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Mercedes immobilisers FBS3 vs FBS4 Explained

FBS3 vs FBS4. The Mercedes immobiliser divide.

Mercedes split its immobiliser line in half around 2016 with a system change called FBS4. The change has nothing to do with how the car drives — but everything to do with whether an independent locksmith can work on it. Here's the honest explainer.

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At a glance

The two options,
side by side.

Option A

FBS3 (roughly 2009-2015)

The third-generation Mercedes immobiliser. Independent locksmiths can fully programme keys, do all-keys-lost, adapt EIS modules. Full ecosystem of aftermarket support.

Option B

FBS4 (2016 onwards)

The fourth-generation system. Uses encrypted online authentication with Mercedes servers. Independent locksmiths cannot programme — only the dealer can.

2 opts
Compared in depth
9
Detailed comparisons
20+ yrs
Industry experience
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Google rated
Detailed comparison

Feature by feature,
how they compare.

Feature
FBS3 (roughly 2009-2015)
FBS4 (2016 onwards)
When introduced
2009 (rolled out gradually).
2016 (rolled out gradually 2015-2017).
Models on FBS3
C-Class W204, E-Class W212/W207, ML/GLE W166, A-Class W176, B-Class W246, S-Class W221, Sprinter W906, and equivalents.
C-Class W205, E-Class W213, GLC, GLE W167, S-Class W222, A-Class W177, Sprinter VS30, current SL/AMG GT and similar.
Authentication method
Local cryptographic authentication via EIS module. Keys read/written by independent tools.
Online dealer-server cryptographic authentication. Server-side validation required for any new key.
Independent can programme spare keys?
Yes.
No.
Independent can do all-keys-lost?
Yes.
No.
Dealer required for key work?
No — independent is fine.
Yes — dealer is the only option.
Typical key cost
Lower (independent or dealer).
Higher (dealer only, plus recovery).
Typical lead time
Same-day to next-day at independent.
1-3 weeks at dealer.
Best for
Most Mercedes from 2009-2015. We handle these every week.
Mercedes 2016+. We honestly tell you it's outside scope.
When option A wins

When FBS3 (roughly 2009-2015)
is the right choice.

FBS3 (roughly 2009-2015) comes out ahead in these scenarios — straight talk about when this is the answer.

Your Mercedes is 2009-2015

FBS3 systems are fully serviceable by independents. We handle every model — saloons, SUVs, Sprinters, AMGs — for spare keys, all-keys-lost, and EIS module work.

You need quick turnaround

FBS3 work is typically same-day at an independent. The dealer might offer the same on a 2016+ FBS4 car but at a much higher cost and longer lead time.

Cost matters

FBS3 work at an independent is dramatically less than equivalent dealer pricing. The cost gap on FBS4 (where the dealer is the only option) is unavoidable.

You want flexibility on fobs

FBS3 supports OEM and aftermarket fobs. FBS4 dealers fit OEM only.

When option B wins

When FBS4 (2016 onwards)
is the right choice.

FBS4 (2016 onwards) comes out ahead in these scenarios — honest about where it has the edge.

Your Mercedes is 2016+

FBS4 requires dealer-server access we don't have. The dealer is your only option for these. We're honest about this from the start, not after taking a booking.

You're uncertain on year

Transition models (2015-2016) can be FBS3 or FBS4 depending on production date and model. We confirm from your registration before booking.

You want manufacturer warranty on the key

Dealer-fitted FBS4 keys come with manufacturer warranty chain. Independents on FBS3 offer their own warranty — strong but different in structure.

The FBS3/FBS4 divide is a hard line in Mercedes key work. If you have a 2009-2015 Mercedes, we handle the job efficiently and cost-effectively. If you have a 2016+ Mercedes, we tell you straight up that the dealer is the only option — no wasted travel, no false promises. WhatsApp us your registration if you're uncertain, and we'll confirm in minutes.

Get a quote
Honest advice,
fixed quote.

Not sure which option fits your situation? Send your registration and a brief description — we'll tell you straight whether independent or dealer is the right fit for your specific job. No upselling, no padding.

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FAQ

Common questions.

How do I know if my Mercedes is FBS3 or FBS4?
Rough rule: 2009-2015 = FBS3, 2016+ = FBS4. But there's a transition zone (2015-2016) where it depends on production date and model. Send your registration to us and we'll confirm exactly within minutes.
Why did Mercedes change the system?
Mercedes redesigned around 2014-2015 with two goals: stronger security against vehicle theft (the encrypted server authentication is harder to bypass), and tighter dealer control over key work (commercial benefit to the dealer network).
Can any independent crack FBS4?
No. Despite occasional online claims, no current UK independent can programme FBS4 keys without dealer-server access. Any "FBS4 specialist" claiming otherwise is either misrepresenting their service or doing something dodgy.
Will FBS4 eventually become serviceable by independents?
Possibly. FBS3 itself was server-protected initially before tools caught up. Whether the same happens with FBS4 depends on continued tooling development by aftermarket manufacturers. No timeframe to commit to today.
Is FBS4 actually more secure?
For its design purpose, yes — significantly harder to bypass via classical attack vectors. Whether it has reduced theft of Mercedes models is debated; thieves moved to relay-amplification attacks instead, which both FBS3 and FBS4 are vulnerable to.
What if my FBS4 Mercedes needs a spare key urgently?
Honest answer: the dealer is your only option, and dealer lead times are typically 1-3 weeks for an appointment plus the time for parts. Plan ahead if you can — don't wait until you only have one key.
Get in touch

Free quote.

Send your registration and we'll confirm exactly what's involved — fixed price, no surprises. Most quotes back within minutes, 7 days a week.

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