[It Worked!] MercedesBenz SL400 won’t crank after battery died - code needed?

3271 views - Last reply: February 20, 2025
This topic is closed for new replies.
Ultrasonic
Member since June 2022 • 136 posts

Where's the key code hidden on a MercedesBenz SL400 for key programming?

Posted on February 20, 2025
Adminbot
Staff Member • 1224 posts

Hello! We've developed a VIN-based tool to help you get your key code for the MercedesBenz SL400. Check it out here: VIN Key Code Generator.

Posted on February 21, 2025

Replies (3)

Xfactor
Member • 29 posts

Still can’t find the code for my MercedesBenz SL400. This might do it.

February 21, 2025 Reply
Happycamper
Member • 97 posts

Following closely—this could be the fix I need for my MercedesBenz SL400.

February 22, 2025 Reply
Gizmoguy
Member • 81 posts

Great info! Needed this for my old MercedesBenz SL400.

February 23, 2025 Reply

Check the news !

Annual Muscle Car Meetup
🏎️ Local Meetup: Annual Muscle Car Meetup
The event local car fans have been waiting for

🗺️ Where: Community College Campus
⏰ When: May 25 @ 11AM-6PM

Event features:
Photoshoot Area | Ride-Alongs

🔩 Forum Members: Forum staff will be there - come say hi! 👍

🧰 Off-Road Vehicle Build Day

👨‍🏫 Instructors:
• 4x4 Builder Mark Jensen
• Race Engineer Emily Torres

🔌 Hands-On Activities:
• Complete brake system overhaul demo
• 4-hour intensive training
• Personal coaching

📅 Skills Covered:
Torque specs | Bleeding procedures | Pad selection

🚙 May 17, 2026 at 9:00 AM (4-hour)

✨ Bring your own project - we'll help you work on it!

Workshop: Off-Road Vehicle Build Day
Street to Strip Tuning Workshop

🔋 Street to Strip Tuning Workshop

🧰 Instructor: Factory ECU Engineer Dr. Sophia Chen

📱 Workshop Includes:
• Live dyno tuning demonstrations
• 4-hour intensive hands-on training
• NVH reduction | Drivability tuning | Daily driver balance

📉 Bonus: Certificate of completion

🔌 Next Session: May 11, 2026 at 4:00 PM

Customize Your Tuning Focus:

🚀 Performance Mod Cost Estimator

Warning: Cheap parts often cost more in the long run due to failures

Vehicle Information

Modification Information

Additional Options

🔑 Car Key & Fob FAQ

Common questions about key programming, fob issues, and replacement options

Key Programming
Common reasons: wrong key type for your vehicle, anti-theft system needs reset, low car battery voltage during programming, or the key isn't properly synced. Some cars also have programming limits (only 2-4 keys can be registered).
Key Tip: Consider key insurance for expensive smart keys
Cost & Options
Locksmiths are typically 30-50% cheaper than dealerships for key replacement and programming. However, some newer models (especially luxury brands) may require dealer-only programming tools. Always get quotes from both.
Key Programming
Common reasons: wrong key type for your vehicle, anti-theft system needs reset, low car battery voltage during programming, or the key isn't properly synced. Some cars also have programming limits (only 2-4 keys can be registered).
Key Fob Issues
Many cars have a resync procedure: 1) Press lock/unlock buttons while near the car 2) Insert key and turn ignition on/off in a specific pattern 3) Use a sequence of button presses. Check your manual for exact steps - procedures vary widely by manufacturer.
Key Fob Issues
1) Find the seam and pry open the fob (some have tiny screws) 2) Note battery orientation 3) Remove old battery (CR2032 is most common) 4) Insert new battery 5) Reassemble. Test all buttons - if issues remain, the fob may need reprogramming.
Key Tip: Keep spare keys in a faraday bag to prevent signal amplification theft
Key Fact: Key fob batteries typically last 3-4 years with normal use

🔑 KEY SERVICES CLASSIFIEDS

Mobile Key Programming Service
$75+
Posted: Apr 30, 2026
Professional car key programming for most makes/models. We come to you! Transponder keys, fobs, and smart keys. Same-day service available. All work guaranteed.
Call: 299-579-1240
Lost Car Key Replacement
$120+
Posted: Apr 26, 2026
Lost all your keys? We can cut and program new ones even without originals. Dealership alternative at 40% less. Proof of ownership required. Serving all major brands.
Call: 405-524-2707
Car Key Extraction Service
$45+
Posted: Apr 21, 2026
Broken key stuck in ignition or door? We can remove it without damage and make new keys same day. Emergency service available 24/7 for lockouts.
Call: 305-622-4278
Anti-Theft System Repair
$85+
Posted: Apr 24, 2026
Fixing security light issues, PATS systems, and ignition immobilizers. Proper diagnosis before repair. Most vehicles serviced same day. Warranty on all work.
Call: 284-303-3604
Ads refreshed daily • Licensed professionals • Mobile services available

🔑 Upcoming Key & Immobilizer Services

Seminar
May 16, 2026

Immobilizer System Seminar

by The Key Lab
Learn how to extract key codes from VIN numbers and decode vehicle security information
Seminar
May 25, 2026

Immobilizer System Seminar

by The Key Lab
Become certified in vehicle security systems with our intensive 2-day course
Seminar
May 12, 2026

Car Security Certification Course

by Immobilizer Experts
Live demonstration of the latest anti-theft technologies and bypass prevention methods
Seminar
May 5, 2026

Smart Key Programming Class

by Mobile Key Tech
Become certified in vehicle security systems with our intensive 2-day course

Need immediate service? Call our 24/7 hotline: 1-800-KEY-HELP

Want to list your key service? Join our provider network

Last posts on the forum