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Discussion Starter · #1 · (Edited)
Just installed a Euro Customs Stage 2 tune on my 2001 Jetta 1.8t 5spd. Went for a test drive, stuttering from 2-4k and backfiring when shifting above 2.5/3k. CEL popped so i went to AutoZone and got it read. Main code came back as P0103 with 2 secondary codes being P0343 and P0237. Realized I failed to put washers in my DV as instructed for the higher boost, so I went home did that. Unplugged my battery attempting to clear the code (didn't work) and went for another test drive about 7/8 miles and came back. The stuttering and backfiring was still happening. And now my car will sometimes start and sometimes not. Unplugging the MAF didn't really help with it not starting. I have yet to test drive my car with the MAF unplugged as I don't know if it is wise to do so. Also the ASR/TC light will sometimes pop on and sometimes not. My car has a RKX Precision DV (Not hybrid or any going to the atmosphere), and a K&N cone filter. Any help? All i can think to do is get some MAF cleaner


EDIT: I will be going to a local euro shop to get them to read my car with VCDS and most likely a smoke test to rule out any air leaks.
 

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1999 Golf GTI 2.slow, 2001 Golf GTI 1.8t
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Lol I had one of those valves, until a smog check station dinged me for it because I forgot to take it off.

Did you make sure to install it opposite of how the oem valve is installed?
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Those codes point towards an issue with your sensor ground (GND 220), which is provided by the ECM through pin T121/108. All those sensors share that ground. Check your ECM connector for corrosion.

Is the tuned ECM a new box that you had to install, or is it your original ECM that was flashed? What's the engine code stamped on your head?
 

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Discussion Starter · #3 · (Edited)
Lol I had one of those valves, until a smog check station dinged me for it because I forgot to take it off.

Did you make sure to install it opposite of how the oem valve is installed?
View attachment 183525

Those codes point towards an issue with your sensor ground (GND 220), which is provided by the ECM through pin T121/108. All those sensors share that ground. Check your ECM connector for corrosion.

Is the tuned ECM a new box that you had to install, or is it your original ECM that was flashed? What's the engine code stamped on your head?
From top to bottom. Yes it is installed as that picture shows. The tuned ECM is a new box not the original box. My engine code is AWW and the tune is for AWP/AWW

I edited my post above saying my course of action at the moment
 

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1999 Golf GTI 2.slow, 2001 Golf GTI 1.8t
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Pop your old ECM back in. If the codes go away, then there's a grounding issue on the new ECM. I'm like fairly sure you're got some kind of electrical gremlins on your sensor ground.
 

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Discussion Starter · #5 ·
Pop your old ECM back in. If the codes go away, then there's a grounding issue on the new ECM. I'm like fairly sure you're got some kind of electrical gremlins on your sensor ground.
Just did that today, as soon as it was popped back in no issues what so ever. Perfect drivability. Youre certain is some issue with the ECU and not a stuck injector or anything? I feel like my car is running rich with the stock ecu
 

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Discussion Starter · #6 ·
Just did that today, as soon as it was popped back in no issues what so ever. Perfect drivability. Youre certain is some issue with the ECU and not a stuck injector or anything? I feel like my car is running rich with the stock ecu
I mean I'm not expert by any means but those sparkplugs wouldnt be that dark by driving 15 miles with that tune right?
 

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I mean if you look at the wiring diagram, all the sensors which the codes point to are on the same ground internal ECM ground. And when you put the old ECM back, everything goes back to normal.

What are your long term fuel trims with the stock ECM? If it's running rich on the stock ECM, you probably have a vacuum leak somewhere which the mkiv 1.8t is notorious for. Fix your vacuum leaks before you tune.

If you can return the tuned ECM, I would just send it back and tell them to send you a new one.

It's probably a cracked solder joint for the connector or bad inductor which separates the car ground and sensor ground inside the tuned ECM. If you open it, you probably void whatever warranty they promised (if any).

Edit: also those connectors look fine. Nothing out of the ordinary as far as I can tell
 

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Discussion Starter · #9 ·
I mean if you look at the wiring diagram, all the sensors which the codes point to are on the same ground internal ECM ground. And when you put the old ECM back, everything goes back to normal.

What are your long term fuel trims with the stock ECM? If it's running rich on the stock ECM, you probably have a vacuum leak somewhere which the mkiv 1.8t is notorious for. Fix your vacuum leaks before you tune.

If you can return the tuned ECM, I would just send it back and tell them to send you a new one.

It's probably a cracked solder joint for the connector or bad inductor which separates the car ground and sensor ground inside the tuned ECM. If you open it, you probably void whatever warranty they promised (if any).

Edit: also those connectors look fine. Nothing out of the ordinary as far as I can tell
Its a used ECU sadly. I never noticed any drivability issues. I have smelt fumes every now and then but i did a muffler delete (i know i know) and thought it just came with the territory. Ill be bringing it to my local euro shop to see if they can do a smoke test. Would it be possible for an air leak to cause the same issues as well? Ive talked to the PO and he said hes used the tune on 2 vehicles and both ran perfect.
 

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Nothing wrong with a muffler delete, sounds cool but there's a lot of drone on the highway. Shouldn't affect your engine as long as it was after the cat.

P0237 Map sensor signal too low
P0343 Camshaft position sensor signal too high
P0103 MAF signal too high

In addition to the sensors above, your IAT, CTS, knock sensors, and engine speed sensor share the same ground.

Vacuum leaks won't cause those errors. At most a vacuum leak will cause some idle issues. Sounds like the PO of the tuned ECM may have burned you.

Just to confirm, what's the part number on the ECM?
 

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Discussion Starter · #11 ·
Nothing wrong with a muffler delete, sounds cool but there's a lot of drone on the highway. Shouldn't affect your engine as long as it was after the cat.

P0237 Map sensor signal too low
P0343 Camshaft position sensor signal too high
P0103 MAF signal too high

In addition to the sensors above, your IAT, CTS, knock sensors, and engine speed sensor share the same ground.

Vacuum leaks won't cause those errors. At most a vacuum leak will cause some idle issues. Sounds like the PO of the tuned ECM may have burned you.

Just to confirm, what's the part number on the ECM?
The part number is the same on the tuned and my original ECM. It is 06A 906 032 DL.
Would you say there is any other reason that could be a cause other than this ECM? As in stuck injector or anything like that? I don't really know if the PO would take it back and that'd leave me in the hole but if its not worth trying to fix I don't want to keep chasing problems that aren't there. I appreciate all the help just trying to figure out what my course of action should be. Would getting my car read by VCDS be any help at all?
 

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Stuck injector would throw a misfire code for a specific cylinder, no?

I've run my golf with an injector unplugged because one of my coil packs went bad and it still ran decent on three cylinders for the few days while I waited for a new coil to come in lol.

VCDS would capture more trouble codes than a generic AutoZone scanner, so probably.

Do you have a multimeter on hand? Measure the resistance between pin 108 and pin 1 on the tuned ECM. I'll go measure my extra ECM as soon as I find it.

Edit: should be pin 2, not pin 1
 

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Discussion Starter · #13 ·
Stuck injector would throw a misfire code for a specific cylinder, no?

I've run my golf with an injector unplugged because one of my coil packs went bad and it still ran decent on three cylinders for the few days while I waited for a new coil to come in lol.

VCDS would capture more trouble codes than a generic AutoZone scanner, so probably.

Do you have a multimeter on hand? Measure the resistance between pin 108 and pin 1 on the tuned ECM. I'll go measure my extra ECM as soon as I find it.
I don't have a multimeter on hand, but can get one easily. Is there a diagram online somewhere with all the pins listed? I see some have numbers beside them but all. Let me know what the resistance reading should be and Ill see if I can get my hands on a multimeter tomorrow. My next day off is Wednesday so if I cant find any sign of an issue with the ECM I'll see if I can get my car read. Thank you for your time as always
 

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Discussion Starter · #14 ·
I don't have a multimeter on hand, but can get one easily. Is there a diagram online somewhere with all the pins listed? I see some have numbers beside them but all. Let me know what the resistance reading should be and Ill see if I can get my hands on a multimeter tomorrow. My next day off is Wednesday so if I cant find any sign of an issue with the ECM I'll see if I can get my car read. Thank you for your time as always
Ah found a thread with the image of them numbered. Well more so I finally saw that its just by row.. oops.
 

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After staring at the pcb traces of the ECM, there's actually no ground plane filter for the sensor ground. There should be no resistance (0-4 ohms) between pin 2 (also ground) and pin 108.
 

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Discussion Starter · #16 ·
After staring at the pcb traces of the ECM, there's actually no ground plane filter for the sensor ground. There should be no resistance (0-4 ohms) between pin 2 (also ground) and pin 108.
So in simpler terms what you're saying is if I find there is resistance between pin 108/2 then the ECM is bad/damaged? And the 0-4 ohms is the accepted range? As in if I see 2 ohms its okay but if I see 7 ohms its bad?
 

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0-4 is the typical range taking into account for resistance in the probes. What you're looking for is if you can't can't a stable reading or it's hundreds of ohms or greater.

If you're handy with a soldering iron, inspect for cracks in the following solder joint and touch up with some fresh solder if your resistance is too high.
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Discussion Starter · #18 ·
0-4 is the typical range taking into account for resistance in the probes. What you're looking for is if you can't can't a stable reading or it's hundreds of ohms or greater.

If you're handy with a soldering iron, inspect for cracks in the following solder joint and touch up with some fresh solder if your resistance is too high.
View attachment 183818
To be honest, I've never used a soldering iron in my life. If I do figure out this ECM is bad my first course of action would be attempting to return it to the PO. After that I may find someone to try to repair it for me. I appreciate all of your help and will be getting my hands on a multimeter asap, I'll make sure to come back here and let you know what happens.
 

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I mean, alternatively you can just open up the large ECM connector, pull back some of the harness insulation, and put a wire tap between pin 2 (brown/red) and pin 27 (green)

Pin 2, 27, and 108 are electrically connected internally. Putting a wire tap bypasses that solder joint, so it should be fine, just not the most elegant solution.

Edit: pin 27 is the MAF ground, just fyi
 

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Discussion Starter · #20 ·
I mean, alternatively you can just open up the large ECM connector, pull back some of the harness insulation, and put a wire tap between pin 2 (brown/red) and pin 27 (green)

Pin 2, 27, and 108 are electrically connected internally. Putting a wire tap bypasses that solder joint, so it should be fine, just not the most elegant solution.

Edit: pin 27 is the MAF ground, just fyi
Alright just tested pin 108 to pin 1 and then to pin 2 both have 0 ohms. What should be my next move? A vcds read + smoke test?
 
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