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    VWVortex


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    Thread: check engine light on code p0688

    1. 12-16-2007 03:33 PM #1
      my car was left in the rain overnight with the hood off, then i got it back and the battery was running almost dead, so as i was at sears buying a new battery i was trying to start the car and drive it into the shop to get it changed when it was having a lot of trouble turning over, i mean to the point where i didnt think it was going to start it finally turned over and along with the engine turning over the chekc engine light came on so i got the new battery and took it to autozone and tested it with the bdt2 kit and found out it was a p0688 code. i'm going to tak eit vw ause i do have a warrenty but i dont want to drive it till then cause i read it could fry my ecu. i also read that having a low battery could trigger this error message so i'm not quite sure what to do. anyone know anything about this?

    2. Banned lpbudV's Avatar
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      12-16-2007 04:42 PM #2
      Quote, originally posted by 95GrannyGolf »

      It's not the connector exterior that causes issues, it's a buildup of corrosion between the connector and its mating surfaces on the interior. Corrosion doesn't conduct electricity well.

      Best for push-on connectors is repeated mating and removing with electrical contact cleaner available at an electronics repair place, with possibly some tightening up of the mechanical connection by gently bending the bits that grab terminals.

      For bolt-down connections, nothing beats wire brush, anywhere from 80 to 150 grit wetordry (emory), sometimes even a small file. When you can clean both (top & bottom) surfaces of a ring connector, plus all flat surfaces around the bolt/stud, plus the stud threads, that's ideal. (Access may limit what you can do, of course).

      On my GolfIII::
      On both ground and power sides, I found significant corrosion on the TCU and ECU connectors, corrosion between the ECU, its carrier, and the plenum where it mounts, bad corrosion on the engine grounds, bad corrosion on the ground strap from coil to head... though you won't have the latter.


      Modified by 95GrannyGolf at 6:47 AM 5-20-2007


    3. 12-16-2007 04:43 PM #3

    4. 12-16-2007 05:38 PM #4
      i read all the posts about this error before i posted, but i also read something on another board that stated that a dying battery could throw a false signal out, which is what i'm hoping it is, i also spoke to my friend who is a tach at my local dealer who said it also could be a false signal going by the time the light came on, but if its not it should be covered by warrenty. either way i was looking for anyone else who seen this error.

    5. Senior Member bluefox280's Avatar
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      12-16-2007 08:02 PM #5
      * VW DTC 17072 (P0688) - ECM Power Relay Load Circuit (J271) -Open Circuit

      First, is the engine coolant fan running at full Speed while ignition is OFF and engine is COLD?
      That leads to a to discharged battery...
      Second, checked all appropriate fuses? Along with the power supply relay for the ECU?
      Also, terminal 87 could be faulty or hanging out...

      - Erik

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    6. 12-16-2007 08:17 PM #6
      Quote, originally posted by bluefox280 »
      * VW DTC 17072 (P0688) - ECM Power Relay Load Circuit (J271) -Open Circuit

      First, is the engine coolant fan running at full Speed while ignition is OFF and engine is COLD?
      That leads to a to discharged battery...
      Second, checked all appropriate fuses? Along with the power supply relay for the ECU?
      Also, terminal 87 could be faulty or hanging out...

      - Erik


      god bless you erik.

    7. 12-17-2007 12:50 PM #7
      i have an apt for VW on thursday, hopefully its nothing, but we'll see then and hopefully my warrenty will cover it

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