Replacement intelligent servo module (shift selector unit) for the Mercedes 722.9 7G-Tronic, OE A0002701752 and A0002701852. Needs coding after install.
If your Mercedes with a column-stalk or push-button Park shifter is stuck in Park, shows "Drive to workshop without changing gear," or lets you pick D or R on the stalk while the transmission never actually moves, the part people end up searching for is the intelligent servo module, or ISM. This replacement module is for the 722.9 7G-Tronic and references OE numbers A0002701752 and A0002701852. It is listed for 722.9 cars with the DIRECT SELECT shifter, including the W212 E-Class, W164 M-Class, X164 GL, X166 GL/GLS, W251 R-Class, CLS and S-Class coupe.
On a DIRECT SELECT car there is no cable between the shifter and the transmission. The stalk on the steering column (or the console lever with a Park button) is only an electrical switch. The ISM, Mercedes component A80, is bolted to the outside of the transmission housing and does the mechanical work. Mercedes-Benz StarTuned describes how it works: a main motor turns a screw shaft through a toothed belt (earlier versions used gears), a slide nut on that screw moves the selector lever on the transmission into P, R, N or D, and a sensor reports the actual lever position back. The module gets its commands over the engine CAN bus.
It is also a security part. The ISM belongs to the Drive Authorization System, so it will not move the selector until the key, the electronic ignition switch (N73), the engine control module and the transmission control unit have all exchanged their encrypted handshake. If something goes wrong, the ignition switch can trigger the Emergency-P function: a second small motor releases the slide nut and a spring forces the lever into Park. That motor cannot be reversed from outside the module. The car stays in Park until the cause is fixed.
Most stuck-in-Park complaints on these cars are not a bad module. Mercedes service information for 722.9 vans with the A80 module lists the causes in order: undervoltage of the main battery, undervoltage of the separate Emergency-P battery, a power supply fault to the ISM, and only then an internal ISM fault, confirmed by a P179Cxx code. On the X166 GL/GLS and M-Class, a Mercedes bulletin covers code B226600, "drive authorization data are implausible," logged in the shift module after cold soaks. The fix there was a new starter battery, and Mercedes noted the old battery would still pass a conductance test. So test the main battery under load, check the small Emergency-P or auxiliary battery if your car has one, and measure supply voltage at the ISM connector with it plugged in.
StarTuned also recommends checking the CAN-C wires: each should read roughly 2.4 to 2.6 volts DC to ground. A wire at 0 V is shorted to ground and one near 12 V is shorted to power. Our 722.9 no-movement diagnosis guide walks through separating a Park lockout from a true internal no-drive, and the 722.9 limp mode causes guide covers the faults that look similar from the driver's seat. Buy the module once voltage, wiring and CAN checks are clean and the scan tool points at A80 itself.
This module is listed for 722.9 7G-Tronic cars with DIRECT SELECT: W212 E-Class, W164 M-Class, X164 GL, X166 GL/GLS, W251 R-Class, CLS and S-Class coupe. Cars with a conventional mechanical shift lever and cable do not use an ISM. Mercedes revised this part over its production run, so read the number printed on the label of your old module and match it to A0002701752 or A0002701852 before ordering. If the label is unreadable, send us your year and VIN and we will check it. Other 722.9 parts are on our 722.6 and 722.9 parts page.
If the car also shifts harshly or flares once it is moving again, that is a separate hydraulic issue. A fresh 722.9 service kit with ATF and filter is the place to start, and our 722.9 common problems guide covers the next steps.
| OE numbers | A0002701752, A0002701852 |
| Transmission | Mercedes 722.9 7G-Tronic |
| Listed vehicles | E-Class W212, M-Class W164, GL X164, GLS X166, R-Class W251, CLS, S-Class coupe |
| Programming | SCN coding / initialization required after install |
| Weight | 3.48 lb |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is listed for 722.9 7G-Tronic cars with the DIRECT SELECT shifter: W212 E-Class, W164 M-Class, X164 GL, X166 GL/GLS, W251 R-Class, CLS and S-Class coupe. Match the number on your old module to A0002701752 or A0002701852, or send us your year and VIN and we will confirm.
Yes. The ISM is part of the Drive Authorization System and is a theft-relevant part, so it must be coded to the vehicle and have its Park position taught before it will shift. You need a Mercedes-capable scan tool or a shop that can do the coding.
Usually not. Mercedes lists main battery undervoltage, Emergency-P battery undervoltage and ISM power supply faults ahead of an internal module failure. Load-test the batteries and check supply voltage and the CAN wires first. An internal fault is indicated by code P179Cxx.
No. The module bolts to the outside of the transmission and works the selector lever, so the hydraulic side stays sealed. You only unplug the connector, unbolt the module and fit the new one.
Restoring battery voltage often releases it. If it does not, Mercedes diagnostic software can put the transmission in Neutral so the car can be moved into a bay. The Emergency-P motor inside the module cannot be reversed by hand.
