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    Thread: code P1542 HELP!!!! car works irratically!!

    1. 06-22-2007 08:07 PM #1
      on the highway in stop-and-go traffic all the sudden my car throws an EPC, CEL, and the ASR light came on. i wasn't gassing or anything just sitting on the highway. i'd get on the shoulder and restart the car and then it would do it again after like 5 mins.
      it seems only to do it when i'm at idle or when my boost gauge is in vacuum.
      i stopped and got the code on the way home:
      code P1542
      google says thats:
      "Throttle Actuation Potentiometer Range/Performance"
      it seems to work fine then it'll just crap out all the sudden!
      here's a link to another of my threads with some detailed history:

    2. 06-22-2007 08:18 PM #2

    3. 06-22-2007 08:38 PM #3
      again bump

    4. Banned lpbudV's Avatar
      Join Date
      Jun 4th, 2006
      06-22-2007 09:02 PM #4
      sounds like you MAF took a poop, r u using a k&n filter?

    5. 06-23-2007 12:28 AM #5
      nope definetely a filter i got at auto zone, it wasnt k&n it wasnt even cone shaped. it was a blue half circle shaped filter. would that do it???
      would a MAF throw a throttle body code like that??
      by the way, another weird thing. i took the diode off and it'll still boost all the way up to 17 psi without going into limp again WITH NO DIODE what does that mean??? is my MAP or MAP wires screwed up???

    6. 06-23-2007 12:30 AM #6
      also i have a CAI so thats where the filter is.
      also not chipped or flashed and thats why the diode-less high psi is shocking.

    7. 06-23-2007 09:20 PM #7

    8. Member Chupathingy's Avatar
      Join Date
      Aug 1st, 2005
      2012 Mini Cooper S Hardtop
      06-23-2007 09:51 PM #8
      sounds like there is a problem with your throttle body. my old gti's tb fried and had to be replaced.
      Check the harness underneath it to make sure its still even plugged in, or if there is a crack in one of the wires. Also clear the codes and perform a throttle alignment. If that doesn't do it start looking for a new one. sorry bro

    9. 07-02-2007 05:51 PM #9
      I've been gone for a while and now that I've returned I've been back into working on fixing this problem.
      Got some new codes:
      Any more insight?
      Also its interesting that every time I either clear the cel or unplug the battery the car returns to working fine for a couple of days.
      thanks for any help!

    10. 07-02-2007 06:02 PM #10
      throttle body issue is the most likely cause. may need to be cleaned and then adapted. also, if your battery has something wrong with it, and the voltage drops too low, it can cause the basic setting of the throttle to be lost. the epc and asr lights are related to traction control. the throttle is involved with all of this as the car cuts off the throttle in slippery situations. even though your car is not slipping, a funky throttle causes the same "cut off" of power like the asr system would cause. hence the lights flashing. my guess...you need a throttle body, or a battery. more likely the throttle body.

    11. 07-02-2007 06:08 PM #11
      do you think if I cleaned the throttle body that would do the trick? Anyone know how to remove a throttle body on a 1.8t jetta or gti?

    12. 07-02-2007 08:15 PM #12
      cleaning it is usually the first step...then you have to adapt it. if the fault c omes back...most likely the throttle body is bad. i believe there is a diy somewhere on how to clean it in the mkiv faqs. basically, it is 4 5mm allen head bolt that hold it onto the intake manifold. you also have to remove the upper intercooler hose, and a vacuum hose that is connected to the top of the throttle body. once out, get some brake cleaner, or carb cleaner and clean the butterfly and all around it. you'll most likely want to get a new gasket for the throttle body, although i have done it without replacing it, and it doesn leak, or cause problems. you can clean it by taking off just the upper intercooler hose, and opening the butterfly horizontal with your fingers, then spray cleaner inside and wipe around with a rag. do not spray alot into the open throttle plate or else you could hydrolock the motor. just a few quick spurts then a wipe around. also if you do it this way, the car will usually start funny as a little of the cleaner gets into the the combustion chamber. dont be alarmed, it will go away after a few seconds. if you are not sure how to do this, take it to the dealer, or look for the diy. good luck.

      Modified by stirfriedx9 at 5:16 PM 7-2-2007

    13. 07-04-2007 02:31 PM #13
      so I just cleaned the throttle body (I couldnt get it off the intake mani so I just cleaned it from the intercooler inlet side). Man is that thing dirty!
      So next question: how do I "adapt" it? I've heard its done with a vag com but I don't have one. Will it not be really fixed until I do adapt it? Any one with a vag com near 80127 wanna help a brother out?

    14. 07-05-2007 03:22 PM #14
      iPhone bump

    15. 07-06-2007 07:29 PM #15
      After ultimate frisbee bump.

    16. 07-06-2007 09:12 PM #16
      Quote, originally posted by danjoekir »
      so I just cleaned the throttle body (I couldnt get it off the intake mani so I just cleaned it from the intercooler inlet side). Man is that thing dirty!
      So next question: how do I "adapt" it? I've heard its done with a vag com but I don't have one. Will it not be really fixed until I do adapt it? Any one with a vag com near 80127 wanna help a brother out?

      You need someone with a full registered VAG-COM to do the adaptation. The shareware version will not allow it. The "key in the ignition" method does not work.
      I'll also bet there is still quite a bit crap on the inside of the throttle body where you couldn't get to. Before you have someone do the adaptation, you might want to remove it, clean the inside, replace the gasket, and then do the adaptation. But also keep in mind that your TB could have gone bad. It is a 2001 and they have been known to fail. The adaptation may not solve the problem.

    17. 07-06-2007 09:48 PM #17
      so where could I get it done? Is it pretty expensive? The car hasn't freaked on me in a little while but it acts fine up until it happens. It does feel a slight bit smoother but I bet there is still some junk in there. I tried to take it off to clean it but I couldnt get it off the intake mani. If it comes up again i'll totally do all that.

    18. 07-10-2007 12:42 AM #18
      so its still been a while since the car acted up. Maybe a cleaning was all that was needed.

    19. Member
      Join Date
      Jul 15th, 2012
      Pittsburgh, Pa
      03 gti 24v vr6
      07-31-2012 11:46 PM #19
      Have you had any problems since then?

    20. n00b
      Join Date
      May 23rd, 2012
      Jetta 01 1.8T
      10-16-2012 10:10 PM #20
      I have the same problems as you described. P1542,P1171,P1297 those codes are couple weeks after installed the new TB.
      The mechanic said could be a bad wires. It is taken to much time to find the problem.
      One more thing, I have the K&N filter. It will make a big difference?

    21. Member Slimjimmn's Avatar
      Join Date
      Apr 8th, 2006
      Rochester, MN
      MK4 shaggin wagon
      10-16-2012 10:40 PM #21
      filter directly on the maf will cause many issues and codes.
      Only a filter with a velocity stack will prevent codes.

      check out my thread for TB connector replacement. The factory harness is built too short and the wires pull out of the connector over time.

      the car is on an inclined driveway and up on jack stands in the front only
      04 Jetta Wagon 2.slow------>Family man now

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