problem reading (3B) wiring schematic

[pfi]

As my (3B) engine wiring is a totaly mess I need to dig deep(er) ...
Found a lot of useful info here : https://www.s2-audi.co.uk/workshop/s.../sc_lookup.htm
but, having problems reading some of the info on the schemas :/

Sample with Z19, G42, G62 and G69 highlighted :
page4x.png

Z19 - Lambda heating

brown/red is : grounded? to B4
grey/red : goes to [17]

G42 - Intake air tmp sender

black/yellow : goes to ECU pin 44
black/violet : goes to [26]

G62 - Coolant tmp sender

red/green : goes to ECU pin 45
black/violet : goes to [27]

G69 - Throttle valve pot

green/blue -> ECU pin 53
red/black -> [51]

what is [17], [26], [27] and [51] refering to ?
my first thought was fuses, but doesn't match ?
pls enlight me

[Error404]

It refers to the track number, along the bottom of the schematic.
e.g. Sw/Li from G62 goes to track 17, joins other sensor grounds in joint E8 in the harness.
Track 51 joins 5v sensor reference at joint D3 etc

[pfi]

hmm
got even more confused :0

If focus on Z19, it has two "lines"

brown/red : earth
grey/red : to [17]

can't find [17] at bottom of schematic, what is [17], where to find ?

[pfi]

Not logic if both brown/red AND grey/red is earth

isn't all at bottom of schema earth ?

[Error404]

Track 17 is on a different page of the schematic. The page shows track 22-34.
Yes the bottom line is chassis ground.

[pfi]

but, how to know what page, I'm lost in space ...

[Error404]

You know how to read a book?
Its like page numbers. All of the schematics you’re need are on S2-Audi

[pfi]

a book missing page numbers ...

[Mikes2]

http://s2-audi.co.uk/workshop/schema...c_3b/page3.png has track 17

[pfi]

so, the numbers on the bottom horizontal line is track-numbers
and, numbers in square-boxes on a schema refers to a track-number
that's logical
but,
if so, the Z19 on https://www.s2-audi.co.uk/workshop/s...c_3b/page4.png cable grey/red refers to track# 17
and on https://s2-audi.co.uk/workshop/schem...c_3b/page3.png track# 17 is coupled to G61 (Knock 1) black wire, and marked with a circkle numbered 138 saying Eart connection
that's not logical
or, is it me being stupid ...

[Mikes2]

If you look on page3 (top), there is a small square box with 34 in it, leading to fuse S25. That corresponds to the Z19 wire that leads to track 17 on page4

[pfi]

Thnx ! that make sense

....
for others needing (more) info, found this, "A demystifying guide to schematics & cabling" :

https://www.s2central.com/S2_Schematics/Schematic_Primer.pdf