDES CLS | 11-Apr | DEU | 7 SP R/AWD | V6 3.0L 3.5L V8 4.6L 5.0L 5.4L 5.5L 6.3L | W7A700 |
| MERCEDES CLS | 11-Oct | DEU | 7 SP RWD | V8 6.3L | W7B700 |
| MERCEDES E CLASS | 11-Feb | CHN EGY DEU IND IRN MYS THA VNM | 7 SP R/AWD | L4 2.2L V6 2.5L 2.6L 3.0L 3.5L V8 4.0L 5.0L | W7A700 |
| MERCEDES E CLASS | 11-Sep | DEU | 7 SP RWD | V8 5.5L 6.3L | W7B700 |
| MERCEDES E CLASS | 11-Sep | DEU | 7 SP R/AWD | V6 3.0L 3.5L V8 5.5L | W7X550 |
| MERCEDES G WAGON | 11-Jun | AUT | 7 SP AWD | V6 3.0L V8 4.0L 4.6L 5.5L | W7A700 |
| MERCEDES GL CLASS | 11-Jun | USA | 7 SP AWD | V6 3.0L V8 4.0L 4.6L 5.5L | W7A700 |
| MERCEDES GLK | 11-Aug | DEU | 7 SP R/AWD | L4 2.2L V6 3.0L 3.5L | W7X550 |
| MERCEDES GLK | 11-Sep | DEU | 7 SP R/AWD | V6 3.0L | W7A700 |
| MERCEDES ML CLASS | 11-May | USA | 7 SP R/AWD | V6 3.0L 3.5L V8 4.0L 4.6L 5.0L 5.5L 6.3L | W7A700 |
| MERCEDES R CLASS | 11-May | USA | 7 SP R/AWD | V6 3.0L 3.5L V8 4.6L 5.0L 5.5L | W7A700 |
| MERCEDES S CLASS | 11-May | EGY DEU IND IDN MYS THA | 7 SP R/AWD | L4 2.2L V6 3.0L 3.5L V8 4.0L 4.3L 4.6L 5.5L | W7A700 |
| MERCEDES S CLASS | 11-Jun | DEU | 7 SP R/AWD | V6 3.0L 3.5L V8 4.6L 5.5L | W7X550 |
| MERCEDES SL | 11-May | DEU | 7 SP R/AWD | V6 3.0L 3.5L V8 5.0L 5.5L | W7A700 |
| MERCEDES SL | 11-Jul | DEU | 7 SP R/AWD | V8 6.3L | W7B700 |
| MERCEDES SLK | 11-May | DEU | 7 SP R/AWD | L4 1.8L 2.2L V6 3.0L 3.5L V8 5.4L 5.5L | W7A700 |
| SSANGYONG CHAIRMAN | 11-Aug | PRK | 7 SP R/AWD | V6 3.2L 3.6L V8 5.0L | W7A700 |
Can I install a used ISM?
An ISM module is locked to a vehicle. You cannot remove a used ISM, install it in your car, and expect it to work without coding. The only way to get a used ISM to work on your Mercedes-Benz is to find a third party to program the ISM Module. This procedure may be referred to as flashing ISM or as ISM RENEW.
During ISM flashing, the old VIN is erased from the ISM. Thus, the ISM is made virgin, and your vehicle’s VIN is coded to the used ISM. Several vendors offer Mercedes ISM Renew service. Mercedes-Benz dealerships do not install used Mercedes-Benz ISM modules.
We hope you find the Drive to Workshop Without Shifting Gear – ISM Failure Mercedes-Benz guides helpful. Check these troubleshooting and repair guides for more help on your Mercedes-Benz.
