Home › Fault codes › 2A3F (Valvetronic power)
BMW 2A3F: Valvetronic actuator power supply
The Valvetronic motor, which controls engine breathing instead of a throttle, has lost its power supply. Expect limp mode. Check the relay, fuse and motor.
Last updated
Codes on this page
| Code | Definition | Source |
|---|---|---|
| 2A3F | Valvetronic, actuator: power supply | E90Post owner thread |
| 2A77 | Controller, internal error: Valvetronic output stage | E90Post owner thread |
P-codes are the generic OBD-II codes any reader shows. Six-character and four-character hex codes are BMW's own, read with a BMW-capable scanner; the wording is BMW's, from the source shown.
What it means
Valvetronic engines such as the N52 control intake valve lift with an electric motor on the cylinder head. 2A3F means the DME sees no power at that motor's supply. The engine falls back to limp mode, often with mixture codes as side effects. This page is based on an owner's diagnosis linked below; we haven't found a BMW bulletin for it.
Can I keep driving?
Only gently, to a shop. In the reported case the engine idled but wouldn't rev past about 2,000 rpm and was limited to about 10 mph in gear.
Usual causes on BMWs
| Cause | Cars most affected | What you notice | Evidence |
|---|---|---|---|
| Valvetronic motor shorted, taking out its relay | N52K (E91 reported) | No power from the Valvetronic relay; the motor had an internal short. Replacing the motor and the relay, then running the adaptation, fixed it. The 29E0/29E1 mixture codes were side effects. | Owner report |
| Fuse or wiring | N52 and other Valvetronic engines | Check the Valvetronic fuse and the supply from the electronics box. | Owner report |
A bulletin isn't a recall and doesn't mean your car has the problem; open it for the exact models and build dates.
What to do
- Check the Valvetronic relay and fuse before replacing the motor or eccentric shaft sensor.
- Run the Valvetronic adaptation after any repair.
Warnings it can bring up
Related codes
Other BMW bulletins that mention it
- SI B12 19 16 N63R - valvetronic actuator position faults caused by poor harness connection G11, G12 · Aug 2016
- SI B12 04 15 DME Internal and Valvetronic Faults Set at Cold Ambient Temperatures E46, E60, E70, E71, E72 and others · Jan 2015
- SI B12 02 24 Voluntary emissions recall 24e-a02: valvetronic G05, G06, G07, G09, G11 and others · Oct 2025
- SI B12 28 19 The MIL may be illuminated by erroneous valvetronic faults G05, G06, G07, G14, G15 and others · Nov 2019
- SI B12 13 18 DME fc 21a02d – combustion control: valve lift at idle G01, G11, G12, G20, G30 and others · Feb 2021
- SI B12 05 17 N63T – check engine light (MIL) on after a hot engine restart F01, F02 · May 2017
- SI B12 04 18 Buzzing noise from valvetronic motor before or after engine operation G12, G30, G31, E90, E92 and others · Jul 2018
- SI B11 06 16 Engine no-start E46, E60, E61, E70, E82 and others · May 2016
14 of the BMW bulletins we hold mention it in their text; these are the closest matches.
Sources
- E90Post owner thread: limp mode with 2A3F, 2A77, 29E0, 29E1 (N52K) and the fix
- NHTSA: BMW technical service bulletins and recalls by VIN
Bulletins are cited in the tables above. Explanations are ours; where a source is an owner report rather than BMW, it is labelled as one.