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Unread post by ccoleman42 » Tue Aug 14, 2018 2:51 pm

I have a 1993 Buick Riviera and I replaced the throttle position sensor and disconnected the battery and the check engine light is still on and I'm getting a code of 21 which means the throttle position sensor is getting a high voltage. What else can I do?

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Re: Voltage

Unread post by carriedi » Wed Aug 15, 2018 11:29 pm

since you can get a code, can you get voltages?

with your key on engine off, the TP signal should read below 1 volt in the idle position. That should be the dark blue wire. Verify that you have 5V on the gray wire. the other wire should be the ground (it can be black, tan or orange) If you have 5V (or very close to it) then you should get a reading of less than 1 volt on the signal return at the idle stop position. Verify that the voltage moves steady without glitches to about 4.5 volts as you move the throttle to wide open throttle and then back down to idle stop. If everything looks good for the sweep (and it should with a new sensor) If your idle stop reading is over 1 volt see if you can adjust your idle screw to lower that voltage reading. If your idle is turned up too much, it moves your tps sensor. If you can get the sensor voltage under 1 volt then it should stop setting the code.
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