1997 SC DOH 1.9 Automatic.. Check engine light is intermittingly going on and off. I thought it was the gas cap. I tightened it and it went off for awhile then came back on. So I bought a new cap and the light went out for 2 days then came back on. The Speedometer started misreading and the cruise control wasnt working properly. When the light came back on I brought it to have the engine code read. P0721 (output speed sensor circuit range).


I located the sensor using YouTube and physically located it on the car from the topside. It looks likeit will be easier to reach from underneath.


Will replacing the sensor fix my problem or could there be something else giving me the error code? I would like to get someone else's opinion on this. Thanks


I called Advance Auto Parts and ordered a new one, should be in tomorrow.Edited by: rickatom

 

Just my opinion but there's usually something with the wiring to the speed sensor that tears or rips the wiring from snow, rain, road debris, etc., unless the 'teeth' are broken. When you crawl under the car you'll get a better look at everything.

 

Even though I do not have the new part yet, I wanted to see what I had to do. I put the car up on some ramps, got a flat screwdriver and an adjustable wrench. I unpluged the wire connection careful not to break the clip with the screwdriver, and easily unscrewed to the sensor with the wrench. I was surprised not to seea mechanical feature to it. Just a magnet in the center of it. I took my finger and put it in the threaded hole and felt the splines inside the transmission. I guess the sensor reads on these splines.


Anyway I put it back together and will have to get the new part tommorrow and hopefully this will fix my problem. I am wondering, will I have to get the computer reset or will it do it itself???Edited by: rickatom

 

The splines should be evenly spaced as they pass by the magnetic pick-up unit you removed. Sometimes road debris gets in there as well as fine metallic dust sticks to the magnet. Clean as much off and if possible shine a light into the hole while rotating the wheel hub to be sure there isn't a broken tooth.

 

When I put the old part back in yesterday, my daughter took the car uptown. She called me in a frantic. She lost her brakes and could not stop properly. She had to pull over and stop.


When I got to her, in just a few minutes, she had parked and switched off the key. I got in the car and started it up. The check light had gone out, but the brake pedal was real weak. As I proceeded home, I kept hitting the brake and it appeared to build back up. The speedometer was working fine again.


She drove the car last night, and the light came back on, but she said it drove fine.


I am going to change out the sensor this morning in hopes that it clears the problem. I dont understand what it would have to do with the braking system though. Any Ideas???

 

replaced the old sensor with the new one. The idiot light was still on, but I expected that. Drove the car to the shop and had the computer reset. Then I drove for a few miles, up the interstate using the cruise control and back, then shut the car off and restarted it again. The light did not come back on.


I am hoping my worries are over.....