Audi A4 / S4 / RS4 standalone ECUs
Audi's mid-size range in the data, from 1.8T four-cylinder models to the 2.7-litre twin-turbo V6 in the B5 S4 and RS4.
- Chassis
- C4 · B5 · B6
- Years
- 1991–2006
- Engines
- 1.8T · 1.8T AWP · AEB/AJL 1.8T · APU 1.8T · BEX 1.8T · AAN 2.2 20V turbo
- Layout
- 4 or 5 or 6-cylinder, AWD
You have 21 plug-in ECU options for the Audi A4 / S4 / RS4 from Link, Haltech, MaxxECU and ECUMaster, 1 of them direct plug-in. The cheapest complete setup is ECUMaster at US$1,238 including the ECU. 55 wire-in ECUs can also run its 4 or 5 or 6-cylinder engine with a custom loom, from US$275.
Prices checked and include the ECU.
Your options for this car
New to this? Three ways to fit an aftermarket ECU explains each one in five minutes.
Dedicated plug-in 1
Built for this car. Goes where the factory ECU was and plugs straight into the factory loom.
From US$1,995 →
Standalone + adapter harness 20
A general-purpose ECU with an off-the-shelf harness that joins it to the factory ECU plug.
From US$1,238 →
Wire-in ECU 55
Any ECU with the right features, on a new or rewired loom. Best for race cars, swaps and big changes from factory.
From US$275 plus loom →
Reflash
Keep the factory ECU and rewrite its tune. Usually the cheapest, keeps every factory feature, but limited to what the factory hardware can control.
Reflash options for this car are still being checked.
Plug-in ECUs for the Audi A4 / S4 / RS4
21 options, cheapest first. Each one links to its full specs and sellers.
Audi A4 (AEB, AJL) MaxxECU STREET Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
Audi S2 / S4 / S6 (AAN, ADU, ABY) MaxxECU STREET Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
Audi S2 / S4 / S6 (AAN, ADU, ABY) MaxxECU RACE Plugin STANDARD
Kit: MaxxECU unit + plug-in adapter, no wideband sensor (STANDARD)
Audi A4 (AEB, AJL) MaxxECU RACE Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
Audi S2 / S4 / S6 (AAN, ADU, ABY) MaxxECU RACE Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
Audi S3/A4 1.8T (ME 7.5) MaxxECU RACE Plugin STANDARD
Kit: MaxxECU unit + plug-in adapter, no wideband sensor (STANDARD)
Audi S4/RS4 2.7 biturbo (ME 7.1) MaxxECU RACE Plugin STANDARD
Kit: MaxxECU unit + plug-in adapter, no wideband sensor (STANDARD)
Audi S3/A4 1.8T (ME 7.5) MaxxECU RACE Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
Audi S4/RS4 2.7 biturbo (ME 7.1) MaxxECU RACE Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
TTX Plug-In ECU (Audi TT / VW 1.8L Turbo, PQ34 Platform)
Likely compatible, unconfirmed by Link - check with tech support; Manual only; 121-pin two-connector header; 1.8T FWD or Haldex 4WD only; onboard MAP; built-in E-throttle
Audi S3/A4 1.8T (ME 7.5) MaxxECU RACE H20 Plugin EXTRA
Complete kit: MaxxECU unit + plug-in adapter + LSU 4.2 wideband + accessories (EXTRA)
Audi 1.8T (ME 7.5) MaxxECU RACE plugin adapter
Adapter harness only; MaxxECU unit sold separately
Audi S4 2.7 turbo (ME 7.1) MaxxECU RACE plugin adapter
Adapter harness only; MaxxECU unit sold separately
MaxxECU STREET/RACE Plugin adapter - Audi A4 1.8T REV2 (AEB, no E-Throttle)
Adapter harness only; MaxxECU unit sold separately
HT-212325 Nexus S2 Plug 'n' Play Adapter Harness Kit - VW/Audi 1.8T AWP
AWP engine only; manual; CAN dash developed on 2003 Beetle
HT-213325 Nexus S3 Plug 'n' Play Adapter Harness Kit - VW/Audi 1.8T AWP
AWP engine only; manual; CAN dash developed on 2003 Beetle
No plug-in is listed for that chassis and year. A wire-in ECU below will still fit with a custom loom.
Wire-in ECUs that can run this engine
Cheapest current unit from each brand with at least 6 injector and ignition outputs, so it runs fully sequential.
Add a loom: built by your tuner or a loom maker. Filter every wire-in ECU by features and price
Find a tuner for these ECUs
Shops with their own dyno that tune the brands above.
About the makers: Link · Haltech · MaxxECU · ECUMaster