# Weird EPC & Traction Control Light issue...



## micker (Aug 8, 2010)

I've been wrestling with a weird issue with my jetta for about three weeks now. I'm hoping someone might be able to shed some light on this. I have a 2005.5 2.5 with 80k on it. 

About three weeks ago I started it up and it ran really rough like it was going to stall. I gave it some gas, let it warm up and after a couple minutes I turned it off and started it up again. It ran much better, but still a little rough. After a half mile of driving the EPC and traction control lights came on. I got it home and the next morning took it to my mechanic to get it scanned. When I turned it on that morning, it ran fine and the indicator lamps were off. 

My mechanic scanned it and we got these codes: 
P16505 Throttle Position sensor (g69) implausible signal P0121 
P16605 Angle sensor for throttle (g18 implausible signal P0221 

The mechanic said it was probably a bad sensor but we would have to put a new throttle body in it as the sensors aren't available separately. 

I ordered a reconditioned throttle body and we installed it the next week. After installing the throttle body it ran fine. Everything was perfect, no rough running or idle. It ran great like this for two days, then the EPC and traction control indicator lamps came back on. We scanned it again and got the exact same codes as before: 
P16505 Throttle Position sensor (g69) implausible signal P0121 
P16605 Angle sensor for throttle (g18 implausible signal P0221 

I posted to another Jetta board and got a whole bunch of responses that it's most likely a dirty MAF, so I ordered the weird 5 lobe tamper proof torx, took the MAF out and cleaned it. It didnt look dirty, but gave it some break cleaner action just to be safe. After putting it back in the car ran great. Everything was back to normal. I drove it all over for work with no problems. I took it on a short work trip (200 miles each way) and everything was fine on the way out and while I was there, but on the way home the indicator lamps (EPC and traction) came back on again. I scanned it and again got the same codes. 

The jetta guys I had been discussing it with said it still sounded like a bad MAF. I ordered a new MAF for it and put it in last Friday. The car ran fine again, but only for a few hours this time. I took my wife out for dinner and drove to test it out. It was fine on the way there and then on the way home the same indicator lamps came back. 

I got it scanned again the next morning. Same codes: 
P16505 Throttle Position sensor (g69) implausible signal P0121 
P16605 Angle sensor for throttle (g18 implausible signal P0221 

I was at wits end at this point. I figured the only thing I hadn't changed out in the intake system was the air filter. Last Sunday I pulled the engine cover off and replaced the air filter. The filter was dirty, but not terribly so. Regardless I replaced it with a new one. Amazingly, the indicators that were on went away and it ran great! It ran all week just fine. Better than it had since this whole thing started. I couldn't believe that it was the air filter causing these problems, but it sure seemed that way. 

Then this morning I started it up and it was really rough, like it was going to stall. Just like it did the very first time this happened. I let it warm up and the idle steadied, but a block away from home I got the same indicator lamps. 

What could be causing this? 

The only thing I can think of now is that I must have a short somewhere and pulling the engine cover off, replacing the throttle body and the MAF is causing me to move whatever wire is bad and let it get a solid connection. 

Any ideas? Anyone ever seen this happen before?


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## micker (Aug 8, 2010)

hmmm... didnt realize this was the same board as vwvortex... I posted this issue there as well earlier tonight. Mods can delete this if necessary.


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