Heading north (Hope to Merritt):
Take exit 221 (Falls Lake Road) and go back under the hwy. Follow the road to the parking lot and keep driving straight through onto the dirt "road". The highway exit is at N 49° 36.811' W 121° 02.938'
Keep driving...
You will eventually end up at exit 228 (Coquihalla Lakes Road), on the other side of the toll booth.

You will drive a fairly off-road route (at times). There is a "road" to follow that near the end joins a good gravel road. But it's bumpy! We came shortly after some rains, so lots of big ruts and wash outs. My five year old kept asking, "Are we going to fall off the cliff?" But it's quite safe, if you are a safe driver. The Jammy Dodger did excellent. Took us about 30 minutes to traverse the route.
WARNING - close tree branches adorn parts of the route, and the Jammy Dodger got her stripes - lots of them nose to tail - that will have to be buffed out. I'll be a little more careful next time.

You will pass near these waypoints:
N 49° 36.601' W 121° 03.336 (near Falls Lake Road)
N 49° 37.409' W 121° 03.388' (off road)
N 49° 39.236' W 121° 01.154' (near Coquihalla Lakes Road)
Heading south, obviously reverse the directions.

Some pictures of the nicer parts of our short adventure:
I can only add seven pics per post, so next post will have the rest.