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I'm about to attempt a PCM4 retrofit on my 991.1 GT3 and would like to document the process so others can see what's involved. Note this isn't a how to, this post serves as a journal of my progress. I've done this before in my Audi, and the PCM4 is Audi's MIB2 hardware running Porsche software, so I have high hopes that this is possible.
To start off, here's the parts I ordered and cost.
PCM4 Central Computer + Display w/ GSM, NAV, SXM, AM/FM, CarPlay, $700
Quadlock Female to Male Extension Cable (to rewire into PCM3.1 to PCM4 adapter harness) - $15
6-Pin TE MultiLock Connector (for wiring Quadlock grey block to display panel) 174044-2 $4
Fakra HSD Female to Female Cable (for LVDS to display panel) $19
Cellular antenna, Fakra A connector $5
Sirius XM antenna, Fakra A connector $11
Fakra B (dual) to Fakra A (single) adapter cable (to adapt AM/FM and Cellular to existing antennae) 2 @ $8ea
MOST Fiber Optic Y Splitter Cable $8
MOST Fiber Optic Extension Cable $8
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Total BOM $786.
PCM4 is vastly different from PCM3.1 so this is not a drop-in replacement. I will be re-wiring essentially the entire connector block, and anybody that chooses to do this retrofit, please ensure that you're comfortable with electrical work. Once the unit is wired, it must be coded to the car so it's properly configured for any installed equipment, displays the correct model on boot-up, etc. Wiring and coding information will follow in a future post once I receive and re-wire the adapter harness to install this head unit in my car. Wiring diagrams are available via PIWIS TSI.
In my previous retrofit attempts, I have had to bring the car into a willing dealership to have component protection deactivated, the cost is typically a few hours of labor, but I'd like to avoid the dealership altogether for this retrofit. So while I am awaiting the parts from China, I have the PCM4 system out on the bench and am in the process of pulling firmware from the NOR and eMMC for further examination.
For others who would like to examine the inner workings of PCM and contribute, I have attached some pictures of some pinouts that I've traced out for UART and the eMMC TPs. The system runs QNX, and the UART interface prompts for a login which I do not know the password for. I'll find the hash from the eMMC dump and post the password once it's found (the password does change with each release)
But isn’t the communication protocol different on the 991.2? I thought that was the reason the .2 MF steering wheel cannot be retrofitted without an adapter translating the communication. That said, the new interior mirror can be retrofitted without issues. Maybe you can shed more light on this.
I am curious where you obtained a PCM4 so cheaply. They seem to run $2-3K on ebay lately.
eBay, the seller had the whole assembly listed under the display unit part number, and it was priced as only the display unit. You can very likely flash the software on an Audi MIB2 box over to Porsche's firmware, since the hardware is identical, but you'd still have to source a Porsche display.
Originally Posted by Dom991.1
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I have access to a PIWIS II & two 991s (2013 & 2015) - if the something I can check/verify for you, PM me.
Appreciate it, do you have access to pull the PCM feature enablement codes from a couple VINs, or is your PIWIS offline only?
Originally Posted by RYE
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But isn’t the communication protocol different on the 991.2? I thought that was the reason the .2 MF steering wheel cannot be retrofitted without an adapter translating the communication. That said, the new interior mirror can be retrofitted without issues. Maybe you can shed more light on this.
I'm not familiar with that but I tried looking over the wiring diagrams for both PCMs and don't see anything directly related to the wheel, so it must communicate over CAN bus, or it is muxed with another signal (instrument cluster?). IMO, the most likely scenario is that it's an issue with PCM3.1 not supporting the newer MF wheel, it might also be that the CAN gateway is incompatible with the new components. However, I wouldn't suspect a CAN gateway retrofit is needed at this point, since according to Porsche's parts catalog it looks like the 991.1 and 991.2 use the same part (on my car it's 7PP-907-530-L).
I left all of the parts at work so I'll have more updates this week, should have the firmware pulled tomorrow to take a look at how the system functions.
Parts got delayed, the main wiring harness is stuck in customs still but the board that will allow me to dump the firmware from the PCM4 arrived today. I'll have to look at the firmware dump and find out how to bypass component protection and feature activation codes, but I won't be able to do much work on this until mid next week. More to follow soon
you are doing great job
also i have plan to retrofit PCM4 cayenne 958.2 to cayenne 958.1
will you please share more data on your work ?
also please check your private message
regards
05-11-2019, 02:51 AM
Retrofitting PCM4 in a 991.1
