ECM not reading vehicle speed

Tiny
TIM LISS
  • MEMBER
  • 2009 HYUNDAI ACCENT
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 125,000 MILES
After taking a exit off of interstate, the check engine light illuminated. Went and had it scanned at local Autozone and was told it was "vehicle/transmission speed sensor". I replaced both the input and output sensors located on transmission. After maybe sixty miles, check engine light illuminates again. This time I go have it hooked up to a computer scanner. While driving the car down the road the ECM is showing that I am going zero mph. Is it the ABS wheel speed sensor that sends that information to the ECM or does someone know which sensor sends that information?
Monday, February 6th, 2017 AT 8:29 PM

3 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The transmission sends the vehicle speed, however this may be a shorted wire or poor connection the ECM may not be getting the signal so it could be a wiring or computer problem.
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Tuesday, February 7th, 2017 AT 6:38 AM
Tiny
TIM LISS
  • MEMBER
  • 2 POSTS
Thanks for your reply. I forgot to mention that the speedometer and rpm gauge seems to work fine just not getting to ECU.
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Wednesday, February 8th, 2017 AT 2:40 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,347 POSTS
Hey Tim,

It sounds like you have a broken wire, here is a wiring diagram and a guide to help you check the problem further. It the wiring checks out check for voltage output at the sensor and if seems like that it working then the ECM is bad and needs replacement.

https://www.2carpros.com/articles/how-to-check-wiring

Please run some tests and get back to us so we can continue helping you.

Best, Ken

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Monday, February 13th, 2017 AT 9:24 AM

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