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

[mark-mk3gti]

hi all, being trying for ages to get vagcom to read ecu, it used to, but now will not, what ever i try i can always read abs module but rarely now not at all the ecu
i purchased a hand scanner which works fine with abs, but says error when connecting to ecu,
i can hear clicks  behind clocks but fails.

bein having the cut out while drive issue for a while and yesterday replaced the crank sensor, which was cream crackered, when i got it out had a look at cable which  looked finebut when messed with it a little bit it fell apart in my hand, dont think it was shorting but definately brittle cables and generally looked crap.

just gonna have a look at ecu and see if i can clean pins up or somet, but anyone got any idea why it would stop reading? is ecu fubared? 

any help apreciated,  btw its a 96 gti 8v 125k agg engine

[AudiA8Quattro]

What version of VAG com are you using? later ones are better.
The ECU could be at fault itself.

[mark-mk3gti]

I've tried all of em, but originally 409.1 worked with eBay lead, but now doesn't, hand scanner is the correct one and can read abs, just cleaning pins on ecu now, but didn't work, so giving it another go and checking loom as best as I can, but yeah doesn't look good for ecu I guess

[rubjonny]

nothign wrong with vag-com if the other scanner cant see ecu either.

look behind fusebox for any grey/white wires, there should be one from ecu to a plug on the immobiliser control unit.  try vag-com again ands see if you can connect to the immobiliser, if not then the unit has packed in. if you can that suggests the problem is the comms between the immob unit and the ecu. it is also possible for the immob boxes to fail in such a way they still power up and communicate with vag-com, but they wont communicate with the ecu. this will lead to immobiliser issues.

the clicking noise you can hear is the immob box, this means the immobiliser box does at least have power, and it can see that you are trying to communicate with the ecu

[mark-mk3gti]

Hi, thanks for help, just tried to connect with immob but no joy, slowed baud rates down in case and still doesn't, but does abs.  Just noticed am running ftdi drivers for port, that ok? I've tried a few.. Lol
Car starts and runs but have being having the cut out problem, crank sensor was knackered so replaced, but now I am wondering if immob box is the prob, is there anyway of removing it so everything works normally? Ie vagcom as car does have another Alarm onnit, can the immob box be changed easily? Guess it needs recoding aswell! Sounds like fun!!

[mark-mk3gti]

Had a look for wires but couldn't spot them, it's a jungle and only had small torch,  think i can see the immob box, is it up to the left of the column? Looks like it's silver with couple of plugs on it?
Think it's gone above my head electronically, am not sure what's best to do now? I'll know if it runs right now after a few work runs as that's when it happens the most, but this vagcom fault code reader thing is bugging me a lot.. I like everything working as it shud, where to go now?

[rubjonny]

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

[mark-mk3gti]

Hi mate, yeah I saw that box! Looks like fun to get out!
Take it u disconnected yours then?
Yeah the prob was revs dropping at speed and on one occassion when at lights, just changed crank sensor as it was knackered and also realised I had cyl 3 n 4 firing wrong way round for several months :embarassed:

Just wanted to read codes off car, if u reckon immob box is causing it is it just a matter of disconnecting it from car?
Sorry if I'm seeming a bit dumb just wanna get it right as this my daily!!

[rubjonny]

nah i put one in, abf swap into mk2 golf

wasnt fun ripping that loom out in one piece from the donor mk3 i can tell you!  you cant just pull the immob box either, to bypass it you have to send the ecu off to have the immob defeated.

as i say, if the immob is the problem you can get one from any other mk3 golfy just as long as it also comes with a matched chip. once you fit the matched box and chip to your car/key, you then use vag-com to code your ecu to them.

to match new keys to the immob box you need the skc code, and you can only get the skc code if there is a matched key in the ignition. i.e. random immob boxes on their own nicked from the scrappy are as good as scrap without the key to match!

[mark-mk3gti]

hi john,

sounds like fun, lol, shame there is no way of proving its the immob box, although i guess i could get one with a key/chip and swap boxes and see if vagcom connects to them both? would that work? would it allow me to connect even if immob not coded to ecu or vica-versa?
 then if it does connect to ecu and immob then i can code everything up.. hopefuly

what would u do?

i just dont understand how i can always connect to abs module first time no problems but nothing else, i wuld of thought abs went through imob aswell as i am sure it clicks the same aswell

hopefully crank sensor solves my problems with rpm drops, will no over weekend after work runs..