20v auto not kicking down.

[cadiddy]

Recently my 20v auto coupe has developed a shifting fault with the auto box, it doesn't want to kick down when in drive, it'll shift down under braking, and if shifting manually. Oil level is bang on, filter was changed ~2000 miles ago. Also seems to slip a bit under hard acceleration between 1st and 2nd.
Any tips?

[UrS4boy]

I would have to suspect that the signal that should tell the Autobox that it needs to kick-down is not getting to it. This will either be a mechanical switch associated with the position of the accelerator pedal or a vacuum switch based on engine vacuum associated with the vacuum that results (or not) when you mash the pedal to the floor, i.e. less vacuum. But then again, I am just guessing on this.

Time for some help:

[UrS4boy]

C4 AutoTrans Wiring Diagram

This might or might not help:

In the lower left corner it mentions a switch on the throttle body *OR* cable which has a grey/yellow wire that goes to Pin 41 of the Transmission Control Module (TCM):

[cadiddy]

Thanks for the replies bud I'll RTFM and have a look for that wire as well. Will let you know what I find if I find anything

[popdemonic]

on the throttle cable,there 's a kick down switch be mounted on the firewall.if the cable being adjusted too stiff.the kick down switch will be broken and caused the kick down function won't be working.check it out.i had 3 auto throttle calble broken on this switch when i adjust the cable too stiff.

[UrS4boy]

i had 3 auto throttle calble broken on this switch when i adjust the cable too stiff.

Pop: what do you mean by "too stiff"?

[UrS4boy]

Throttle cable part numbers and automatic kick-down switch

on the throttle cable,there 's a kick down switch be mounted on the firewall.

Pop: Does the switch look like item 28 in this diagram? (I can't find the PN for it. Do you remember what the PN is?)


BTW: The UrS LHD throttle cable (Item 34) PN is 4A1723555P, RHD = 4A2723555H

[popdemonic]

No Dave,the retaining clip(No.14) is the adjuster how fast the kick down switch response.the more you stress the cable out,the faster the kick down response.the kick down switch is assembled on the throttle cable with the big rubber boot and electrical switch inside.the switch will be mounted on the firewall with 2wires iirc.this switch will be only working when you depressed the gas pedal all the way down.inside the switch, there's a very stiff spring pushed against the switch,if you adjust the clip no.14 too tight(more stress on the cable),you increased the preload stress on the switch and finally the switch broken off.i had 3-4 throttle cables with the same bad switches.

[cadiddy]

I think the issue in my case maybe something different as the kickdown is not working at all it wont even kickdown 1 gear when you depress the pedal halfway or more. I think it may be throttle body as Dave suggested earlier.

[UrS4boy]

I think the issue in my case maybe something different as the kickdown is not working at all it wont even kickdown 1 gear when you depress the pedal halfway or more. I think it may be throttle body as Dave suggested earlier.

I really think it is going to be the kick down switch or the wiring between the switch and the TCM (transmission control module).

[popdemonic]

normally if the TCM is culprit or something's going wrong on the drivetrain system.it will defo go into limp mode.using VAG-com to check if the drivetrain throws you any faults if not i doubt your kick down switch is malfunction.

[74rsman]

Hi. Has anyone got a higher resolution image of the tcm wiring diagram for the above for a 1996 s6 please. Also does the s6 have a kickdown button as i cant find anythjng on the pedal or bulkhead. I assume the computer just calculates kickdown from tps and load. The only thing i do see is a prodder on the end of the throttle cable that pokes a microswitch on the side of the engine, mounted in a big rubber cover. This is pressed at 100% throttle, could this be it? Image and info appreciated thx


Sent from my iPhone using Tapatalk

[74rsman]

Found it. Inside the car right up where the cable goes through bulkhead, the foam padding is hiding it.