BMW E90 3er DME-Steuergerät Codierung und Austausch-Kompatibilität
The BMW E90 3-Series uses a Siemens or Bosch DME (Digital Motor Electronics) as its primary engine control unit, and replacing it is not as simple as swapping a part and turning the key. Every DME is programmed with software tied to the engine variant, fuel type, emission standard and chassis, and it also carries the vehicle’s immobilizer data through the CAS3 module. A used DME that has not been correctly matched and coded will prevent the engine from starting or will run in a highly limited limp mode. Understanding compatibility before purchasing a replacement saves significant diagnostic time and avoids the frustration of installing a part that the vehicle refuses to accept.
Which DME Variants Exist in the E90?
The E90 3-Series was produced from 2005 to 2011 across saloon, touring (E91), coupé (E92) and convertible (E93) body styles, all sharing a common electronic architecture. Engine variants determine which DME generation the vehicle uses:
- N46B20 / N46B20B — 2.0-litre four-cylinder petrol engines used in 318i and 320i variants up to around 2007, managed by Siemens MSV80
- N52B25 / N52B30 — 2.5 and 3.0-litre six-cylinder petrol used in 325i and 330i, also MSV80
- N43B20 — 2.0-litre direct injection four-cylinder (320i from 2007 onward), managed by Bosch MEVD17.2
- N53B30 — 3.0-litre direct injection six-cylinder (330i post-2007), managed by Bosch MEVD17.2.G
- M57N2 — 3.0-litre diesel in 330d variants, using Bosch EDC17CP02
- N47D20 — 2.0-litre diesel in 318d and 320d, using Bosch EDC17C06 or EDC17C41
These are not interchangeable. A DME from an N52 engine cannot be flashed to run an N43. The hardware must match the specific engine and emission variant the vehicle left the factory with.
Relevante Fehlercodes
When a DME is failing or incorrectly matched, certain fault codes appear in BMW ISTA or INPA diagnostics:
| Code | Beschreibung |
|---|---|
| 2A00 | DME internal fault — hardware defect suspected |
| 2F2B | CAS/DME synchronisation fault — immobilizer mismatch |
| 2F4A | CAS3 communication to DME lost |
| 2912 | Engine control module EEPROM fault — internal memory error |
| 29DC | Variant coding fault — incorrect software variant for installed hardware |
| 2A82 | DME supply voltage outside operating range — check wiring before replacing unit |
Before condemning the DME itself, it is worth checking supply voltage, ground connections and wiring harness continuity at the DME connector. A voltage drop fault or corroded ground can generate codes that look like an internal DME failure but are entirely external in origin. For comparison, see BMW E90 3-Series DME Engine Control Module Faults and Repair.
OEM Part Numbers — E90 DME Examples
The following OEM numbers represent realistic DME references for common E90 variants. Always verify against the exact engine code, software version and vehicle build date before purchasing.
| Engine | OEM Number | DME Type |
|---|---|---|
| N46B20B (318i/320i) | 7 562 937 | Siemens MSV80 |
| N52B25A (325i) | 7 589 110 | Siemens MSV80 |
| N52B30A (330i) | 7 589 117 | Siemens MSV80 |
| N43B20A (320i DI) | 7 811 227 | Bosch MEVD17.2 |
| N47D20A (320d) | 7 804 381 | Bosch EDC17C06 |
| N47D20C (320d LCI) | 8 514 482 | Bosch EDC17C41 |
These numbers are a starting reference. BMW DME variants are heavily software-specific and even within one engine code there can be multiple hardware revisions. The full fourteen-digit part number stamped on the existing DME should always be the primary reference when sourcing a replacement.
Coding and Immobilizer Synchronisation
This is the step that catches many owners off guard. On the E90, the DME and CAS3 (Car Access System) module are paired cryptographically. When a replacement DME is installed — even one with the correct OEM number — it must be synchronised to the vehicle’s CAS3 using BMW ISTA/P or equivalent software capable of performing ISN (Individual Serial Number) alignment.
Without this step, the engine will crank but will not start because the DME does not recognise the key as authorised. This is commonly misread as a failed replacement unit when the part itself is perfectly functional. The synchronisation requires workshop-level access and cannot be performed with generic OBD tools.
Additionally, after coding, the DME requires a variant coding session to set the correct market, emission standard and equipment options for the vehicle. Skipping this produces code 29DC and can result in restricted fuelling strategies or incorrect idle behaviour. A related diagnostic guide is Fehlerdiagnose des DME-Motorsteuergeräts beim BMW E90 der 3er-Reihe.
Used OEM Replacement Considerations
A used OEM DME from a matching E90 is a cost-effective route provided the OEM number is genuinely correct and the unit comes from a vehicle with the same engine, gearbox type and build year range. The ISN can be reset or aligned during coding, making used units viable as long as the hardware revision matches.
Remanufactured units are available and usually come pre-coded, but they require the workshop to supply the vehicle’s ISN data for the CAS synchronisation to be completed remotely before shipping or on arrival. Some suppliers perform this as part of the service; verify this before ordering.
Avoid purchasing E90 DME units without a clear OEM number. Listings describing only a general engine code are insufficient — two 320d variants from different production years may use entirely different Bosch hardware that cannot be flashed interchangeably.
Affected Model Years and Variants
The E90 platform covers 2005 to 2011 for the saloon, with E91 Touring sharing the same electronic architecture. E92 coupé and E93 convertible use the same DME families for matching engine codes. Pre-LCI vehicles (2005–2008) and LCI vehicles (2008–2011) may use slightly different hardware revisions of the same DME family, particularly for the N47 diesel. Build date is a more reliable guide than model year when sourcing replacement electronics.
Häufig gestellte Fragen
Can I fit a used E90 DME without coding?
No. A used DME will not start the engine without CAS3 synchronisation. The ISN alignment is mandatory and must be carried out with BMW-capable diagnostic software. The part may be physically correct but the vehicle will remain in a no-start condition until coding is completed. For additional context, read BMW E90 3er DSC Modul Teilenummern und Kompatibilitätsleitfaden.
Will a DME from an E91 fit an E90 with the same engine?
Potentially yes, if the OEM part number matches exactly, the engine code is identical and the build date falls within the same production range. The body style itself does not affect DME compatibility, but equipment differences such as gearbox type or optional systems can produce variant-specific software differences. Confirm the full part number before purchasing.
What happens if the wrong DME variant is installed?
The engine may crank without starting, or it may start briefly and immediately shut down. Fault codes 29DC and 2F2B are typical. In some cases a wrong-variant DME will run with significant fuelling or timing errors that cause rough running and limp mode. The unit must be replaced with a correctly matched one — software flashing cannot change the base hardware variant.
Does the N47 diesel DME fail more often than the petrol units?
The Bosch EDC17 units used in N47 diesels are generally robust, but they are vulnerable to moisture entering through a damaged wiring harness grommet near the DME housing. Water ingress causes internal short circuits and EEPROM corruption. The N47 engine itself had well-documented timing chain issues that could cause hard engine damage events, which sometimes takes the DME with it through electrical spikes. Inspect the harness carefully before assuming the DME is the root cause.
How do I read the ISN from a faulty E90 DME?
If the original DME is still partially functional, BMW ISTA or INPA can read the ISN directly from the unit. If the DME is completely dead, the ISN can be recovered from the CAS3 module instead, which stores a copy. A specialist with the correct tools can extract the ISN from CAS3 to allow a replacement DME to be synchronised without needing the original unit at all.
Geprüfte OEM-Elektronikteile und -Module finden Sie unter:
https://giantparts.eu/
