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EPC light + exclamation point over odometer

MrFancypants

Autocross Champion
I brought my stock GTI to a dealership to get a new timing chain tensioner in it. When I dropped it off it was healthy, no issues.

When I got it back and got it on the road I noticed the EPC light and the exclamation point, although the exclamation point went away when the car stopped moving.

As I understand it there's something going on in the intake/throttle system. Is it possible that either the noise pipe or turbo outlet pipe were installed incorrectly and there's a boost leak?

What other reasons could there be for this? It seems unlikely that my car would just decide to show a new issue unrelated the job they performed. I accept that it's possible, but it seems far fetched.
 

MrFancypants

Autocross Champion
I never got the code, but I did drive it back immediately so the service adviser saw the issue. After another day of messing with it they couldn't find anything wrong with the car. They cleared the ECU and after a long test drive the problem never came back.
 

MrFancypants

Autocross Champion
So it happened again this morning.

When the EPC light came on the exclamation point next to the cruise control symbol also came on. First symptom was limp mode was on, so no acceleration above 3000 RPMs.

I shut off the car and restarted it and both lights came back on, but a moment later the EPC light turned off. The exclamation point / cruise control thing stayed on the rest of my drive to work, but it did turn off when the car was at a stop. Thinking that maybe what I was seeing was the car telling me there was a problem with the cruise control system I tried using it and predictably it didn't work.

At lunch when I turned the car on to drive it to Autozone to get codes it was back to normal, and... no codes.

Because I didn't ask for the codes when the problem was present at the dealership, all I got was the service adviser's thoughts that it was either the throttle body going bad or maybe the gas pedal.

I researched the problem via Google and I found the EPC light + exclamation point problem being reportedly resolved in these ways:

1. Old battery going bad, causing odd electrical issues. My battery is only a few months old so this seems unlikely

2. Turn signal stalk gone bad. Those who reported this as the fix also stated that the lights usually came on when they used the turn signal, this is not the case with my car. That and I believe that in order to change this part the steering wheel has to come off, so I won't be bothering with that just yet.

3. Throttle body wiring harness issues. TSB 01-09-04, which addresses 2008 and 2009 TSI equipped cars (and earlier 2.0 cars), offers a fix for cars with these symptoms. It also identifies codes for the throttle control valve and pedal position sensors. It makes sense that the cruise control system would freak out if the drive-by-wire throttle body wasn't working properly. The TSB is dated December 2009, my car was built in July 2009.







I'm guessing #3 is what will resolve my car's issues.

It's not surprising that this isn't a thing that most MkVIs have an issue with, and I suppose I shouldn't be too surprised that the dealership didn't identify this TSB as my car's model year fell out of the date range. The problem may have made itself known if the dealership was a little rough when they changed my intake manifold last year, or maybe I moved the engine around a bit too much when I changed out the engine/transmission mounts.
 
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MrFancypants

Autocross Champion
Not my car or my picture, but here's that exclamation point:

 

MrFancypants

Autocross Champion
I'm going to keep posting about this in here to document it. I no longer need advice so much as I'd like to make it easy for someone to diagnose this if it happens to them.

My car freaked out again today. I shut the car off, jiggled the wiring leading to the throttle body, fired it back up, and was given the "check engine" light in place of the EPC/cruise control warnings.

Off to AutoZone to be give a printout which reads..... P0221.

Yeah so, I guess I need to perform the TSB and this'll go away.
 

MrFancypants

Autocross Champion
Seen this happen a ton. Throttle issues are notorious on these cars.

Yeah, and I'm noticing an issue my car has had that I thought was just something the GTI did. At low speed, low RPM, first gear, it bucks violently when it shouldn't. It makes stop and go traffic annoying because the only way I can keep the car smooth is by using the clutch to smooth out the bucking. Do note that engine speed is above idle, so it's not bucking caused by trying to stop the car with the clutch engaged.

After I jiggle the wires a bit and push on the plug to reseat it (or whatever it needs) it actually smooths this out. For all these years I thought it was lazy low engine speed tuning by VW, because I only ever have the clutch engaged at around 1000 RPMs if I'm crawling in traffic, it's never that low in any other gear so I never bothered to see.
 
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MrFancypants

Autocross Champion
Finally got off my butt and ordered the rest of the parts I needed for this, along with a few other items my car needs (windshield washer fluid reservoir neck broke, wtf).

I'll report back in about six more months when I finally get to doing the repair, or whenever I get tired of pulling off on the shoulder to get my car out of limp mode.
 

MrFancypants

Autocross Champion
I finally got around to this. I didn't bother with it because the problem just went away. Then I had some A/C work done and I guess they had to fiddle with that part of the wiring harness and the issue returned. Last week I was almost left stranded because it wouldn't idle after starting.

Anyway, I repaired the wiring harness as described in TSB 01-09-04, and so far so good. In fact, if your car has issues with throttle control at low engine speeds or it shudders a bit when first applying throttle, you should consider doing this. For the longest time when moving back to the throttle after braking and entering a corner I'd get a bit of a shudder when opening the throttle. This fixed that.

I'll see what I can do to fix those broken pictures.
 

Carlosfandang0

Drag Racing Champion
I finally got around to this. I didn't bother with it because the problem just went away. Then I had some A/C work done and I guess they had to fiddle with that part of the wiring harness and the issue returned. Last week I was almost left stranded because it wouldn't idle after starting.

Anyway, I repaired the wiring harness as described in TSB 01-09-04, and so far so good. In fact, if your car has issues with throttle control at low engine speeds or it shudders a bit when first applying throttle, you should consider doing this. For the longest time when moving back to the throttle after braking and entering a corner I'd get a bit of a shudder when opening the throttle. This fixed that.

I'll see what I can do to fix those broken pictures.



Interesting! I to have had the bucking you describe (and still do to some extent), I did a throttle body alignment with VCDS which made it better I think but that could have been a placebo effect, I recently had the lower front control arms replaced along with the bushes and that’s made a difference to the bucking too but I’ll definitely look into doing this also!


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Carlosfandang0

Drag Racing Champion
I don’t get any of the other symptoms however so maybe it’s different for me!


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smanierre

Autocross Champion
Would replacing the throttle body fix this? I plan on doing a larger throttle body soon and if that will fix it i'll just do that. Or would I still need to replace the harness as well?
 

MrFancypants

Autocross Champion
Interesting! I to have had the bucking you describe (and still do to some extent), I did a throttle body alignment with VCDS which made it better I think but that could have been a placebo effect, I recently had the lower front control arms replaced along with the bushes and that’s made a difference to the bucking too but I’ll definitely look into doing this also!

Something to keep in mind is that because this is an electrical issue, we may not get the same exact symptoms between two different cars. Given that there are six wires going through the plug you may see different throttle body control issues that feel different from behind the wheel. The TSB listed something like four different possible error codes and I only ever saw one of them.

At first I even thought the off throttle to on throttle lurch was worn out motor mounts. I replaced the motor mounts and the problem didn't go away.

In fact, all of the minor driveability symptoms were there all of the time, even if the extreme bucking in 1st gear at 1000 RPMs with the clutch fully engaged and just rolling was minimized when I unplugged the throttle body and then plugged it back in.

So you may not have the more extreme issues I was having with the car not able to idle and still benefit from replacing the plug on the wiring harness.

What was the build date on your car? The closer it was to the end of the 2009 model year production the more likely it seems that this could be an issue, given the information in the TSB.


Would replacing the throttle body fix this? I plan on doing a larger throttle body soon and if that will fix it i'll just do that. Or would I still need to replace the harness as well?

If you're experiencing these issues I guess it's possible that it could be the throttle body and not the wiring harness. But given the existence of the TSB I placed my bet on the wiring harness. If the problem is the wiring harness, replacing the throttle body will not fix it. When you plug it back in the problem may go away, because that's how I lived with it for a couple of years, but in my case the problem came back.
 
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