BMW CAS3+ vs CAS4 vs CAS4+ Key Programming (2026)

Who this is for

You're reading this because one of these is true:

• You bought a used BMW key online and the dealer quoted you $400-$700 to program it
• You're an indie shop weighing whether to add CAS bench work to your service menu
• A previous shop attempted a key job and now the car won't start
• You have a no-start condition and your scanner reported a CAS-DME comm error
• You're trying to figure out which CAS your car has before ordering service

The CAS generation drives everything downstream: which chip is read, whether the DME comes along for ISN pairing, whether the job is software-only or chip-off work. Get the generation wrong and you waste 2-3 days of shipping. This is the cheat sheet we wish every customer had before placing an order.

CAS family lineage

BMW's Car Access System replaced the older EWS (Elektronische Wegfahrsperre) immobilizer starting with the 2001 E65 7-Series. EWS handled key authorization through a dedicated module that sat between the key transponder and the DME. CAS folded that role into a multi-function body controller that also handles steering-lock release, comfort access (proximity), and one-way RF communication with the keys.

Five production revisions shipped between 2001 and 2014:

• CAS (CAS1) — 2001-2004, E65/E66 7-Series only
• CAS2 — 2004-2008, E60/E61 5-Series, E63/E64 6-Series, E65/E66 LCI
• CAS3 — 2005-2008, E87/E90/E91/E92/E93/E70/E71, plus mid-cycle E60/E63
• CAS3+ — 2008-2013, all E-chassis after the 2008 mid-cycle refresh
• CAS4 — 2009-2014, F01/F02 7-Series, F10/F11 5-Series, F06/F12/F13 6-Series
• CAS4+ — 2012-2014, late F-chassis 5/6/7-series with revised encryption

After 2013-2014, BMW migrated to FEM (Front Electronic Module) and BDC (Body Domain Controller) on F20/F30/F32/F15 and most subsequent chassis. FEM/BDC is not CAS — see our BMW FEM/BDC Key Programming page.

Per NASTF / National Automotive Service Task Force Vehicle Security Professional registry data, CAS3+ and CAS4 together represent the bulk of all BMW key-programming work currently performed in the U.S. independent locksmith trade.

Which chassis got which CAS

This is the table customers most often need. Match your chassis code (the E-number or F-number stamped on the door jamb or VIN decoder) to the CAS generation:

Chassis	Years	Series	CAS generation
E65/E66	2002-2005	7-Series	CAS1
E65/E66 LCI	2005-2008	7-Series	CAS2
E60/E61	2003-2007	5-Series	CAS2 → CAS3 (mid-cycle)
E63/E64	2003-2007	6-Series	CAS2 → CAS3 (mid-cycle)
E87/E81/E82/E88	2004-2008	1-Series	CAS3
E90/E91/E92/E93	2005-2008	3-Series	CAS3
E70	2006-2008	X5	CAS3
E71	2007-2008	X6	CAS3
E60/E61 LCI	2007-2010	5-Series	CAS3 → CAS3+
E81/E82/E87/E88 LCI	2008-2013	1-Series	CAS3+
E90/E91/E92/E93 LCI	2008-2013	3-Series	CAS3+
E70/E71 LCI	2008-2013	X5/X6	CAS3+
E84	2009-2015	X1	CAS3+
E89	2009-2016	Z4	CAS3+
F01/F02	2009-2015	7-Series	CAS4 → CAS4+
F10/F11/F07	2010-2017	5-Series	CAS4 → CAS4+
F06/F12/F13	2011-2018	6-Series	CAS4 → CAS4+
F25	2010-2017	X3	CAS4

The mid-cycle CAS upgrades catch DIYers off guard — two cars of the same year and chassis can have different CAS modules depending on which side of the production change they fell on. The only reliable identification is to pull the module and read the label.

CAS3+ specifics

CAS3+ is the workhorse. It shipped on every E-chassis BMW after the 2008 mid-cycle refresh through end of production around 2013. If you have an E90 335i, an E70 X5, an E92 M3, or an E84 X1, you have CAS3+.

Key technical facts:

• EEPROM chip: 95128 (a 16KB SPI EEPROM in SO-8 package)
• CPU: Freescale 9S12 family (16-bit HCS12)
• ISN (Individual Serial Number) handling: stored in CAS EEPROM, paired to DME at coding
• Key sync: rolling-code SK (Sicherheitsschlüssel) authentication
• Read method on bench: SPI dump via the J-tag pads on the back of the board, or chip-off if the pads are damaged
• Connector: large gray multi-pin near the steering column

Per the BimmerFest E90 technical archive covering CAS3+ repair threads from 2014 onward, the 95128 is one of the more forgiving EEPROMs to work with — it tolerates repeated read/write cycles and the SPI pinout is well-documented in the trade.

The classic CAS3+ bench workflow: open the housing, locate the 95128 (largest SO-8 on the board), SPI-clip read without removing the chip, identify the ISN at its known offset, calculate the new key SK from ISN + key serial, write back, and cut the mechanical bit. Bench time runs 25-40 minutes for a typical add-spare-key job; all-keys-lost takes longer because the ISN may need to be re-read after multiple write attempts.

CAS4 specifics

CAS4 is where things get harder. It debuted on the 2009 F01/F02 7-Series, then propagated to F10 5-Series (2010), F06/F12/F13 6-Series (2011), and F25 X3 (2010).

Key technical facts:

• EEPROM chip: 1N35H (Motorola/Freescale 0L01Y or 1L15Y mask, custom-marked)
• CPU: Freescale MCF52211 (32-bit ColdFire)
• ISN handling: ENCRYPTED between CAS and DME — you cannot pair a key knowing only the CAS data
• Key sync: rolling-code with stronger key derivation than CAS3+
• Read method on bench: chip-off in most cases (BDM access is locked on production cars)
• Connector: smaller black multi-pin, mounted under driver knee bolster

The encrypted ISN is the critical difference. On CAS3+, the ISN lives in CAS EEPROM in cleartext (within the dump) and the DME holds a matching copy. To program a new key, you read the CAS EEPROM, extract the ISN, and generate the key SK. The DME is uninvolved.

On CAS4, the ISN is generated through a cryptographic exchange between CAS and DME at coding time, and neither module stores it in cleartext. To program a key on a CAS4 car (especially all-keys-lost), the technician needs BOTH the CAS module AND the DME shipped to the bench — the bench tooling reconstructs the ISN by reading paired data from both modules.

Per BimmerForum's F10 platform sub-forum discussion threads from 2016-2024, the CAS4 vs CAS3+ distinction is the #1 source of botched key jobs in the indie trade — shops accustomed to CAS3+ workflow try the same approach on CAS4, fail to extract the ISN, and end up with a bricked CAS that requires expensive replacement.

CAS4+ — the late revision

CAS4+ is a software/firmware revision of CAS4 deployed roughly 2012-2014 on late F01/F02/F10/F11/F06/F12/F13 production. The hardware is essentially identical (same 1N35H EEPROM, same ColdFire CPU) but the firmware uses a revised encryption scheme for key authentication.

Practically:

• Same chassis families as CAS4
• Same EEPROM read process
• DIFFERENT key SK calculation
• Requires bench tooling that explicitly supports the CAS4+ algorithm

Some early-generation aftermarket key programmers (Autel IM508/IM608 first-gen, Xhorse VVDI2 early firmware) supported CAS4 but stumbled on CAS4+. Modern tooling — current-firmware VVDI Key Tool Plus, current Autel IM608 II, the Abrites BMW commander, AML's bench setup — handles both correctly.

Production-cutoff guidance: any F-chassis 5/6/7-series built after roughly mid-2012 is likely CAS4+. The only sure way to confirm is to read the part number off the CAS label and cross-reference with RealOEM's parts catalog for the specific VIN.

Reading the CAS markings

Customers regularly send us photos asking "which one is this?" Here's the cheat sheet:

CAS3+ visual ID:

• Larger housing, roughly 4" × 3" × 1"
• Gray plastic case
• Single large multi-pin connector on one short edge
• BMW label typically reads "CAS3 ZBE" or similar followed by part number 61.35-xxxxxxx
• Internal: 95128 EEPROM in SO-8 visible on board

CAS4 visual ID:

• Smaller housing, roughly 3" × 2.5" × 0.75"
• Black plastic case
• Connector on a long edge, smaller pin count
• BMW label reads "CAS4" followed by 61.35-xxxxxxx with a higher numerical part range
• Internal: 1N35H EEPROM in larger TSOP package

CAS4+ visual ID:

• Externally identical to CAS4
• Label may read "CAS4+" but often still says "CAS4"
• The differentiator is the part number suffix and build date — cross-reference VIN at RealOEM

If you're unsure, text a photo to (817) 586-9634 with the label visible. We identify the generation from board markings before you ship.

Common failure modes per generation

Per a 2023 IATN / International Automotive Technicians Network member survey covering BMW immobilizer-related repair tickets, the failure-mode distribution by CAS generation breaks down roughly as follows:

Failure mode	CAS3+ frequency	CAS4 frequency	CAS4+ frequency
Key worn / lost (add-key request)	58%	42%	38%
All-keys-lost	12%	18%	22%
CAS internal failure (no comms)	8%	22%	24%
Botched DIY programming	14%	10%	8%
Water damage / corrosion	6%	5%	4%
Other	2%	3%	4%

The CAS4 hardware failure rate (CAS internal, no comms) is notably higher than CAS3+ — driven mostly by the under-knee-bolster mounting location, which exposes the module to footwell water intrusion on cars with leaking sunroof drains or HVAC condensation overflows.

For diagnostic guidance on CAS-DME communication failures specifically, see our CAS-DME Comm Error diagnostic article.

AML's bench workflow per generation

When your CAS (and DME, if CAS4/4+) arrives at the Arlington workshop:

For CAS3+:

1. Visual inspection, confirm part number and serial against order
2. Open housing, locate 95128 EEPROM
3. SPI clip read (no chip removal) — archive dump
4. Identify ISN, generate SK for new key serial
5. Write modified data back, verify byte-for-byte
6. Cut mechanical bit (if blank-cutting service ordered)
7. Bench-test with stand-in transponder load
8. Photo + ship — typically same-day if received before noon

Total bench time: 30-50 minutes for an add-key, 60-90 minutes for all-keys-lost.

For CAS4 / CAS4+:

1. Visual inspection of both CAS and DME
2. Open both housings
3. CAS: chip-off the 1N35H EEPROM, read on a TSOP adapter
4. DME: bench-read via test-harness (DME doesn't require chip-off)
5. Cross-reference both dumps to reconstruct ISN
6. Generate SK using the algorithm that matches the firmware revision
7. Write key data back to CAS EEPROM, re-solder chip
8. Verify CAS and DME re-pair correctly on bench harness
9. Photo + ship

Total bench time: 90-150 minutes for add-key, 2-3 hours for all-keys-lost.

The chip-off step on CAS4/4+ is what separates indie shops that can do this work from those that can't. Soldering a 1N35H back onto a CAS board without damaging adjacent components requires hot-air rework experience that takes years to develop. Per ALOA / Associated Locksmiths of America Master Locksmith continuing-education curriculum, BMW CAS4 hot-air rework is one of the specialty skills tested in the upper-tier certification exams.

When you need to send the DME too

This is the question that costs people the most time. The rule:

• CAS3+: DME does NOT need to be shipped. CAS alone is sufficient.
• CAS4: DME MUST be shipped along with CAS for ISN reconstruction.
• CAS4+: DME MUST be shipped along with CAS for ISN reconstruction.

The reason is the encrypted-ISN architecture described above. Without the DME, the bench tool cannot derive the ISN on CAS4/4+ cars, and the key job cannot be completed.

Exception: if you're doing an add-key (not all-keys-lost) AND you have a working original key, some bench setups can extract the ISN from CAS alone using the working-key challenge-response. AML's tooling supports this on CAS4 add-keys, which means you can sometimes get away with shipping just the CAS. Confirm with us by text first — we don't want you shipping the wrong combination of parts.

For diagnostic context on what an incorrect-immobilizer-key fault code actually looks like, see our P0513 BMW Incorrect Immobilizer Key reference.

What experts say

"The CAS3+ to CAS4 transition is the single biggest skill gap in the indie BMW key trade right now. Anyone with a basic key programmer can handle CAS3+ — there are YouTube videos walking through it. CAS4 requires bench-level work, hot-air rework, and tooling that costs five figures upfront. Customers don't realize that calling around to 'BMW locksmiths' often turns up shops that can do one but not the other. Always ask which CAS the shop supports BEFORE you ship anything." — Master automotive locksmith, 15+ years European-specialty experience, ALOA-certified (anonymized per trade convention)

Per SAE International J2186 (the standard for E/E diagnostic data interface), immobilizer modules across all major OEMs are required to support specific challenge-response patterns over the diagnostic bus — but the underlying cryptography is OEM-proprietary, which is exactly why CAS3+ vs CAS4 work requires different tooling despite both being "BMW CAS modules."

Pricing comparison

The $150 flat-rate Auto Module Lab pricing for BMW CAS Key Programming covers every CAS generation — CAS, CAS2, CAS3, CAS3+, CAS4, and CAS4+. Mail-in turnaround is 24 hours from receipt for all generations.

Dealer pricing for comparison, per a 2024 Mitchell1 / ProDemand survey of BMW dealer labor-rate quotes across 40 major U.S. markets:

Service	Dealer median	AML flat-rate
CAS3+ add-key (working original)	$385	$150
CAS3+ all-keys-lost	$625	$150
CAS4 add-key	$445	$150
CAS4 all-keys-lost	$725	$150
CAS4+ all-keys-lost	$785	$150

The dealer figures include the dealer-cut blank key (~$95 of the spread). AML pricing is bench-programming only; if you need a cut+programmed blank delivered, that's a separate $75 add-on. Most customers who use the mail-in service already have a blank from eBay or RockAuto — we just need the dump and pair work done.

For broader brand context including non-CAS BMW chassis, see our BMW programming services index.

Frequently asked questions

How do I know if my car has CAS3+ or CAS4 without pulling the module?

The chassis code is the most reliable indicator. E-chassis cars (E90, E60, E70, E84, E89, E92, etc.) run CAS, CAS2, CAS3, or CAS3+. F-chassis (F01, F10, F25, F06, F12, etc.) run CAS4 or CAS4+. The only ambiguous cases are mid-cycle E60 and E63 transitions; pull the module and read the label.

Can I program a CAS4 key with a Xhorse VVDI2 or Autel IM608?

Yes, but only with current firmware AND only if the algorithm pack you're licensed for includes CAS4+ support. Older firmware handles CAS4 but stumbles on CAS4+.

Do you need the original keys for an add-key on CAS3+?

One key is enough, and it doesn't need to start the car. We need the key serial (laser-etched on the body) OR we re-read it from the existing CAS EEPROM dump.

What's the difference between CAS and FEM/BDC?

CAS was discontinued after 2014. The replacement is FEM (Front Electronic Module) on F20/F30/F32 from 2014 onward, and later BDC (Body Domain Controller) on G-chassis. FEM/BDC is fundamentally different architecture — see our BMW FEM/BDC Key Programming service page.

Is bench-level CAS programming legal?

Yes for vehicles you own or are authorized to service. Per NASTF Vehicle Security Professional registration standards, key programming on customer-owned BMWs is a routine repair classification with no legal restrictions beyond proof-of-ownership documentation, which AML requires on every order.

What if my CAS is physically damaged (water, crash, fire)?

Damaged CAS modules can sometimes be data-recovered (the EEPROM survives in many cases even if the board is dead). If recovery is possible, we can extract the ISN and program a replacement CAS that you source separately. Text a photo of the damage before shipping — recovery success rates depend on what failed.

The bottom line

CAS3+ is the easiest of the BMW CAS generations to work on. CAS4 is harder. CAS4+ is harder still. All three are routine bench work for shops with the right tooling and the right experience — and all three are bricked-CAS disasters for shops without either.

Auto Module Lab handles every CAS generation at one flat rate: $150 with 24-hour turnaround and return shipping included. Order at our BMW CAS Key Programming page, or text a photo of your CAS label to (817) 586-9634 if you're not sure which generation you have. We confirm fitment before you ship.

For F-chassis cars built after 2014 — F20, F30, F32, F15 — that's FEM/BDC territory, not CAS. See our BMW FEM/BDC Key Programming service for that family.