MK1 Gti to ABF wiring fault, fires but doesn't run one for rubjonny

Hi All,

Please help with this I am at my wits end trying to figure this out, I really need some pointers ideally from rubjonny
Many moons ago I followed this thread https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=modifications-and_2%2Fdx-to-abf-conversion to convert my wiring to run the ABF on its standard management using the CE1 fuse box.
All was well and this worked perfectly. A couple of months ago I had to remove the fuse box. I thought I labelled everything up correctly but in my heart of hearts feared the damn thing would probably never run again. My fears were correct, after refitting the car fires up and runs for a few seconds before dying. I suspect the immobiliser. Also I noted the fuel pump is not running so I bridged the relay but this made no difference to the firing then cutting out. I have vagcom and the port wired in but this no longer works since the fuse box came out,  vagcom refuses to connect, I can try again and get the exact message if required.
I have gone back through the above thread and checked all wiring to the ecu everything seems correct. It should also be noted that with the vagcom lead plugged in the led on the lead flashes quickly for a few seconds when the ignition is turned on, but then goes out. I seem to remember it stayed on before but could be wrong.
I could use some help with this as my Golf is just sitting in the garage when it should be being driven. Thank you in advance Chris

Someone must be able to help me out, make a suggestion, compare what their OBD cable does. Give us a clue please.

Anyone?

ok for starters chase back your vagcom port wiring. if it has an immobiliser it will be between the port and the ecu diagnostics wiring. the box needs ignition live on the black, earth on the brown then 2 wires for diagnostics so its not complicated. if you listen carefully to the box it should click ignition on.

try to connect to the immobiliser box as well, address 25. sometimes the internal changeover fails preventing you from talking to the ecu through it

does the isv vibrate ignition on?

Thank you very much for the reply. Immobiliser box fitted. 12v switched present on the black wire, brown to ground measured at the multiplug going in to the immob box. No click heard from box. ISV heard and felt at ignition on.

What the fudge? I just started it and it ran. I have made no changes other than I noticed that the brown (ground) cable running from the diagnostics port to the immobiliser box has an area without any sleeving on the cable, this appears to be factory. I connected a cable between this and an earth point and the led on the diagnostic cable lit up. Then I tried the car and it started?????????????

the immobiliser and vagcom port earths are seperate, so if they're joined this suggests someone has modified the wiring. the bare area may have had an earth wrapped round it by whoever made the loom which got pulled off when you stripped it all back?

but whatever, works now

I made the loom ages ago. I think I have figured out the issue.
Am I correct in saying the immob box has 2 grounds? If so one of those has popped off when I took the dash out.
 

sofarsogood said

I made the loom ages ago. I think I have figured out the issue.
Am I correct in saying the immob box has 2 grounds? If so one of those has popped off when I took the dash out.
 

Why not get rid of the immobiliser get it running then readdress the problem once it starts and runs ?

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nicci21paul said

sofarsogood said

I made the loom ages ago. I think I have figured out the issue.
Am I correct in saying the immob box has 2 grounds? If so one of those has popped off when I took the dash out.
 

Why not get rid of the immobiliser get it running then readdress the problem once it starts and runs ?

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I run a mk2 abf no problem with out any obd a basic ecu running fine no idle issues without isv

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yes immo box has 2 earths which run to an ultrasonic welded joint then a chunky wire off to a ring terminal which earths to shell.

immo removal is another way round it of course, but why spend the money having it done if you can just wire in the immo box. can even fit reader coil somewhere accessible and have it work as VW intended, help stop your car getting pinched  or very basic way just remove key from reader when you park it.

you only need to wave chip at coil while you're starting it, once fired you can move it away

rubjonny said

yes immo box has 2 earths which run to an ultrasonic welded joint then a chunky wire off to a ring terminal which earths to shell.

immo removal is another way round it of course, but why spend the money having it done if you can just wire in the immo box. can even fit reader coil somewhere accessible and have it work as VW intended, help stop your car getting pinched  or very basic way just remove key from reader when you park it.

you only need to wave chip at coil while you're starting it, once fired you can move it away

I agree with you 100% but if you take the immobiliser out of the equation the car starts and runs then back track to the problem does that make sense

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true, but the problem in this case WAS the immobiliser

yes immo box has 2 earths which run to an ultrasonic welded joint then a chunky wire off to a ring terminal which earths to shell.

It was one of these that had popped off. As it happens I was also using this chunky wire as the earth for the diagnostics.

Thank you rubjonny