Golf 2.0 AGG Can't communicate with engine ECU

Hi
Wondering if anyone could help me with this Golf.


VCDS Version: Release 12.12.2
Data version: 20140212
Specialist Motor Service
Monday,07,April,2014,16:05:13:49214

Chassis Type: 1H - VW Golf/Vento III (1992 > 1999)
Scan: 01 02 03 08 12 15 25 41 56

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Address 03: ABS Brakes Labels: 3A0-907-379.lbl
Part No: 3A0 907 379 D
Component: ABS ITTAE 20 GI V00
Coding: 03704
Shop #: WSC 00000
VCID: 2B5EFBB2D9C50E461E5-4A52

1 Fault Found:
01276 - ABS Hydraulic Pump (V64)
16-10 - Signal Outside Specifications - Intermittent

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Address 15: Airbags Labels: 1J0-909-60x-VW3.lbl
Part No: 1J0 909 608 K
Component: AIRBAG VW3 S V04
Coding: 00075
Shop #: WSC 00000
VCID: 3668DAC6128743AE71B-4B00

No fault code found.

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Address 25: Immobilizer Labels: 1H0-953-257.lbl
Part No: 1H0 953 257 B
Component: IMMO VWZ3Z0M2519376 V00
Coding: 09600
Shop #: WSC 35110
VCID: 2A50FEB6D63F174EE53-4AE6

1 Fault Found:
00546 - Data wiring faulty
27-00 - Implausible Signal

End ---------------------------------------------------------------------

Keep getting 00546 DTC. Vehicle has been fitted with new engine ECU and immobilizer ECU. Local VW workshop coded and even they got the same code but claimed that the VW system confirmed that coding had been successful. Strangely they charged me for coding both the engine and immobilizer ECU's individually, how they achieved that without being able to communicate with the engine ecu I'm not quite sure. The engine starts and cuts out almost immediatley. Signal from immobilizer to engine ecu remains constant. I have checked all wiring and signals between the 2 ecu's and found no fault. Fuel and engine control relays have been substituted for known good units with no change in behaviour.

Any ideas would be gratefully received.

Chances are the 0x01 engine ecu K line is damaged or unplugged at the TV ALDL junction above fuse panel to ecu or plugged into wrong TV.

This is also why the 0x25 Immo is reporting an error on the BUS.

Trace out per wire diagrams or send me the engine ecu for Immobilizer defeat service we offer here.
www.fixmyeuro.com

Yeah, the ECU communicates THROUGH the immobilizer, and the fact that the Immobilizer has this fault:

00546 - Data wiring faulty
27-00 - Implausible Signal

... makes me think there's a wiring issue.

-Uwe-

Yeah.......its only one wire if you want to run an overlay back to the ALDL or BUS TV under dash and or isolate.


I would unplug all systems at ALDL BUS TV and fire one up at a time for COM especially isolate ABS first and foremost.
The fault present in ABS 0x03 on network may stop com with engine.

Hi Thanks for replies
I think I should give little more history of the fault as I have checked the points suggested and everything seems to check out.

The car arrived as a non-starter. Customer had been driving car, parked for 10 mins, came to restart and engine refused to start at all. They towed the car to our shop. When the ignition was turned on everything on the engine was playing a tune. The injectors were operating randomly, the throttle was motoring away merrily. Attempting to start engine revealed engine was locked solid, full with fuel (ignition had been left on during tow). Quick check with VCDS revealed 00546 DTC. Due to the fact we were busy and the number of issues all happening at once with the engine electrics I committed the 8th deadly sin and decided without further testing to pull the ECU and send it for testing.

The postal service kindly lost the ECU, so a new unit was installed. Still no start. Saw that the K-line was routed through immobilizer so decided to fit new immo ECU as well even though signals appeared to be correct. Off to main dealers for coding, still no start, back to shop. A sensor check showed up a strange signal from the crank sensor which I replaced. Bingo, engine started and promptly died.

Check with VCDS in the immobilizer revealed engine ECU was responding to the immo ECU. That brings us up to the point when I decided to seek advice.

The ABS fault code was not present when testing started, kicks in when batt voltage gets a bit low. As ERWIN refuses to give me a vehicle specific wiring diagram for this car I am still trawling through hundreds of drawings trying to find info on the fuse box connections. I am not quite sure if the small connector block with 4 wires attached on top of the fuse box is the ALDL bus that Jack referred to but everything seems good there as far as I can see. Continuity checks on all the wires (plugs disconnected) between Diag plug, immo ecu and engine ecu reveal no faults.

Apologies for the epic, this one is driving me crazy.

Silly question, but is the ECU getting power (both switched and unswitched) everywhere it should? And have you checked the grounds?

-Uwe-

I thought the same thing Uwe but he said it started and died.

My question is............. even though you can't communicate does the MIL/check engine illuminate on dash when key is on?
Also in A3 1H series cars......... if the airbag controller is not grounded....... like literally to the body to controller bolted down .......... this can also disrupt the K line for engine in my experience.

Please advise.

Power and grounds all present. I also setup the scope on the ecu to see if it was signal disappearing causing problem, everything, including the signal from the immobiliser ecu remains constant when the engine shuts down.

The Mil lamp is a mystery, I can't find one. The information I have makes no mention of it either. It occurred to me today that I have never seen one. More investigation on that one in the morning.

It is possible based on your region it might not have one but usually they do.....
All A3 1H series cars here in the USA do have an MIL from my experience with at least rapid data transfer 92.5>

Jack@European_Parts said:

I thought the same thing Uwe but he said it started and died.

Click to expand...

That doesn't mean power or ground aren't wonky.

Bottom line here is it looks like both the immo and VCDS can't talk to the ECU. One interesting test might be to pull the immo module out, jumper K to W. The car will not run in that condition, but it would be interesting to see if the ECU then talks (and what faults it might have).

-Uwe-

That doesn't mean power or ground aren't wonky.

Click to expand...

Agreed..... I would still want to go direct to the ECU for COM at K line....... verify it speaks and than trace back with a tone generator to open or short looking for what's causing the implausibility.

Emulation is also possible to get this car running past the Immobilizer issues.....however, it is recommended to fix the problem.

Checked airbag controller ground, everything good.

No MIL light fitted to this car, according to user manual.

When looking at the immobilizer with VCDS, I see the following.
Engine start permitted=1
Engine (ECU) responds=1
Key status=OK
Number of adapted keys=N/A
To me this suggests that the immo ECU can see and communicate with the engine ECU.

I have run a new wire direct from pin 7 diagnostic plug to pin 43 on the engine ECU and still no response. If I'm understanding things correctly this is the path for the K-line. The new wire was run from contact to contact to isolate any possible short in the original wiring.

This may suggest an engine ECU fault if I had not replaced this unit. The postal service finally found and delivered original unit which has been tested and comes up clean. It must be a million to one, for a new ECU to have exactly the same fault as the old unit.

The only idea I have is that something is wrong in the fuse box and that the new wire I ran to the engine ecu cannot provide the data VCDS requires on it's own. Am I missing? something.

Is the new wire connected while the old one is still present and hooked up?

No, detached original wiring so a possible short couldn't influence test

You try disconnecting the ABS module didn't read that in any post?

I have had ABS knock out communication before. Usually a totally bad ABS does this though.


"I have run a new wire direct from pin 7 diagnostic plug to pin 43 on the engine ECU"
You think that would do it.

"It must be a million to one, for a new ECU to have exactly the same fault as the old unit."
I don't know about you but with my luck it would.

Good Luck

Have you tried a direct wire from ecu K-line direct to your ALDL so only VCDS can speak to isolate?

Yeah I said that to in post 4, not sure if I was observed.....

Sorry missed it in #4

I thought that strange. "first and foremost"

Good Luck

vw tech
Yep, I have disconnected everything that VCDS can talk to without any change but thanks for the input.


Jack

Sorry you have got me a little with the abbreviations. ALDL BUS TV? There are 2 bundles of connectors above the fuse panel on this car. One is a row of connectors with 3 single and 1 double connector in use, this is actually attached to the top of the fuse panel. This panel does have 2 connectors with gr/ws wires connected to it. Are these the guys you are referring to? The VW wiring diagram shows only 1 gr/ws wire terminating at a single connector behind relay plate so far I haven't been able to find that one.

Yes correct that is the TV connector bridge that is referenced in wire diagrams. It is above fuse panel and has the K-lines Grey/White strip typically.....

ALDL = Data link connector for the scanner to plug into ( OBD2 port )

I want you to run a direct wire to K line at ecu............ back to obd2 connector and establish com with ecu directly............ as if it was on bench.
( That should be also Grey/White stripe at ecu )

Yep, that was the test I ran this morning, still no comm! I get battery voltage at the k terminal on the engine ecu which is correct according to the info I have