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+--- Thread: IHU (/showthread.php?tid=519)
RE: IHU - thermal-fixity - 11-03-2025
I've swapped my 3.0 IHU with a 3.2 system and the subwoofer stoped working. Anyone had similar experience?
For reference, I've flashed it with my config and tried different coding like HP, HK with and without subwoofer. Left the car to sleep multiple times but nothing helped to get the subwoofer back. One interesting thing I noticed is that my dash center speaker started to play with the new IHU (I retrofitted that speaker but it didn't play with my old IHU and my current AUD).
As I understand the IHU is connected to AUD through the optical line, perhaps Volvo have changed signal encoding in the newer audio system versions
@imay2023, @power6 any chance you've seen this before?
RE: IHU - thermal-fixity - 11-03-2025
My swap details
- Original IHU: HW 3.0 Sensus 31483226 from 16-03 (XC90)
- New IHU: HW 3.2 Sensus 32343493 from 21-03 (XC40). This unit came with 128GB SSD and without the CD plug (a green FAKRA connector in the back)
Everything worked plug and play, just needed to flash the new IHU with my config. I have not tested installing apps/updates since I don't think this is going to work as the others were saying. My car is 2016 with a 3G modem so I can't use the app ether way, also I mostly use CarPlay so don't really care about the apps/updates. Another nuance, my original microphones did not work (as expected) and I had to swap them with the new ones.
Microphones
IHU 3.0 (and 3.1 I think) uses analog microphones that are connected to the IHU via 3 coaxes. From my observations, it seems like the analog microphone group takes the following pins:
- B1-5, B7, B15-19, B25
IHU 3.2 uses digital microphones that are connected to the IHU via 2 wires (all 3 microphone signals utilize the same wires). The pins are:
- B8, B9 (these pins were empty in my IHU B plug)
For reference the B IHU plug is a gray plug at the back of the IHU with the most contacts. It's a bit smaller than the other plug gray plug.
Parts
I bought all parts from eBay:
- $120 - IHU
- $100 - digital microphones with the roof harness. Each microphone is typically $30, there're different part numbers for the left and right units since there're 2 microphones on the driver's side and 1 on the passenger's side.
My new microphones and harness came from a 2019 XC90, the harness was made on 15/12/2018. The part numbers are:
- 32265871 - Left
- 32265869 - Right
- 32247300 - harness
Making Microphones Work
- I cut out the mic plugs and the IHU pins from the harness. I think buying a harness was an overkill, just having microphone plugs and a couple of pins would've been sufficient. Regarding the pins, you could also reuse the pins from the digital microphones if you know how to pull them out safely (I always mess this up, please post a link if there is a thread explaining how to properly pull out pins from a Volvo-like plug).
- The analog microphones are connected via FAKRA plugs. I cut the 2 of those plugs on the driver side and used the core center wires for running the new digital microphone signals from the driver side microphone. So that, each coax cable caries 1 digital microphone signal via its center wire. To note, since I already had that part of the harness the driver side microphone was already connected to the passenger side microphone.
- Those 2 coax core wires were originally connected to B1/B2 on the IHU. I cut those wires and reconnected them to B8, B9 correspondingly. I used the B8 and B9 pins from the roof harness.
I plugged everything back in and the microphones worked. During the first test call the person on the other side said they were hearing me clearly but also slight echo of their voice. Not sure if that's the issue with the microphones/wires or something else.
Fist Impressions
- The interface is so much snappier, day and night.
- The backup camera turns on practically instantaneously on a cold start (previously I had to way seconds if not a minute).
- The camera button in the menu brings up a 360 view by default now (so nice!).
- The UI mostly has no changes, although some minor visualization notes might have changed but that's hard to tell.
- CarPlay works. I had CarPlay retrofitted for free by the local Volvo dealership a couple month back.
Unresolved Issues
- As I said in my previous post, the subwoofer stopped working. Background: I've retrofitted a subwoofer and a center dash speaker. The subwoofer worked with my original IHU and the center dash speaker did not. My audio system is High Performance, the assumption was that the center speaker didn't work because my AUD doesn't have enough channels.
I've ordered a Harman Kardon amp, hoping it's going to resolve the issue with the subwoofer.