05/04/2026
🔑 TRANSPONDER DEEP DIVE: NXP, TI, ST, Atmel & Mercedes Keys
(Save this — it’ll save you time, money, and headaches on the job)
The chip and the ID are NOT the same thing.
Think of it like this:
👉 The ID = the language the immobiliser speaks
👉 The chip = the hardware speaking that language
Get either one wrong… and the job fails — even if your tool says “programming successful.”
⚠️ Why this matters
Your tool reports the ID
Your supplier sells you the chip
If they don’t match exactly, you’re wasting time chasing faults that aren’t there.
🔍 Manufacturer Breakdown
🔹 NXP (Philips) – Most European vehicles
ID46 → PCF7936
ID47 → PCF794x (remote PCB integrated)
ID48 → Megamos Crypto
ID49 → NCF29A family
🔧 PCF794x Generations (This catches people out):
PCF7941 / 7946 → older generation (Hitag2, early remotes)
PCF7947 / 7948 → newer VAG/Renault applications
PCF7952 / 7953 → newer encrypted systems, often not backwards compatible
⚠️ They may share the same ID47, but the hardware is different
👉 Wrong generation = remote or immobiliser issues
⚠️ ID49 warning:
NCF29A comes in A / A1 / A3 revisions
They look identical when ordering
➡️ Use the wrong one on newer VAG MQB = no start, no explanation
✅ Best practice: default to A1 or A3
🔹 Texas Instruments (TI)
ID4C, ID4D, ID63
ID8A → DST AES (Toyota, Lexus, some Hyundai/Kia)
⚠️ Common mistake:
ID8A and ID49 show up on similar vehicles
👉 They are completely unrelated
🚫 NXP ≠ TI — don’t mix them up
🔹 Atmel (ATA5577)
Found in super chips / universal keys
✅ Great for older protocols
🚫 Does NOT cover: ID48, ID49, ID8A, Mercedes
👉 Know its limits before relying on it
🔹 STMicroelectronics
Found in modules, not keys
HC05 / HC08 (Mercedes EIS)
👉 MCU type determines your programming method
🔹 Mercedes Keys (Know the difference!)
This isn’t one system — it’s FOUR:
Motorola EIS
NEC (IR, password-based)
BGA / FBS3
FBS4 → Dealer only
⚠️ FBS3 & FBS4 overlap in year and key style
👉 Always verify via VIN + SA code (803/804)
🧠 Final Tip
Start with:
✔️ Make
✔️ Model
✔️ Year
✔️ ID type
Then go deeper into the chip when things don’t add up — that’s what gets the job over the line.
💬 Been caught out by PCF794x generations or NCF29A revisions? Or the FBS3/FBS4 overlap?
Drop your experience below 👇
📊 Full reference data + AKL procedures:
👉 www.autoimmoiq.com
