ECM not reading vehicle speed

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?

3 Replies

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

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

KEN L

MASTER CERTIFIED MECHANIC
47,643 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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