VW TDI Custom ECU Chip Tune — Mk3/B4 AHU/1Z, 1996–1998 Jetta & Passat | KermaTDI

What it is
This is a custom-programmed ECU chip upgrade for early VW TDI models with a socketed engine computer — specifically the AHU and 1Z engine codes. Unlike a generic tune, each chip is individually written by KermaTDI's tuning department for your specific car's modifications and desired driving characteristics.

Fitment

• 1997–1998 VW Mk3 Jetta TDI, AHU engine
• 1996–1997 VW B4 Passat TDI, AHU or 1Z engine
• Also fits some 1999 Mk3 Jetta TDI with AHU engine — this is uncommon and mostly found in Canada. Call 877-537-6283 if you're unsure whether your car qualifies.

How the customization works
This isn't a one-size-fits-all chip. After ordering, KermaTDI follows up with a tuning questionnaire covering your car's modifications, your preferred driving characteristics, and your acceptable smoke level. The chip is then written specifically for that combination.

Installation
DIY install using common hand tools, following instructions provided with the chip. Installation requires physically opening the ECU to access the chip — KermaTDI provides a guide for ECU removal and chip swapping.

Important compatibility check — socketed vs. non-socketed ECU
Chip installation requires a socketed ECU. Some European-spec ECU versions are not socketed from the factory. If yours isn't socketed, you'll need to send your ECU to KermaTDI for socketing first, which carries a separate $150 fee. KermaTDI can help determine whether your ECU is already socketed if you're unsure.

Order requirements
Vehicle year/model and transmission type (manual or automatic) must be specified at checkout — the tune is written differently depending on transmission.

Common questions

Is this the same tune for every AHU/1Z car, or is it customized? Fully customized — each chip is written individually based on your car's specific modifications and your stated preferences for smoke level and driving feel.

Does my ECU need any prep work before the chip can be installed? Possibly — if your ECU isn't already socketed (common on some European-spec units), it needs to be sent to KermaTDI for socketing first, for an additional $150.

Can I install this myself? Yes, it's designed as a DIY install with common hand tools, and KermaTDI provides a guide for removing the ECU and swapping the chip.

Does this fit a 1999 Jetta? In limited cases — some 1999 Mk3 Jetta TDIs with the AHU engine code qualify, mostly Canadian-market cars. Call to confirm before ordering.

Does this work on an automatic transmission car? Transmission type must be specified at order time since the tune differs by transmission — confirm manual vs. automatic when ordering.