Mechanics

THE SPEEDOMETER QUIT WORKING AND IT'S MESSING WITH THE TRANSMISSION.

1991 Toyota Previa • 500,000 miles

After a long haul pulling a car and trailer my speedometer quit working. It seems to be messing up the transmission on highway speeds telling it to shift gears when it shouldn't be. My job relies on this vehicle and would like to attempt to fix it myself if you have any advice. I can't get in to see a mechanic right away and I'm scared I'm going to either break down or get pulled over because I don't know how how fast I'm going!
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Alexleahdullernorris
September 6, 2012.




Do you have a multimeter to do some testing?

Saturntech9
Sep 6, 2012.
No I don't

Do I need one to find out what the problem is? Or is there another way?

Get a scan done to check for trouble codes. Most parts stores provides free scanning services.

Most likely the Vehicle Speed Sensor or its circuitry is faulty. Do not jump to conclusion that the sensor is bad. It could be a loose wire or a bad circuit.

KHLow2008
Sep 6, 2012.
Not too sure about obd1 code scanning I know they do obd2 but obd would be a lo harder for them with all the connectors scan tool etc.

Saturntech9
Sep 6, 2012.
http://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995

Japanese makes comes with a flash code retrieval for pre-OBD-II models.

Most modern scan tools comes with adapters for code retrieval for these but some are not compatabile as the ECM/PCM are not designed for scan tools as they are like those with sight windows which don't have any scan tool plugs.
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KHLow2008
Sep 7, 2012.

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