No sound or poor sound after a MIB unit swap, retrofit or amplifier change

How to recognise the problem

Symptoms appear straight after a unit swap, retrofit, amplifier change, region conversion, patch or firmware update. Owners report one or more of the following:

• No sound on any source although the volume bar moves on screen, or the volume stays at maximum and cannot be changed.
• Sound only from the front tweeters, only from one side, only from the rear right speaker, or no output from the rear speakers.
• Navigation and phone prompts play from the wrong speakers while music is fine.
• Thin sound with no bass, very low overall volume, or flat sound that needs the volume turned up high.
• Sound menu items missing or greyed out: fader, subwoofer slider, equalizer, Dynaudio or other branded sound menus; or a branded menu shows but presets have no effect.
• Fault entries such as an open circuit to the amplifier, all speakers reported as open wire, an SVM error, a 'control module incorrect' error, or B200500 (invalid data record for audio parameter) on an MST2 unit.
• A subwoofer control that does nothing across its whole range.

Which units are affected

Reports cover VW, Audi, Skoda, SEAT and Porsche units across MIB1, MIB2, MIB2.5, MST2, MHI2, MIB3, RMC, MMI3GP and PCM. The problem is most common when the donor unit came from a car with a different sound system than the target car, for example a unit from a Dynaudio, Canton, Bose or B&O car fitted to a car with standard speakers, or the reverse.

Cars with an external amplifier (Dynaudio, Fender, Beats, Bose, B&O, Canton, Harman Kardon) are also affected after head unit firmware updates, US-to-EU conversions and patches, because the update process can change the amplifier firmware or parameters.

Likely causes

The notes point to five recurring causes, roughly in order of how often they appear:

• Sound system coding mismatch: long coding of the head unit (address 5F, byte 11 in most reports) is set to internal amplifier while the car has an external one, or set to external while no amplifier is fitted. B&O and Bose cars typically need an external MOST setting; Dynaudio, Fender and Beats cars are reported as external BAP.
• Wrong sound dataset: the audio parameter data in the unit belongs to the donor car's speaker layout (for example 9 speakers configured but only 4 fitted, or a Dynaudio dataset in a car with Fender speakers).
• External amplifier parameters lost or mismatched after an update: most reports involve Bose, but also B&O, where the update reflashed the amplifier and left it without matching parameters.
• Component protection still active on the amplifier or head unit, which reportedly gives sound on one side only or no sound at all.
• Coding and adaptations not transferred from the old unit when it was replaced, including channel and speaker configuration bytes.

Before changing anything

Several fixes below involve changing coding, writing datasets or changing amplifier firmware. Before starting:

• Note the current software train of the head unit and the part numbers of the head unit and amplifier (module 47 where present).
• Back up the long coding and adaptations of 5F and any amplifier module. If the old unit is still available, read its coding and datasets first; one owner reinstalled the old unit specifically to copy its coding.
• Where the tool allows it, back up the current 5F datasets (owners used the ODIS module replacement routine for this) before writing anything.
• Keep a stable power supply connected during any flashing or dataset write.
• Record the sound-related options in the car's equipment list so the target configuration is known.

Fix: step-by-step

Work through the steps in order and test after each one. Several owners found that coding alone was enough; others needed a dataset or amplifier parameter write as well.

1. Confirm what audio hardware the car actually has: internal amplifier only, or an external amplifier (and which brand). Check the amplifier part number in module 47 if it exists; reports note that some amplifiers (for example a Dynaudio amp without an index after a G11-to-G13 conversion) will not work with newer software.
2. Check 5F long coding byte 11 (sound system). Set internal when no external amplifier is fitted and external when one is. One confirmed report on train MHI2_ER_AUG22_K3346 used value 02 for an external amp; another confirmed fix on an MIB2.5 in a US Golf with Fender simply selected 'external amplifier' in byte 11. For B&O and Bose, owners chose the external MOST option. Values reported for Dynaudio vary between sources (03 BAP, 05 BAP with presets, 06 in one case), and one owner had to type 05 manually because the option was not listed. Treat these as starting points, not fixed rules.
3. If the external amplifier uses MOST, check that MOST is enabled in byte 19 of the 5F long coding. In OBDeleven the byte can be reached by scrolling down or by switching to the byte view at the top right. Confirmed reports show this also made module 47 visible after a MIB1-to-MIB2 swap.
4. For BAP amplifiers (Dynaudio and similar), owners also set the adaptation Car_Function_List_BAP_Gen2-Amplifier_0x2D to activated and its _msg_bus channel to Databus Infotainment.
5. Check the speaker and channel bytes. Reports mention bytes 4 to 6 for channels and bytes 4 to 7 for the fader. If the fader is missing, confirm rear speakers are fitted and coded. On MST2 with an 8-speaker Dynaudio setup, one confirmed report found the right channel layout by trying combinations such as byte 4 A0 with byte 11 values 01, 03, 05 or 06.
6. Reboot the unit after coding changes. Some owners also let the car sleep for around 30 minutes.
7. Remove or clear component protection on the head unit and amplifier if it is active. A confirmed report of sound on one side only after fitting an amplifier from another car was fixed by turning off component protection on all channels with ODIS.
8. If sound is present but poor, quiet or bass-less, write a sound dataset that matches the car's model, region and speaker configuration, using VCP, ODIS/ODIS-E data transfer on 5F, OBDeleven or similar. One confirmed approach changed only the audio configuration datasets 0x3B00 and 0x3000 in the 5F parameter file rather than copying a full dataset from another unit; 0x3600 is also mentioned for amplifier settings. On MIB3 (Audi A3 8Y, 9VD sound) a confirmed report used datasets 7204 and 7206 together for a retrofit. If the old unit is available, copying its sound datasets while keeping the new unit's own identity data is reported to work.
9. For external amplifiers, the amplifier itself may need its parameters. Reports describe parameterising module 47 with VCP or ODIS, or using official SVM to reload them. A confirmed Dynaudio case with a centre speaker error was solved by loading a 10-speaker parameter file to the amplifier via data transfer.
10. If the problem started after a firmware update on a Bose or B&O car, either restore the amplifier parameters (VCP zdc or ODIS xml format were both reported) or downgrade the amplifier firmware to its previous version. One owner checked the previous version in the update log before downgrading. On Porsche, owners used PIWIS to autocode the Bose amplifier.
11. If coding and datasets are correct and the unit still reports no audio output device, owners concluded the unit had a hardware fault.

Platform-specific notes

Several details only apply to certain units.

• PQ MIB2 standard (Technisat): there is no dedicated sound dataset to load. The Audio Parameter adaptation selects one of three built-in sets (1 to 3), or 0 when an external amplifier is used. An ODIS data loading error when trying to write sound parameters is consistent with this.
• PQ with an external Dynaudio DSP (for example DSP 5C0035680G in a T5.1): owners advise not searching for a dataset and setting long coding to external amplifier instead.
• MST2: one report warns that writing block 3B00 on MST2 corrupted the audio parameters and caused fault B200500; a corrective dataset write was needed afterwards. On MST2 the Dynaudio dataset in 5F reportedly only enables the settings menu; the sound itself depends on the amplifier.
• SEAT: speaker wiring differs between MEN2/MHI2 and MST2, so channel bytes copied from an older unit can send bass to the wrong speaker.
• Audi RMC: after replacing an RMC unit (for example 4G0035192G or 4G0035192H), owners used the ODIS replace-module function and SVM code, and stressed matching hardware to software; K16158 (RMC_EU_K16158) is reported as RMC18EU and P16342 as RMC19EU.
• Audi MMI3GP and RMC with Bose: registering the replacement unit with SVM Online reportedly reloads the Bose parameters.
• Before updating an MHI2 with Bose, owners deselect Bose in the update selection and, according to some, disable MOST in 5F. For B&O on A3/A4/S3/RS3, one source says disabling MOST is not needed; others only require it for Bose on A4 to A7.
• MIB3 T6.1: rear speakers are enabled through the adaptation channel function_configuration_audio-channel.

What did not help

Some approaches failed or were disputed in the reports:

• Loading a generic or another model's Bose dataset. Bose datasets are tuned per model and options such as sunroof, left- or right-hand drive and noise cancellation, so a near match is not enough.
• Using a Dynaudio dataset in a car with Fender speakers, or a Canton car's dataset in a car with standard speakers; sound remained poor even with correct internal coding and component protection removed.
• Uploading datasets meant for an external B&O amplifier to a car with the active sound system only; this gave wrong parameter errors and a phantom amplifier entry.
• Coding only, when the amplifier still had component protection active or the dataset belonged to another car.
• Factory reset and changing the amplifier option on an MHI2 after a US-to-EU conversion did not restore sound for one owner.
• Selecting a Dynaudio profile when the presets have no effect: several owners with amplifier 3AA035466A reported the menu appears but presets do nothing, and no fix was found.
• Changing gateway or bytes 17/18 on a Technisat unit moved between cars did not resolve its behaviour.