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1.8t I think I've killed it!

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OBD port not connecting & it won't start

So I have a nice 1.8t which I got as 90% finished project. Runs ok with MAF disconnected but rough when connect.
But before sorting this problem the ECU port is dead and does not connect to OBD reader. So have to sort this.
Checked all fuses on the Mk1 fuse box only No. 1 gone, so replaced with a new 20 amp fuse. But no change to ECU port reader.
Checked voltage across pin 4. Ground and 7. K-line. It gave a reading on 11.6V.  Car was still running ok.
Then checked voltage across pin 16. to -ground point under dash & pin 13. to ground under dash. No voltage on meter.

Big problem now the car won't start. Turns over but won't fire up. Mk1 fuse box fuses are all ok. So what have I broke.

Is there other fuses some where that I have missed that I need to check or a relay?
Any ideas on what could be the problem. Could I have Killed the ECU.

What should I check?
 

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Does your fuel pump prime?

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I can't remember hearing it but will double check to confirm. There was a smell of fuel when turning it over. What were you thinking andydlc?

I suspect it is fuel, spark, fuse or ECU issues. 
But where to start. 

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pin 4, 7 and 16 are all you need for diagnostics. 16 has no power so thats prob why its not reading codes. factory mk2/3 its fed to ciggy lighter power, so check that. failing that chase wire to source to see where its fed from.

recheck the fuses, use a multimeter they can get hairline crack which is hard to spot. top suspects would be 17 and 18 often used to trigger ecu relays and such on conversion looms, plus 5 which is fuel pump power assuming factory fuel relay socket was used.

apart from that its hard to diagnose remotely as it woudl depend on how the loom was made, soem use fusebox feed direct to power ecu and coils, some use a relay etc. what ecu is it dbw or dbc?

Hello my name is John and I'm a dub addict.



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Thanks for tips rubjonny
Hope I can get some time to look after work. 
Can I identify DBW or DBC from sticker on ecu or does relate more to wiring loom.?

Cheers

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dbw and dbc most easily identified by the throttle body, if it has a cable on it or not, but there are many ecu codes of each so if in doubt just post the ecu part number then we can confirm exactly what engine code it is :)


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So checked the fuses with a meter all fine, bar No11 which was intermittent so pop new one in.
The fuel does seem to prime ok.  Hopefully that's scratch of the list.

The code on the ECU is 06A 906 032 DE & engine is AUQ. The throttle body has no cable and air intake from n/s of car.

So next job is to trace pin 16 to find out why is dead and check for spark.

 

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ok cool so yes DBW AUQ.

now factory these have an ecu + coil power relay in a box in the engine bay, need to find out what happened to that.

also with the DBW looms they are prone to the injector harness cracking up and shorting out, ideally you want to put a fuse on the ecu relay power side when converting the loom for this reason. if there wasnt one the coil/ecu power feed might be burnt out.

what fuel relay has it got while we're looking? if its been wired to use factory pump socket it should be 67, 80, 167 or 409 in slot 2

on the ecu side, these are the important pins to check:
3 - ignition live (so not fed from ecu relay!)
21 - ecu relay trigger (may or may not still be in use)
43 - diagnostics
62 - permanent live
65 - fuel relay trigger (probably ok if pump primes)
121 - ecu/coilpack relay power

Last edit: by rubjonny


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That's great info rubjonny thanks for the help. 

There is a small black box hanging above the mk1 fuse box ( about 70mmX50mmX25mm) if I remember correct with two cable heading back up to glovebox where Ecu is. Could this be the coil power relay?

Hoping to get a little time later in the week to looking in to other possible issues later in the week. Will up date with any findings. 

Cheers. 

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probably, get some pics :)

Hello my name is John and I'm a dub addict.



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So got chance to have a quick look at the car last night. Tried the ignition to test the replace fuse strangely the fuel pump was dead. Tried again still dead. One last go for luck and the pump primed and engine started. So looks like I have a pump relay, pump or wiring issues. 
As to your question rubjonny which pump relay? It currently has a No. 2 relay in position 2.  Is it best to replace with another No. 2 relay or is there an advantage in going for one of the later ones you listed. 
I couldn't get a picture of the boxes ( suspected coil power) but did not it had a red lead and small purple lead coming from it. 
Hope to get the dash removed a little when tracing the OBD PORT live so will be able to get a better look then. 

Cheers

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right so #2 relay is a kjet one, which is triggered by rev counter signal rather than the ecu so the fact it primes or no doesnt tell you anything about the ecu side.

the 67/80/167 is recommended becasue then the ecu has full control over the fuel pump as per oem, but you need to have the ecu relay trigger wire tapped to d/13 on the fusebox for these to work. woudl need to confirm with your loom builder if they have done this

if the relay you found had a thin purple wire then thats most likely the ecu/coil power relay, the fat red is probably the live input look for a fuse on that somewhere it may have popped.

Hello my name is John and I'm a dub addict.



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