ALH into A4 Avant Quattro B5 Questions


Active member
Aug 27, 2023
North Carolina
2002 Jetta TDI 2003 Jetta TDI
I'm pretty headstrong on the idea of swapping an ALH into a B5, I like the look of the car and having an awd diesel wagon sounds like a dream. I'm US unfortunately and I don't believe the ALH was ever in an awd format here, and I imagine importing something similar from EU would be costly. So I'm coming here just trying to start a scratch pad/parts list and ask for some advice with this. I've done many engine jobs but never involved myself with any swaps where one goes in that didn't come out so I'm green for sure. I have two options for bodies, one being a 99 with a 1.8T 5speed and the other being an 01 1.8T with an auto. Both have engine issues and are a cheap solid shells. I'm leaning towards the manual as I would like to avoid messing around under the dash installing a clutch pedal or fooling around with the wiring under there. From a previous forum post I gathered that a 02X Transmission from a newer 2.0 would be best suited for a diesel but I haven't found any on marketplace except for an 01E from an S4, which I was curious about as it seemed to have similar ratios and was really cheap. I believe I can use the driveshaft from an auto driveline and the cv's from the 02x. Engine wise I already have an ALH laying around. Longitudinally mounting it doesn't seem too difficult, I could take inspiration from some ranger swaps but I would like to retain a/c and modify the cooling and intercooler system from the 1.8t for alh if possible. The main thing that's stumping me is harness/ecu/wiring. I'm assuming I need an ALH harness and the know how to wire that in to the factory harness somewhere somehow. Let's say I figure that out, do I modify the audi ECU for a diesel application? is that even possible? or would I have to adapt an ALH ecu by changing pinouts and connectors and such? I've heard talk about EDC15, immobilizers, can bus, and I don't have a clue about any of this stuff so some resources on that would be great.


Veteran Member
Jan 6, 2019
96 B4V
It's a deep rabbit hole on the swap and engine management details, but you'll have to just dive in and do a lot of reading. Hard to sum it all up (even if I knew enough to do that) in one place since so much of it depends on your application and what you want to do. But it's all been done. Some of the info you'll find out there in old build threads, and other stuff you'll have the enjoyment and satisfaction of figuring out for yourself. :)

The mounting and physical installation will be straightforward provided you use mounting parts from a late 1.8T. Both the 99 and 01 should have those, though I think the 99 might be a crossover year so confirm that. You want the version of the 1.8T that uses an internal water pump driven by the timing belt to give you the most usable mounting parts for installing an ALH or similar. If you start with a chassis that has the early block 1.8T with external water pump that's fine but you'll need to source mounting parts from a later style 1.8T (or BHW TDI Passat B5.5 -- OR swap in an AHU or 1Z instead of the ALH, since those TDIs use the early style mounting system too). Avoid an A4 earlier than 1999 though, since you want drive-by-wire throttle, not cable throttle. DBW saves you another step in the electrical part of the conversion.

As for electronic controls, there are many paths. You can restructure the stock ALH harness to work in the B5 chassis but it will involve significant work to make routing clean, and lots of connector re-pinning, hacking up the gasser 1.8T harness for pieces, etc. Higher cost upfront but much easier in the long run IMHO would be to start with a correct B5 TDI harness from Europe (avoid ones from England since RHD configurations are different under the hood). It is true that the ALH never came in a longitudinal car, but other VE rotary pump type TDIs (1Z, AHU, AHH, AFN) did come in B5 Passats and Audis elsewhere. You can adapt a harness and ECM from one of those engines to run an ALH relatively easily, and if you get a compatible harness then many parts of it will just plug right into the B5 plenum box and wire loom routings will be easy and clean without you having to do much work. All depends on your budget, skills, and time but anything is achievable by whatever route. Like anything else you can pay more and work less or pay less and work more.

Fuel, cooling, A/C systems will also need thought but I'll stop here. :)


TDIClub Enthusiast, Macht Schnell! Vendor , w/Busi
Oct 18, 2010
3 Spruce st Wareham, gateway to Cape Cod Massachus
'91 GTI CJAA swap,'02 Jetta wagon ALH swap, '03 GTI 1.8T rally car, '03 Sprinter 3500
KMH motors aka Keith Harley has done a couple longitudinal ALH swaps, including a B5 quattro. I'm sure he could answer some of your questions.