Vehicle Speed Sensor

ROSALYNN99

MEMBER
SATURN

Saturn SL 1998 4liter 95,645 miles

I cannot pass my emissions test because my vehicle speed sensor is malfunctioning. I have had it replaced and have done the cold start, drive cylcles, and even had the code cleared. Previous to having the sensor replaced my Service Engine soon light had been on. Once I had replaced the sensor the light went off. It stays off until the service station plugs my computer in to run an emissions test. Once plugged in the Service Engine soon light comes on and I fail emissions. I get a P0500 code and sensors that previously read 'ready' on the test now read 'not ready' (Catalyst. Evap Sys, O2 sensor, and EGR sys) Is there anything more I can do to get this sensor to read right? Should I replace it again?

4 Replies

2CARPRO JACK

MECHANIC
11,533 POSTS

Just to clarify, VSS replaced and codes cleared, no check engine light. Plug the smog machine in and the MIL light comes on and P0500, and monitors not ready. How long since codes cleared? Takes about 40-50 miles of actual driving to reset enough monitors to do the emissions test

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Friday, February 2nd, 2007 AT 7:34 AM

ROSALYNN99

MEMBER
3 POSTS

Correct. Replaced, Cleared, no light until plugged in. The code was cleared almost a week before I took it back in to be tested. I had driven almost 200 miles since the code was cleared.

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Friday, February 2nd, 2007 AT 9:51 AM

2CARPRO JACK

MECHANIC
11,533 POSTS

Now comes the fun part. Car needs to be on a scanner to watch speed if moving greater than 3mph and vss reads then problem is intermittent. Otherwise be sure Vss is tightened to 20 ft lbs. Test Vss terminals for resistance 800-1600 ohms or the sensor is bad. Then test wires to PCM the resaistance should be 800-1600 ohms as well. If all ok then the PCM could be bad which would explain the monitors reseting

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Friday, February 2nd, 2007 AT 1:32 PM

ROSALYNN99