Why cant i get to ecu on vagcom or hand scanner, vagcom steps?

[rubjonny]

i would start looking at the jumper box above the fusebox, i recon issue is between that and the immob box, or from there to the diagnostics plug.  since the car will drive a bit before cutting out the box and ecu communications are ok. if the wiring is definitly ok, then there must be a problem with the box itself which is preventing it from communicating with vag-com even though it can still talk to the ecu.

any old immob box will plug into the loom and communicate with vag-com, it will also let you talk to the ecu. just the car wont start due to immob missmatch, and if you dont get one with a matched key chip you cant match it to the ecu

[mark-mk3gti]

hi mate, thanks for your help,  car seems to be running pretty good after crank sensor, hasnt done the cut out thing (touching wood)

gonna have another look at alarm stuff ontop of fuse box when im next off now, towards end of next week.

i dont think the immob is faulty as such, just annoying i cant read codes off ecu at mo, but hopefully its a loose cable to diag socket.. will post again when tried again..

thanks again

mark

[mark-mk3gti]

if the car runs the immob box can communicate with the ecu ok, unless you mean it fires up for a couple seconds then cuts out? thats immob fault symptom. if car runs for a whiel and cuts out at junctions then its nothing to do with the immob.

if you look above the fusebox near the column you'll hopefully spot the immob box. its black and a little smaller than a pack of cigarettes. its well hidden in a mk3 dash, proper mare to get to! follow the wire from the transponder ring and hopefully you'll spot it. then there are 2 grey or grey/white wires, 1 runs to the diagnostics jumper block above the fusebox the other connects to the ecu diagnostics wire with a brown plug

hi mate, i never really did anything bout this issue, but was a bit bored for an hour so went to have a look, car runs perfectly after crank sensor (touch wood no ive prob cursed it) and bein looking into vagcom fault again, still cant read ecu and as it turns out the immob, but can always read abs module, so does this point to immob box fault? 



i havent pulled it all apart but have had a look and have seen the box on fusebox and can see immob box no prob, only thing i havent seen is that brown plug, have checked grey/white wire is present at diag socket, and there are a few in this rail thing on fb, that brown plug, from what you said it runs onto ecu? if it was d/c would car run ok? but diags not connect?

there is no mad rush to get things going but i may need diags one day..

what would u do?   guess i need to locate that brown plug and check it is connected ok? or am i gonna need to pick up a immob box with a key?

cheers for your help..

[rubjonny]

aha. see that wire on the far right? move it to the top row. its on the bottom row, which is the wrong place. see all the other grey & grey/white wires are on the top row?

top row and bottom row are separate circuits

[mark-mk3gti]

just gonna try now, brb,  maybe thats why it didnt always connect? when i first got the car, and dare i ask why the hell is it in the wrong place, lol   brb

[mark-mk3gti]

hi mate, just in car now and still no joy, it doesnt connect with handheld thing, and laptop with 409.1 or lite, so am i back to the plug? it was never gonna be that easy for me, lol,

btw still get abs ok on both...

[rubjonny]

follow all those grey wires to where they come from, one of them should run to the immob box. check out all the other connections there and see if anything looks odd. if nothing runs to the immob box, follow the wires from it till you find the grey wire which should be connected to the jumper block and plug it in!

if it all looks ok then i would say the issue is the immob box itself. see if you can get a random one from scrappy, plug that one in and retry the diagnostics

[mark-mk3gti]

hi mate, ok ill have a go at some point very soon, just it bloody freezing, and cant feel my fingers again, dunno if it makes any difference but when trying to connect to immob or ecu you can hear the clicking sound from; i assume the immob box, but then it fails to connect, its an absolute jungle behind the fuse box, so will take me a while i reckon, so will have to do it on my next days off, cos i need it to get to and from work, so cant start out today,

you obviously know ur way around electrics in these things, shame you arent a bit nearer the manchester area
but why would it of worked at all with that wire in wrong place? it makes sense they shud be on the same row,

ill keep my ears and eyes open for an immob box and test that see what happens, in theory would all the diags then work even with the immob box not coded correctly? just read a previous post!

[rubjonny]

that does suggest wire from there t oimmob box was fine, and that other wire was for something else.

sicne car runs, and immob box clicks i would say the wiring is ok, but the immob box is bust. assuming ecu is post-96 one with built in immobiliser anyway, if early one or immob has been bypassed then there doesnt need to be a diagnostics line between ecu and immob box for car to run

[mark-mk3gti]

hi mate, sorry im taking up ur time with this, ive got it in my head again, and would like to get sorted, so should i put that wire back?

car is a 96, registered in oct, but that doesnt help,  how can i check which one i got?  and what would u do next?  have to say im getting confused again lol,i was just starting to get to grips then boom, lol

i went out and had another poke around, think i found most of the connectors and wires, but hard to trace as go into a loom, but think ive seen most of them now, and all look to ok, obviously im not 100% but am prob close...

i'm guessing (correct if wrong)  that of my four plugs, 1 goes to diag port, 1 to abs module 1 to ecu module   srs  and 1 to immob, im pretty confident that brown one u had me move goes to immob, but hasnt changed anything,.    and then a grey lead from immob to ecu via brown plug,

so maybe i should get a uncoded key cut and see if car runs without chip, if it does then either immob is knackered or being bypassed, but if cuts out after is it like 10secs? then immob ok?

so shud i get hold of another box and swap test see if diags come on?
initially when i got car, it did work, but took a few goes and was hit and miss, so thinking bout it could be the box,

what would you try?

i am really sorry! are you going to pod in april? need to get you a beer!!