Hi all,

I've got an odd misfire on my Golf, so picked up a lead to try and scan it after a VAG indy failed. I got one of these: http://www.gendan.co.uk/product_VAGUSB.html which works fine on my Polo running the free VCDS. It also works fine on the Golf, except on the engine module (typical, 'ey?).

I get an unknown protocol, 9c9c error, or words to that affect. Reading around, it could be the aftermarket radio, so I pulled the fuse, which took all power away for the radio. The issue still persists. Can still scan other modules fine after it doing this, and it reads the engine module on the Polo without issues.

Anyone able to shed any light?

It might be worth also noting that the car sometimes fails to read at all, and give an error saying that the interface could be down, and suggests checking ignition, connections etc (which are all ok), or that the 'K Line has locked up', whatever that means! I'm guessing is what the VAG garage caught it doing somehow.

Thanks,

Joe

Right, nothing annoys me more on forums than when a thread trails off to nothing without an answer so here goes:

I got no reading (9c9c protocol error) on VCDS. A garage got the same thing (different error, but still no connection). Said garage have:

1. tested all wiring for continunuity
   
2. swapped the dashpod for a another off a another Golf
   

Nothing happened, concluded dead ECU. Picked one up off of eBay, coded immobiliser to the ECU (made the car run much better although still dog slow for 150bhp!), but still no reading. Garage then checked the wiring again, and found a short somewhere along the line. Replaced this length of wire, still no connections. Check all the wiring again (don't think any faults were found).

Tried removing other items such as the ABS which use the same system/comms line as the engine ECU - still no joy. When I last left it, they were planning to do some more checks on the wiring, but frankly, unless I've another duff ECU then I can't see anything else that's left!

If anyone else has any ideas then great! But if not I'll update this again if/when we reach a definitive answer.

Joe

Any help:

http://forums.tdiclub.com/showthread.php?t=50665

Have you disconnected the K-line from the radio?

RE that club TDI thread - I saw that a while ago I think. The first garage used 'proper' VCDS lead/software. I've tried a cheap Gendan lead and VCDS-lite and the same lead on a friends full version of VAGCOM 409.1. All wiring has been checked too, so I assume it's not that.

I removed the fuse from the radio as it was easier to get too. Same affect I assume? I mentioned it to the garage and they said they were aware of the potential issues.

Anyway, an update: The garage has admitted defeat. :( Combination of lack of remaining ideas, but mostly time. Gonna go bug the Golf forums for a bit with my woes, and we've a friend of a friend type person who specialises in VAG electronics so will see if they can help.

What I'd love to try is to put my ECU into another car/Golf and see if it yields anything. I might try this over the weekend when the Golf is in my hands.

Thanks,

Joe

...I removed the fuse from the radio as it was easier to get too. Same affect I assume?...

No - not always. It depends on the head unit.

By removing the fuse you prevent voltage clamping the K-line high, but the K-line is still connected to the head unit. In some cases the internals of the head unit distort/degrade/attenuate the K-line signals.

Hmm, I'll give removing it a go then, although the same HU was in the Polo and that never suffered the same faults so might be a red herring.

Thanks

That error is always a pain to track down. IIRC, it's caused by a timing error. It can be caused by the computer, lead, an A76 fault (K-line wiring), one of the items connected to it or bad power. Sometimes you can connect with ignition on but not when the car is running.

Do a port test in VCDS-Lite and post the result. That often gives some clues.

I usually use a breakout lead or bench lead to connect direct to the ECU.

Well it's been used on 3 computers and 3 leads (one was one of these 'several make' things snap-on etc make for garages). They say they've checked all the wiring and it's all good (but I'll confirm for myself on the weekend). Before it went away I could get into other modules, just not the ECU and ignition position made no difference.

I tried to do a port test and set the dash pod to UK from US, and it kept giving an 'interface status = -1' (suggests interface not powered, connected, or busy k-line) error. It's done this before and I've solved it by going to the Polo, testing the port in that car and going back to the Golf with the settings in mind from the Polo. That's not been working this time, so I can't get into anything atm.

I'll try disconnecting the battery in the morning, see if I can get the k-line to reset. If I can get it to work, I'll post a port test test output up.

Are you able to expand on the breakout lead/ bench lead status? Guessing it goes directly to the ECU from a laptop or something?

Problem is I ideally need to log real time data to see if it's not injecting fuel, or down on boost which I guess I can't do if it's connected with a bench lead?

Thanks for your help/patience!

Joe

Edited 30 March, 201214 yr by TriggerFish

A 'bench lead' plugs directly into the ECU and has only the connections required to talk to the ECU. Whilst it does confirm the ECU is OK, having no sensors connected, throws loads of errors.

A 'breakout lead' is a plug/socket that goes between the ECU/loom (like a tuning box) and passes all signals apart from the ones you want to investigate - in this case diagnostics.

TESTING CABLES WITH A MULTIMETER ON RESISTANCE WILL FIND BREAKS/SHORTS BUT DOES NOT CONFIRM THE WIRES/CONNECTORS ARE GOOD. Water ingress/corrosion causes capacitance on the wire and degrades the signal. Check for water ingress in the plenum chamber connection box as this seems to be a common cause of problems on older VAG cars.

What engine/year is it?

Right, thanks.

He said he's also run 'tracer' wires too, to replace the diagnostic ones but in place by VW so I assume this would get rid of any signal degradation etc (he couldn't remember if he'd left the VW ones attached, or disconnected them though). I've not yet checked these as I literally got the car back and went to the pub. Figured I'd look tomorrow when I have all day and don't have to worry about it getting dark 1/2 way through.

Will have a look at the plenum connections tomorrow, see how they're looking.

It's a 2002/mk4 Golf, 1.9 TDi PD (ARL coded - 150 if that makes a difference).

I've had a read of my notes

It's the 10-pin orange connector in the plenum chamber connection box.

Check continuity of grey/white wire from diagnostic socket (pin 7) to blue plug on dash (pin 25).

Check continuity of grey/white wire from green plug on dash (pin 5) to ECU (pin 19).

If both OK, unplug both dash plugs and connect blue plug pin 25 to green plug pin 5 and see if it works. If it works, there is problem with the dash insert.

HTH

Right, an update.

I disconnected the battery, checked all the plugs etc, plugged it back in to check that it wasn't working (so I knew if my work was getting me anywhere) and it worked!

I stopped, had lunch, waited for my dad to be free so we could log some data, drove to a safe bit of road, and it didn't work! Tried the same things I did earlier (remove battery, poke at connections) and nothing again.

What this has at least proved to me is that the ECU is good, and the wiring seems OK (I know it could be a lose connection that moving the car distrubed). What is unknown still is weather it's an intermittant problem with the dashpod, or the wiring.

I'll go in a bit once I've calmed down and try the pin 25 & 5 idea, see if that gets me anywhere.

OK, been out and tried bridging those two wires as suggested, which it looks like the garage had tried already as they are partially stripped mid wire.

Did this, went into VAGCOM and got an interface =-2 error on all modules. Removed the bridge and most modules were working again, all except the ECU!

Is this pointing towards being a duff cluster? (Although the garage had a Golf they were stripping, and have tried swapping clusters already.)

Edit - the radio is now out too and sitting in the footwell, so it's not that that's doing it.

Edited 1 April, 201214 yr by TriggerFish

OK, you have eliminated the cluster. Sometimes they fail to forward K-line signals to the ECU.

Can you see the dash in VCDS?

As you have already swapped the ECU, you are left with...

grey/white wire from green plug on dash (pin 5) to orange plenum connection box connector.

grey/white wire from orange plenum connection box connector to ECU (pin 19).

I could see the dash, yes.

I'll have another look at the weekend, as I need the car for commuting.

Thanks for your help.

Edited 3 April, 201214 yr by TriggerFish

I could see the dash, yes...

Good. That means the problem is definately between the dash and ECU

Just to confirm, you do mean this connector right?

Between the two prongs for the wiper setup? Connecting onto the ECU.

Edited 10 April, 201214 yr by TriggerFish

No, it's under the wiper motor. There is a box about 125mm square. If you remove the lid there are about 6/7 coloured connectors that lead to the inside of the car. You will have to remove the wiper motor to get to it.

Thanks

Will go and try once it's stopped raining (again!).

can you see every other module on the car with vcds? do they all show a no communication fault with the engine ecu?

sometimes the airbag controller can get a bit wet and this will kill comms to random modules, or keep unplugging things until it talks if the wiring to the ecu checks out ok (I suspect it will).

I could see other modules - we tried unplugging other modules too. Thanks for the thought though!.

Just to finalise this, I'd never been happy with the car, and was seriously considering getting rid of it. It was recently crashed into (not my fault) and although it only did a little damage it was the final nail in its coffin, so it's gone now.

Never did get to the bottom of it - the ideas tried above, a month in a garage and few hours in the hand of a VAG specialist and it's still broken.

It's put me off VAG for a while though, so looking at 3 series now.

Thanks for everyone's help though!