VW / Audi / Seat / Skoda (VAG) Bosch EDC15VM+ Engine ECU Repairs

Type: Bosch
Fits: VAG – Audi / Seat / Skoda / Volkswagen (VW)
Fuel: Diesel
Ref: ECUT332225

Note: This ECU may also fit other models.

Take the panel off at the foot of the windscreen on one of these cars and the engine ECU is right there, under the wipers, sitting in a lidded box in the tray. It is not in the cabin behind the glovebox, and it is not bolted to the engine, which are the two places people look first. Diesel engine ECUs are what we test and rebuild here, and this is one of them.

That tray is a drain, and drains block. Everything that comes off the bonnet ends up in it — leaves through the autumn, moss off the screen surround, pine needles if the car lives under a tree — and all of it is supposed to leave through two small holes. Once those holes silt up the tray stops draining and starts holding, and the box with the ECU in it is sitting in whatever the tray is holding.

The box is meant to keep that out, and for a long time it does. What lets it down is the seal around the lid, which hardens with age and stops sitting flat, and the fact that the lid may have been off before — for a wiper linkage, a pollen filter, some earlier job under the same panel — and has not gone back down as tightly as it came off. After that, what gets in is not spray off the road. It is standing water.

From the driver’s seat it does not look like a clean breakdown. It looks like weather. The car is fine for weeks, then refuses to start the morning after heavy rain or a wash, and starts perfectly again once everything under the panel has dried out. Or it goes the other way and the unit stops answering altogether, so the garage plugs in and cannot get a word out of it. When a fault keeps time with the weather like that, where the ECU sits is worth knowing before anything else is taken off the car.

It also changes what needs doing, because there are two jobs here and not one. The first is the unit itself. An intermittent that only shows up in the wet is hard to pin down while the ECU is still in the car, because on a dry day it behaves; off the car and under test, what is wrong with it stops depending on the weather. Testing is what establishes the damage; the symptom on its own only points at it.

The second job is on the car, and nobody can do it for you at a distance. Clear the scuttle drains until water poured into the tray runs straight back out, and check the lid and its seal before anything goes back under there. Leave that half undone and whatever is fitted next is standing in the same water as the unit it replaced.

Contamination that has been sitting in a unit for a long time is not always recoverable, and testing is what settles that either way. Cloning and immobiliser bypass are not work we take on, and neither is remapping.

This one page is broader than a single engine. The numbers below take in the 1.9 TDI cars — Golf IV and Bora, the Leon, the Octavia, the A4 — on engines including ALH and AHU, the 2.5 TDI V6 in the A6 and the B6 A4 and in the Passat on AKN, and the T4 Transporter and Caravelle van. Three quite different engines, which is why it runs as long as it does.

The EDC15V is a separate unit and has an entry of its own.

If the car is an Audi and what came out from under the panel is a different Bosch unit altogether, the rest of the Audi range we repair is grouped in one place.

The route through the workshop does not change from one unit to the next. It is registered against its own job, gone over by eye for physical damage, then put on electrical test before anyone offers an opinion on it. You hear the result first — what the test showed and what the repair involves — and no chargeable work begins until you have agreed to it. The repair is carried out here in our own UK workshop, by the engineers who tested the unit, on the board that came off your car rather than by swapping the unit for another. After the repair it goes back on test, and only a pass releases it. That repair is warranted for 24 months.

Weather is worth writing down. If it will not start after heavy rain and is fine again once it has dried, or if it went quiet after a wash, put that in with the numbers off the unit — it tells us where to begin. Complete the Repair Form with those details, and the unit can be posted in from anywhere in the UK.

Common part numbers associated with this type of unit