Bosch BMS46 Engine ECU Repairs

Type: Bosch Engine Management
Fits: BMW 316i / 318i
Engines: E36 / E46
Year: 1998 – 2004
Ref: ECUT320195

Note: This ECU may also fit other models.

Finding 0 261 204 420 on the case of a BMW engine ECU gets you halfway to identifying it. The other half is the BMW DME number on the same unit, because on this Bosch BMS46 it is the DME number, not the Bosch one, that tells one control unit from another.

Below we set out why the Bosch number stops short here, which DME number our record pairs it with, the four-cylinder BMWs it is recorded in, what to do when your DME number differs, and how we repair the unit once it reaches us.

Why the Bosch number only gets you halfway

On many of the engine ECUs we list, the ten-digit Bosch reference does most of the identifying. Seven sources record 0 261 204 420 as a Bosch BMS46, so here it does tell you which family of engine management you are holding.

What it does not do is single out the unit. Twelve independent sellers list 0 261 204 420 beside BMW DME 1 430 940, yet three other sellers each record the same Bosch number beside a different BMW DME number, and no two of those three agree.

Those three records do not say whether each describes a separate unit or a slip in one listing, and we do not guess. They do settle one thing: a Bosch number that can sit beside more than one DME number cannot be the last word on which unit you have.

The pairing on record: Bosch 0 261 204 420 with DME 1 430 940

The pairing we hold is Bosch 0 261 204 420 with BMW DME 1 430 940. It is the single row in our table, and it is the reading of this Bosch number that twelve independent sellers agree on, against one seller apiece for each of the alternatives.

Read both numbers from the unit itself rather than from a listing or an invoice. If the case shows 0 261 204 420 and the DME number reads 1 430 940, the unit is the one this page covers.

Four-cylinder BMWs only: E36 and E46 316i and 318i, and the Z3 1.9

Every corroborated record places this unit on BMW’s M43 four-cylinder petrol engine. The E46 318i is the most often recorded, in seven sources, and the E46 316i appears in four. The E36 316i and 318i appear in six, and the Z3 1.9 in two, the least documented of them.

There is no six-cylinder in that list, which makes the engine a quick first check. If your BMW has a six-cylinder engine, look for its unit among BMW engine ECUs beyond the M43.

The model narrows the search without finishing it. An E46 318i makes 0 261 204 420 worth looking for without confirming it, and even a matching Bosch number still leaves the DME number to check.

When your DME number is not 1 430 940

This is the case the page is built around. A unit showing 0 261 204 420 with a different DME number is not the pairing in our table, and we will not treat it as the same unit on the strength of the Bosch number alone.

That does not rule it out. Give us the DME number as it appears on your unit, alongside the Bosch number, and our engineers confirm coverage for that specific unit rather than assuming it matches the one listed here.

The same goes for a worn or partly unreadable label. Send what you can read and say which characters you are unsure of, because a guessed digit in the DME number does more harm than a gap.

A Bosch number other than 0 261 204 420 means a different unit and a different page, and if the vehicle was not a BMW at all, start from our engine ECU repairs beyond BMW.

How we repair a Bosch BMS46 once it arrives

We work as a mail-in service covering the whole of the UK. Every unit is repaired in-house, by our own engineers, in our own UK workshop and on our own equipment, with no part of the job sent elsewhere.

Once it reaches the workshop, your BMS46 is logged, checked by eye and tested electrically before diagnostics aimed at its particular fault begin. We come back to you with what we found and a quote, and nothing chargeable happens until you authorise it.

The repair itself is done at component level, under a microscope with temperature-controlled rework equipment, and is directed at the part that failed rather than at the whole unit. The BMS46 must pass final testing before it is returned, and the specific repair carried out is covered by our 24-month warranty.

Sending your BMS46 to us

With the unit out of the car, go to the Repair Form and quote the DME number exactly as printed, together with 0 261 204 420, the model it came from and a sentence on how the fault shows itself.

The pairing we hold for this Bosch number is listed below.

Common part numbers associated with this type of unit