XC90 (P2) Driving Light Install (inc. how to HACK a P2 Switch to AUX function)

This is a relatively simple install option without using the genuine accessory kit. Either method provides legally configured switching to disable the lights when the headlights are dipped without defacing the interior to add a switch and wiring through the firewall.

OPTION 1 - Without OE Switch (using front Foglight switch inside the vehicle - disables fog lights).
Only applicable with front OE fog lights (not day running lights)
Modified Wiring
A control relay is added to that supplies 12v from high beam to the driving light relay when the fog light switch is on.
  • 2 x relays
  • Spade lugs
  • hookup wire (1mm2 and 3mm2)
  • Disconnect both front fog lights.
  • Remove LHS headlight
  • Identify high beam circuit and splice a wire to supply the "control" relay (A1)
  • Replace headlight
  • Route fog light loom, and light cabling into engine bay (refer to revised circuit and pic of installation below).
  • Cut down 2 thick spade lugs to 4mm wide
  • Using spade lug, connect fog light (+) to control relay (terminal 1)
  • Using spade lug, connect aux lighting plug (+) to aux light relay (terminal 30)
  • Ground both relays (terminal 85) to chassis (-)
  • Connect control relay NO contact (terminal 87) to aux light relay coil (terminal 86)
  • Connect lights using 3mm2 cable to (terminal 87) and chassis ground point in engine bay.
  • Put 15A fuse into position 2 of engine compartment fuse box.

OPTION 2 - With OE Switch (hacking another P2 switch to function as an AUX light switch).

You can either use a genuine AUX switch (no longer listed) or hack your own from another switch from any P2 car. Credit is due to some switch tear downs on a Russian forum, google translate and a discussion thread at swedespeed.com.
Any switch will do - they are all internally reconfigurable. Diodes (D1-D5) must be changed to match those in the following picture (i.e. only D4 and D5 present for the AUX function).
Disassembly of the switch and surface mount soldering is required (i.e. A fine tipped soldering iron, tweezers, solder wick and magnifying glass).


P2 switches have different diodes in place (D1-D5), LED's and labels.
  • Window Lock (01111) : (orange LED)
  • DSTC (11101)
  • Rear AC (01011)
  • Mirror (01001)
  • Park Assist (11001) : (no LED)
  • Interior Alarm (10011)
  • AUX lights (00011)

Insert the switch following the OE instructions. A power cycle (full reset) is required.
I used a Park Assist switch (re-labelling the switch is still WIP).
(Note that a DSTC switch can also be added to later model without one).

Wire the lights as per the OE instructions (unmodified circuit above).
  • Cut down 2 thick spade lugs to 4mm wide
  • Using spade lug, connect aux lighting plug (Pin 1) to to aux light relay (terminals 30 and 86)
  • Using spade lug, connect aux lighting plug (Pin 2) to aux light relay (terminal 85)
  • Connect lights using 3mm2 cable to the aux light relay output (terminal 87) and chassis ground point in engine bay.
  • Put 15A fuse into position 2 of engine compartment fuse box.

Hardware & Tools
  • 1 x light bar frame hardware (Custom, Supercheap or equivalent)
  • 1 x Volvo Accessory Installation Instructions Link
  • 1 x 7mm drill bit
  • 1 x 13 mm spade bit (centre point filed to <7mm) instead of P/N 8633152 stepped drill bit ($2 specials tray at mitre10)
  • 4 x 12mm steel tube spacers (44 mm long)
  • 4 x 65mm long metal screws
  • Basic tools
Note that to comply with ADR's, measures must be taken to prevent the mounting from hooking or grazing other road users / pedestrians. This is usually taken to mean that:
  • Exposed edges need to be chamfered and free of burrs or sharp edges
  • Forward facing edges must have radii not less than 5mm
  • Open ended frame members are not permitted
Install light bar frame using same technique described in the Volvo accessory instructions
  • I suggest using 4 spaces (rather than 2 in the OE kit) to provide greater rigidity
  • Centre the bar and drill 4 pilot holes (distributing the 4 spacers evenly vertically and horizontally)
  • Check that the steel bumper bar is behind all pilot holes! (its large and difficult to miss)
  • Use the modified spade bit to cut hole for spacers. Note that the plastic bumper is double skinned and a large twist bit wont remove the rear skin against the steel bumper
  • Insert pre-cut tube spacers into large holes
  • Fix in light bar frame in place using metal screws

This light bar is quite rigid (no wobble and no dodgy stays as required in the OE kit!). It has seen 20,000 km so far and took a few hard knocks that bent the tube without coming loose.

The Result

Let me know if something is unclear and I'll edit or provide further pics.


  • Ex850RSnoopy @Ex850R Somewhere Over the Rainbow. Melbourne.
    Silicon tape is the biz , or liquid "tape".
  • Updated :
    - text updated
    - Details of how to hack a P2 switch to use OE wiring and CEM programming added (VIDA not required)

    P2 switches can be had relatively economically now from second hand sources by obtaining the climate module. This will normally yield you 5 switches, 7 way trim and some spare globes.
    A bonus for later models is a DSTC switch which can be added and will work without any programming.
  • interesting.... I could use this for an AUX power supply....
  • edited June 2018
    interesting.... I could use this for an AUX power supply....

    Only switches on when high beam active.

    For other applications https://volvotech.eu/spider-xl can be used with some unused switch functions (eg alarm sensitivity, AUX without lights installed ore even keypad combinations) to control discrete I/O. Only downside is they need to program it for you (i.e. you need to nominate logic you want programmed).
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