Transmission stuck on fourth gear and speedometer fluctuates vehicle stationary

1998 AUDI A8
160,000 MILES • 4.2L • V8 • 4WD • AUTOMATIC
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SEVAG P
  • ASE Certified Mechanic
  • ASE Certified Mechanic
  • 405 POSTS
Hi,

Audi a8 1998 Quattro, automatic trasmission jumps up to 4rth gear and stucked at 4rth when vehicle is stationary at traffic until the engine is turned off and on, also speedometer flactutes at vehicle stationary (check video)fault codes at transmission are p0721 and p0703, I like the know the location of the transmission output speed sensor and it's wiring diagram,also want to know how to trouble shoot the fault code p0703, my brake lights are working properly, when the faults erased after test drive they appear again.
Thank you.
Dec 24, 2019 at 4:57 AM
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KASEKENNY
  • ASE Certified Mechanic
  • 18,907 POSTS
  • ASE Certified Mechanic
I included the wiring diagram and the testing for these codes. More than likely you have two issues. The speedometer issue is the speed sensor code and the stuck in 4th gear is the torque converter getting stuck on. That is most likely the second code.

Let me know if you have questions. Thanks
Dec 25, 2019 at 3:52 AM
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SEVAG P
  • ASE Certified Mechanic
  • 405 POSTS
  • ASE Certified Mechanic
Thanks for your reply, I will check the wiring before replacing any component when the problem solved I give you feed back what happens with me.
Thank you
Dec 25, 2019 at 7:05 AM
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