Hi all!Reading this forum for years, posting for the first time.
As the title says, I’m currently working on reviving a 2003 Mercedes-Benz SL500 that I purchased from Facebook Marketplace. On December 31st, 2024, I bought a non-running R230 from a private seller who apparently damaged most of the car’s electronics while attempting DIY projects. (If I had known everything that was wrong with it, I probably would’ve walked away.) Once the car was delivered to my garage, I spent several days trying to figure out what was wrong and whether it could even run again. I had to rely on the seller’s word that it had been running before. Eventually, I discovered that two of the main fuses — a 100-amp and a 50-amp — were blown, along with several smaller fuses in the rear fuse box. I replaced them all, but the car still wouldn’t start. Some electronics came back to life, but that was about it. When I tried connecting Xentry to scan the modules, I realized the ECU and EIS weren’t showing up, so I assumed they were fried. I ordered a used ECU, EIS with keys, and a shifter from eBay. Once those arrived and were installed, the car started right up. That was a huge relief! I even took it for a short test drive around the block and everything — including the ABC system — seemed to work perfectly. Feeling motivated, I moved forward with the project. I ordered all the interior parts the previous owner had broken (he clearly had no clue how to work on a Mercedes — every plastic clip on the dash and gloveboxes was snapped). I also bought new seats and parts to repair the hydraulic system for the convertible top. Fast forward three months, and I’ve fixed everything that was broken. The car starts, runs well, and the convertible top works like new. But… I still have a few issues that I just can’t figure out, and I’m hoping someone here can point me in the right direction. My car originally has 58K miles, but since I had to replace the ECU and EIS, the instrument cluster isn’t showing the mileage anymore. The replacement ECU and EIS have 35K miles stored and are still coded to the VIN of the donor vehicle. Also, even though I have two keys, neither of them can lock or unlock the car remotely. The central locking system doesn’t seem to recognize the keys, although the lock/unlock buttons on the dashboard work fine (and yes, the vacuum pump is working). At this point, I’m stuck. Xentry can’t change VIN numbers in non-virgin modules and can’t sync the cluster with the new EIS. I’m looking for someone who might be able to help with this — either a professional who can do the work or advice on how to fix it myself (if that’s even possible). I’ve already invested a lot into this car and would really prefer not to give up on it. I’m a huge fan of older MBs — I currently own two W208s (a 430 and a 55) and two W219s (a 500 and a 550) — and I’d love to add this R230 to the collection. Thanks in advance for any help!

 

You have a few options.

Option 1 is to just virginize the cluster and relearn it to the EIS. The EEPROM needs to be removed, reprogrammed, and reinstalled. This will probably run a couple hundred from a Mercedes electronics specialist. Mileage will start at the 35K of the new EIS. so you will not have actual mileage, but you will at least have a readout.

Option 2 is to revert to your original immobilizer components, replacing, repairing, or cloning as necessary. I would start by having both the ECU and EIS evaluated to see if they are repairable. The ECU is relatively easy to virginize, so either a repair of the old one or virginizing the replacement one will work. The EIS, especially if both are early dual processor versions, is a bit more of an issue. Repair is the best option, but if it cannot be repaired, you can have one cloned. I would expect to spend around $300-$700 for this option.

Option 3 is to just drive and enjoy.

 

For my engine swap I used the donor's ECU and therefore had to change the VIN. I was able to "virginize" the ECU with my Autel IM608 scanner and learn the EIS's security codes. However the VIN did not change and caused problems. I therefore contacted Josh Chase at The Mercedes Shop for help. He easily changed the ECU's VIN for me.
I didn't know that the cluster also has security codes which have to match the EIS.
I suggest contacting Josh Chase and see if you have experience with this problem too. I'll believe Mike when he says the EEPROM has to be reprogrammed, but FYI that generally means de-soldering it and using a programming tool and then soldering it back in. Good Luck.
GREAT that you put in the effort, time and money to restore the car from the dead.

BTW - Search YouTube for "Ed Bolian SL500" as this YouTuber recently bought a very "bad" and barely running 2003 SL500 for $1500. Way worse condition than what you bought.