Adding Rear Speakers to a VW T6 OEM Headunit

The Problem

The van had no rear speakers connected despite having an OEM headunit with a multi-pin connector block that carries rear speaker signals. You need to identify which pin positions to use and source connector pins that physically fit the block. Note that the T6 was fitted with more than one OEM head unit — commonly Composition Audio, Composition Media and Discover Media — and pin assignments can differ between them, so the positions below should be verified against the wiring diagram for the exact unit in your van (confirm this applies to your T6 generation).

Solution

1. Identify pin positions 1, 4, 5, and 8 on the OEM connector block — these carry the rear left and right speaker positive and negative signals. Before crimping, confirm the exact channel-to-pin mapping (rear-left positive, rear-left negative, rear-right positive, rear-right negative) against the wiring diagram for your specific head unit variant (Composition Audio, Composition Media or Discover Media), as the individual pin assignments are not guaranteed to be identical across units (verify pinout before ordering/crimping).
2. Source an ISO 16-pin car audio twin male terminal connector block repair kit. The terminals must match the ISO connector spec to fit the block — a different brand sourced from Amazon did not fit. Search by the ISO 16-pin terminal specification rather than by a specific listing title, as eBay listings expire and titles change (verify part number/SKU before ordering).
3. Slide the purple locking tab out of the connector block before attempting to insert any crimp pins — without doing this the pins cannot be pushed in.
4. Crimp your speaker wire to each pin, insert it into the correct position in the block, then reinsert the purple locking tab to lock all pins in place. The locking tab is a secondary retention mechanism; the crimp barbs hold the pins even without it, so a lost tab is not critical.
5. If steering wheel controls stop working after the headunit is refitted, reseat the UAR plug (the black DIN plug) — it is easily dislodged during removal.