el_wacunio
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« on: April 09, 2025, 09:33:58 AM »
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Hi everyone,
as mentioned it the title, I'm fighting with my TT which had a AUQ ECU, which was wideband but now I swapped it with a AJQ one which is narrowband, but the car is in some kind of a limp mode which can be "disabled" by pulling out fuse 11 which delivers power to the cluster or the cluster itself (I can start the car because ECU has immo off). When there's no cluster the car feels and runs at it should, but when it is connected, ECU cuts down the power giving me only 0.3-0.4 bar of boost pressure (1350 mbar absolute) when the requested value is normal at 1750 mbar, also MAF reading are low (max 80 g/s), I checked 3 different N75 valves, 3 different MAF sensors, deleted N249, changed the cluster, no leaks in the system. I'm out of ideas, there are no DTC's in VCDS, any help much appreciated!
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_nameless
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« Reply #1 on: April 09, 2025, 04:28:09 PM »
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Hi everyone,
as mentioned it the title, I'm fighting with my TT which had a AUQ ECU, which was wideband but now I swapped it with a AJQ one which is narrowband, but the car is in some kind of a limp mode which can be "disabled" by pulling out fuse 11 which delivers power to the cluster or the cluster itself (I can start the car because ECU has immo off). When there's no cluster the car feels and runs at it should, but when it is connected, ECU cuts down the power giving me only 0.3-0.4 bar of boost pressure (1350 mbar absolute) when the requested value is normal at 1750 mbar, also MAF reading are low (max 80 g/s), I checked 3 different N75 valves, 3 different MAF sensors, deleted N249, changed the cluster, no leaks in the system. I'm out of ideas, there are no DTC's in VCDS, any help much appreciated!
Post data logs if you want help |
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If you are broke or expecting free handouts DO NOT message me. I'll probably put you on blast if you do.
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el_wacunio
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« Reply #2 on: April 09, 2025, 11:56:10 PM »
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Hope this one helps, I know it isn't perfect, but it shows the problem with achieved boost pressure, also I've checked voltages on N75 plug, not by measuring between both pins of the plug, but every pin separately and the results are as followed:
ignition ON, fuse 11 in, pin 1 - 3.5V
ignition ON, fuse 11 in, pin 2- 0V
car ON, fuse 11 in, pin 1 -3.5V
car ON, fuse 11 in, pin 2- 14.3V (Alternator voltage)
ignition ON, fuse 11 out, pin 1 - 3.5V
ignition ON, fuse 11 out, pin 2- 0V
car ON, fuse 11 out, pin 1 -3.5V
car ON, fuse 11 out, pin 2- 11.9V (probable reason of the boost difference)
Also what I checked was the N249 valve (I have bypassed it but if left the solenoid itself) and when fuse 11 is in and the ignition only is on i the plug I can observe some voltage, not much, around 3V, but when the plug is out and the ignition only is on, both N249 pins shows 0V. So what I can see is that the ECU signal to both valves might be good, but the power voltage that goes from the battery terminal via fuse 34 is different depending on the fact of fuse 11 or cluster being in.
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fknbrkn
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mk4 1.8T AUM
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« Reply #3 on: April 10, 2025, 02:00:14 AM »
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whats the point of changing ecu to narrowband?
voltage difference youve had because of alternator needs initial current from cluster, you can rev it to 3000 to achieve that without cluster
anyway this stable pressure of 1350 could be the result of
diverter valve issue (just plug it directly to manifold)
n75 issue, only oscilloscope could help here on connector with plugged in n75
who knows the 'magic' youve done with this swap. ive seen once coolant line plugged instead of evap and theyre tryna to find why it smokes like sht
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el_wacunio
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« Reply #4 on: April 10, 2025, 02:17:02 AM »
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I did the ECU swap because my o2 sensor was not working at all, because someone who put AUQ ECU into the car before probably didn't make any modification to the harness. I've recently changed the DV and also it is already plugged directly to the manifold because I've bypassed N249. But I can't think of a mechanical problem, because why would the car drive much better when the cluster is out? And for the N75 I don't own an oscilloscope but I've ordered an MBC to test if that's causing the issue.
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fknbrkn
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mk4 1.8T AUM
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« Reply #5 on: April 10, 2025, 03:18:24 AM »
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I did the ECU swap because my o2 sensor was not working at all, because someone who put AUQ ECU into the car before probably didn't make any modification to the harness. I've recently changed the DV and also it is already plugged directly to the manifold because I've bypassed N249. But I can't think of a mechanical problem, because why would the car drive much better when the cluster is out? And for the N75 I don't own an oscilloscope but I've ordered an MBC to test if that's causing the issue.
Ecu request 1750 and get 1350 which is a spring pressure Log wgdc (114), if it's constant 5% then it's a some kind of overboost event or so, ecu probably modified with dtc mask out or so.. If it's nearly 95% then a hw issue |
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el_wacunio
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« Reply #6 on: April 10, 2025, 03:26:09 AM »
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Okay, I'll make some more logs and give you feedback, but can you please tell what what hw means? Hardware issue? I'm also quite confident that the ECU map is stock, only IMMO OFF. And about the spring pressure, you mean spring pressure in DV? Can the DV even if it's new cause that?
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el_wacunio
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« Reply #7 on: April 10, 2025, 07:17:30 AM »
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Big update! Thanks to @CragyBar on UK's audi TT forum I thought to check the ABS pump again, so this time I've only pulled the ABS/ESP fuse (number 9) and it worked! Now the car drives like without the cluster, sadly MAF is still low, but I've send back the new OE part and putted in the old one seeing that the new one didn't help. But maybe after I'll repair that ABS module MAF will work too, we'll see. Anyways, now the turbine builds up normal pressure up to 1760 mbar, the engine load hits up to 112% and MAF readings at peak value shows 103, but that's maybe still be caused by the fact that there's no connection to ABS from ECU. Also I'll attach new logs that I've made and maybe somebody could say what could be the cause to still low MAF? Anyways thanks to everyone for the help so far and I'll keep you posted  |
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el_wacunio
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« Reply #8 on: April 11, 2025, 07:10:37 AM »
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Alright, another update, it is the ABS fault, but not because it is faulty, it is probably caused by ESP. I have a APP engine and ABS with ESP on board and as you know I'm using AJQ ECU which probably wasn't equipped with an ABS with ESP in it. I'm saying that becaue on my other AJQ TT with AJQ and everything else stock the ABS pump has another soft coding. Also as soon as I push the ESP button in the car, the power is back, but the MAF is still super low. Is there a chance, that someone could provide me with a ECU file which has ESP and IMMO codded out and is completelly stock otherwise? I didn't do any mods on the car, just unplugged the post-car o2 sensor and SAI pump because the're not used.
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