# ECU reading defective speed sensor



## FDonohue (Jul 8, 2003)

A couple of months ago the check engine light in my 96 Sentra 1.6l, 5-speed came on. A local service station read it a a defective speed sensor and ordered a new one from Nissan and replaced it. A short time later the check engine light came on again and it was the speed sensor again. Nissan replaced the speed sensor under warranty but now the check engine light is on again and it reads defective speed sensor. I can't believe speed sensors are going bad this often. Anybody have this problem or have any clues?


----------



## azkicker0027 (May 31, 2002)

but what speed sensor?? engine speed or vehicle speed???


----------



## FDonohue (Jul 8, 2003)

It is the vehicle speed sensor that is in the left rear of the transmission.


----------



## himilefrontier (Jan 21, 2003)

Does the speedo still work?If it is bad the speedo shouldn't work, otherwise you have some bad wiring.My 98 Frontier has 200k on it and has never needed a VSS so I think the problem may lie elsewhere in the circuit.


----------



## niky (Jul 20, 2002)

it's your wiring dude... you may have a short or a mis-sized fuse burning out your sensors.


----------



## FDonohue (Jul 8, 2003)

Thanks for your help guys. Yes the speedometer does work. Someone else suggested to me that there might be a bad ground so I guess I've got some troubleshooting to do.


----------



## Ninety-Nine SE-L (May 5, 2002)

here's how the speed sensor works:

Ground(-)---->Speed Sensor---->Speedometer---->ECU

As you can see, the signal (which I believe is negative) goes to the Speedometer.odometer before it gos to the ECU. There are 2 red wires going from the speed sensor to the speedometer. From the speedometer, the signal is carried through a purple/red wire to the ECU.

If it is not the speed sensor and the speedometer is reading fine, I would narrow your problem to:

1. The purple/red wire going from the Speedometer to the ECU is bad.
2. The speedometer/odometer unit is faulty and it is sending a bad signal to the ECU.
3. The ECU is bad.


----------

