VW / Audi / Seat / Skoda (VAG) Magneti Marelli 4TV Engine ECU Repairs

Type: Magneti Marelli
Fits: VAG – Audi / Seat / Skoda / Volkswagen (VW)
Fuel: Petrol
Ref: ECUT212195

Note: This ECU may also fit other models.

The Magneti Marelli IAW 4TV is a petrol engine ECU recorded in the Volkswagen Polo 1.4, the Seat Ibiza 1.4, the Seat Cordoba and the Skoda Fabia. We repair all twelve units in the table below at component level, in our own UK workshop. A repair runs most smoothly when the right notes are made before the unit leaves the car, so this page covers what to check first, what to copy down, and how to send the 4TV to us.

Confirm the fault before the 4TV comes out

An engine ECU often takes the blame for a fault that starts somewhere else, so rule out the simpler causes first. Scan the car, record every fault code, and clear up anything that points to a sensor, a coil or the wiring before suspecting the unit itself.

If the scanner cannot talk to the ECU at all, check the relevant fuses and the engine control relay, then test the voltage supply and wiring to the unit against a wiring diagram. For a misfire, the coils, HT leads and injectors deserve a look before the ECU does.

Then write down what the car is doing, in your own words. Limp mode, the engine management light staying on, a non-start or a fault that comes and goes all send our diagnostics in different directions, and the fault codes you recorded belong on the same note.

Copy both lines from the 4TV label

The label carries two references for the same unit. One is the Marelli designation, IAW 4TV followed by a full stop and two letters; the other is the Volkswagen Group number, 036 906 034 followed by two letters. On every unit in our table the letters match, so IAW 4TV.KG pairs with 036 906 034 KG.

Copy both lines in full all the same. A scuffed or half-hidden letter on one line can be checked against the other, and several 4TV units differ by a single letter, such as GQ and GS, HA and HG, or KA, KC, KG and KK. Each is a separate unit, so a photograph of the label is worth taking alongside the written note.

Write down the car and check it against the label

Take the make, model and engine size from the V5C or the service history rather than from memory. Then compare the label with the cars each 4TV unit is recorded in.

Five units are recorded in the Volkswagen Polo 1.4: IAW 4TV.GQ, 4TV.GS, 4TV.JC, 4TV.KG and 4TV.KA. JC and KA are recorded as 16V.

Five are recorded in the Seat Ibiza 1.4: IAW 4TV.HA, 4TV.JG, 4TV.KC, 4TV.KK and, again, 4TV.KA. JG is recorded as 16V. HA is also recorded in the Seat Cordoba, the only unit in our table tied to that car. KA is the one unit recorded under both marques, so a KA label is consistent with either car.

Two are recorded in the Skoda Fabia: IAW 4TV.HG and 4TV.JE. On a Fabia, the car and the full label are what we check the unit against, so record both with care.

If the car and the label disagree, say so on the Repair Form before anything is posted; a unit that does not match its car is better queried now than discovered on our bench.

If the car is not one of these, or the label does not begin IAW 4TV, the unit belongs on a different page. For a Volkswagen, start with our map of Volkswagen engine ECUs; for a Seat, browse the Seat engine ECUs; for a Skoda, try the Skoda engine ECU shelf. Other makes sit under the root of our engine ECU repair pages.

Note the engine code if you have it

The engine code is a useful third note, though on this family it confirms more than it decides. BKY is recorded against three 4TV units: GS and KG in the Polo 1.4, and JG in the Ibiza 1.4. Because BKY sits behind three different units across two marques, the code alone cannot pick one out; the label does that.

For the other units we do not state a code. Write down whatever the car’s records show and leave the matching to our engineers, who check it against what is recorded for the unit before anything travels.

Posting the 4TV, and what happens next

We work as a mail-in service across the UK. Before anything goes in the post, send us a Repair Form carrying those notes: the two lines from the label, exactly as printed, the car and engine size, the engine code if you have it, the fault codes and what the car is doing. Our engineers then confirm the unit against the table.

When the unit arrives, it is logged, inspected and electrically tested, then taken through diagnostics aimed at the fault on your note. Repair work is carried out at component level under a microscope with temperature-controlled rework equipment, and the unit is finished only when it passes final testing.

We contact you with what we have found, and no chargeable work starts until you authorise it. Because the fault is repaired rather than the ECU replaced, the 4TV that returns to the car is the one you took out, and the repair carries a 24-month warranty.

The twelve 4TV units are listed below with their Marelli numbers, their Volkswagen Group numbers and the 24-month warranty that applies to each.

Common part numbers associated with this type of unit