A VAG part number is not a random string. Nine digits and a trailing letter tell you which platform the part was designed for, which system it belongs to, and whether that letter means “newer version” or “different variant entirely”. Reading them properly is the difference between ordering the right module first time and paying return freight twice. Here is how the numbering actually works, with examples from parts that cross our bench every week.
The Three Blocks
Take 5Q0 907 273 as a pattern. The first block identifies the platform, or the first model the part was designed for. The second block is the function group — the system the part belongs to. The third block is the specific item inside that group. The trailing letter is the index, which can mean a revision, a variant, or both.
Function groups are consistent enough to be genuinely useful:
- 109 — timing belt and tensioner, as in 03L198119F and 06C109119C
- 121 — cooling and water pumps, as in 04E121600AA and 06L121111K
- 105 — flywheel and crank drive, as in 06J105266H
- 141 — clutch assemblies, as in 03L141025H
- 615 — brakes and hydraulics, as in 2Q0614517AN and 1K0614517EJ
- 905 / 907 — ignition and vehicle electrics: 07K905715F is an ignition coil, 3Q0907530AC is a gateway
- 920 — instrument cluster: 5G1920791B, 8W5920790E
- 941 / 945 — headlights and tail lights
- 853 / 807 — grilles and bumpers, while 827 covers tailgate and lid
- 953 — steering column electronics; 927 — transmission control
Once you know the groups, a photo of a label tells you what the part does before you have looked anything up. Anything ending in 920 is a cluster. Anything with 907 273 in the middle is a tyre pressure receiver. Anything in 121 sits in the cooling circuit. That single skill saves more mis-orders than any catalogue.
Prefix Families: Platform Tells
- 1K0 — PQ35 era: Golf 5, Golf 6, Jetta, early Passat. Examples include the 1K0614517EJ ESC hydraulic unit with MK60 controller and the 1K0953549CH multifunction steering wheel module.
- 2Q0 — MQB-A0: Polo 6, T-Cross, Ibiza, Arona, Kamiq, Scala, A1. The 2Q0614517AN ABS hydraulic unit is a textbook example.
- 5Q0 — the generic MQB electrical prefix, shared across Golf 7, Passat B8, Tiguan, Octavia III and Leon 5F. The 5Q0937084DH body control module and the 5Q0907273B TPMS control unit both live here.
- 5G0 / 5G1 / 5G6 — Golf 7 body, interior and screens specifically, including the 5G1920791B virtual cockpit.
- 5NA — Tiguan MK2 and Atlas/Teramont. The 5NA827566D rear view camera is Tiguan-only despite looking like a generic MQB part.
- 3Q0 — highline MQB electronics shared across the group, such as the 3Q0907530AC CAN gateway.
- 5WA — MQB Evo, meaning Golf 8, Octavia IV and Leon KL. The 5WA907530B gateway will not talk to a Golf 7 harness.
- 3G0 / 3GB — Passat B8 specific, as in the 3GB920790 digital cluster.
- 8W0 / 8W5 — Audi A4 B9 and A5. The 8W5920790E cluster and the 8W0907064CH BCM2 belong to that family.
- 4M0 / 4M1 — Audi Q7 4M and MLB Evo: the 4M1907468C data bus module and the 4M0907273B TPMS unit.
- 992 / 971 — Porsche model codes used as prefixes. 992 is the 911 generation, 971 is Panamera, which is why two visually identical TPMS receivers carry numbers from different families.
Eleven prefixes, one lesson: the first block is a compatibility hint, not a guarantee. 5Q0 and 5NA parts frequently interchange electrically and refuse to interchange physically.
Same Base Number, Different Index: Variant or Revision?
This is where most ordering mistakes happen. The 5Q0937084 BCM range runs across DH, DQ and EC. If you assume alphabetical progression — DH older, DQ newer, EC newest — you conclude that EC supersedes both. In practice these are different hardware and feature levels sharing one base number. Pin counts, LIN channels, LED drive capability and what they can switch all differ, and the index letter documents the variant rather than ranking it.
The same trap exists in the TPMS range, where 5Q0 907 273 and 5Q0 907 273B are different variants. What actually has to match is the frequency band the wheel sensors transmit on. A 433 MHz receiver will never see 315 MHz sensors, no matter how identical the label looks in a photograph.
Supersession: When the Number Changes and the Part Does Not
VAG supersedes upward: A is replaced by B, B by C. A parts system will show a “replaced by” chain, and the old index is no longer orderable. Two cautions. First, the new index can arrive with a different connector keyway or a firmware requirement, so the harness you built around the old part may not plug in. Second, a supersession can merge two previously distinct variants, which means the replacement needs coding the original did not.
Practical rule: if the car left the factory with index A and the catalogue now offers D, D will normally work and is normally the only thing you can buy. Check the software level the car expects before fitting, particularly on BCMs and gateways where you cannot simply flash your way out of a mismatch.
The Codes After the Index
Trim parts carry a colour code — 9B9 for black, with equivalents for beige and grey. It is not part of the part number and it gets dropped constantly in online listings, which is how a black door card arrives in grey. Mechanical assemblies sometimes carry a supplier code too; the 530 0480 10 on an INA timing kit is INA’s own reference, not a VAG number, and the two are not convertible by pattern.
Aftermarket manufacturers run entirely separate systems. A LUK dual clutch kit numbered 602 0006 00 or a SACHS flywheel numbered 2294 000 838 cannot be reverse-engineered into an OE number — you cross-reference through the manufacturer’s catalogue against the OE number the kit replaces.
Reading a Label From a Photo
Three things matter on a module sticker: the VAG number printed across the top, the software and hardware version lines beneath it, and any PR codes present. Cast-in numbers on an aluminium housing are mould or supplier references and mean nothing for ordering. If a seller photographs only the connector face, ask for the label — a number you cannot read is not a number you can verify.
A Three-Step Check Before You Buy
- Match the block and the index. Not just the first nine digits, and not just the familiar prefix.
- Match the physical and electrical variant. Frequency, connector keyway, pin count, colour code.
- Match the software and the car. Component protection, immobiliser, and whether the gateway in the car can even see the new address.
A number that matches all three is a part that fits. A number that matches only the first is how a cheap module becomes an expensive lesson. The BCM and gateway range is a good place to practise the reading, because those part numbers carry the most variant noise.
Does a higher index letter always mean a newer part?
No. On consumables and simple mechanical parts the letters usually walk upward as revisions. On electronics the index often denotes a variant with different hardware, and the 5Q0937084 family is the clearest example. Treat letters as identifiers and compare feature tables instead of assuming rank.
Can I fit a 5Q0 module into a 5NA car?
Sometimes. 5Q0 and 5NA share much of the MQB electrical architecture, but mounting, connector position and parameter sets differ. Check the connector and the software level before assuming interchangeability — and expect the bracket not to line up even when the plug does.
Why do some numbers have extra characters?
Colour codes on trim, supplier codes on some assemblies, and dimension suffixes on belts and hoses. The nine digits plus index is the part; everything after it is a variant qualifier you still have to match before you order.