Oops! You pulled the battery cable without attaching a battery backup, and you just know you’re going to see the “CODE” message on the radio panel when you reconnect.

Better hope that customer has the code information, such as this card, in his or her papers somewhere. If not, you’ll need to present proof of who actually owns the car and your own credentials before the company will release the unlock sequence.

Well, there’s good news and bad news.  First, none of the radios Mercedes-Benz has used for years will lose their station settings from a power interrupt, so the customer won’t have to tune or seek until he finds his favorite disk jockeys, classical music stations, or talk shows, then reset those buttons.  But no matter how fast you might be at realizing what you’ve done and slapping that cable back on the terminal, you’re going to have to reset the code.  This function occurs in milliseconds. Rumors you may have heard about internal batteries or lingering capacitance holding this useful feature at bay for any length of time at all are simply false.  You’ll have to just accept it, then follow through with what must be done to make that radio operational again.

The radio will inform you of your mistake with the alarm display, “CODE.” After you’re done slapping your forehead, what do you do to set things right and stay in your patron’s good graces?  Well, resetting the radio is done in different ways for the various audio systems found in Mercedes-Benz cars, and here’s the information you’ll need to perform the procedure on some common models.

One note up front:  Carmakers first installed radio anti-theft systems to thwart felons and bandits who ripped radios from cars, leaving gaping holes in ruined dashboards. With anti-theft systems, this enterprise fails because such a filch renders the radio useless, and although junkies may wallow in delusion with the shrieking gibbers, drug pushers and fencers of stolen property do not.  No way they’re going to pay anything for even the most upscale unit if it can’t be used because the thief neglected to get the code card along with it (that’s why M-B advises that the card should not be kept in the glove compartment, although after the owner takes it out and puts it somewhere among his or her other papers, there’s a good chance that he or she won’t be able to find it again, human nature being what it is). Nothing in this article serves to get around that anti-theft feature. If you don’t have the specific radio code for this vehicle, either from the car owner’s records or directly from Mercedes-Benz’s C.A.C. (Customer Assistance Center), you won ’t find it here, either, or any way to work around it.

If your customer doesn’t have the radio-code information, you’ll find that the company’s representatives will want a fair amount of proof of who owns the car and who is doing the work before they’ll release the unlock sequence.  In some cases, MBUSA may require that you take the car to a dealership to confirm all the vehicle information first. Considering that the whole point of this system is to make things inconvenient, if not impossible, for thieves, you can understand why.

Mercedes-Benz builds cars, not radios, so there are different radios in different cars, depending on the model year, the accessory choices and so on. Different radios use different release code procedures, so make sure you know which radio you have before you start. You won’t destroy the radio by punching the code in the wrong way, but you could trigger a second level of defense, requiring a longer or shorter wait depending on how often you’ve flubbed the procedure. This second level of defense could require leaving the radio turned on (but non-functionally locked) for as long as 24 hours. The point, again, is to discourage and dishearten those who believe in helping themselves to others’ property.

Radios from different suppliers have different release code procedures. If you try the wrong one, you might trigger a second level of defence, which may entail a long wait.

Unlocking the CODE

Start with the model year in our boxes below.  Make sure the radio faceplate in our line drawing corresponds to the radio in the car, and follow the instructions exactly. Many different radios use slightly different unlocking procedures, and you must use the exactly correct one for that radio.

For earlier models, you may recall that there were some “gray-market” cars with European radios, none of which is included here. For them, you’ll have to go to your local dealer (who may not be entirely ecstatic about the job, either). The first generation of anti-theft radios to appear in Mercedes-Benz cars were the Beckers used from 1986 to 1989. If one of these early units requires digital unlocking, you’ll definitely have to take it to an M-B dealer because a physical electronic key is required to unlock them, and these keys are not generally available.

Avoiding the situation

Of course, you’d be better off if you didn’t cause this sometimes-frustrating glitch in the first place.  So, whenever you’re about to disconnect a Benz’s battery for whatever reason, stop and think. All you have to do is attach an auxiliary power source to the cables.  We used to keep a small motorcycle battery around for the purpose, but now we just use our portable jump-start box.  There’s even a special tool available called a “Memory Retainer.” By the way, if you plug the auxiliary into the cigarette lighter, remember that you’ll have to leave the key on to keep Circuit 15 alive.

Procedures for Selected Models