Question about 1993 GMC Sierra C2500

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What is the proper voltage setting at idle ??

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It should be somewhere between 12 and 14 volts. The more options, like lights,A/C, brake lights ect. that you turn on the reading will change. But it should stay between 12-14 volts.
I hope this helps .

Posted on Sep 24, 2009


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Check the TPS (Throttle position sensor) wire lead and replace the TPS if any signs of damage or failure.

The Throttle Position Sensor (TPS) is used to send input signals to the Powertrain Control Module (PCM) to indicate the current angle of the throttle blade.

This sensor is a variable resistor that has a 5 volt reference signal applied to it by the PCM. The TPS sends signals back to the PCM in the range of approximately 1 to 4 volts, depending upon the throttle shaft angle. The PCM uses these input voltages to determine the current position of the throttle.
The PCM uses the voltage signals from the TPS and other input sensors to determine the proper air/fuel mixture and ignition timing for certain operating conditions. Some of these operating conditions are: acceleration, deceleration, idle, and wide open throttle.

Typical Readings:
An input voltage of approximately 1 volt indicates a minimum throttle opening, idle, or deceleration condition. An input voltage of approximately 2 volts indicates a cruise or light acceleration condition. An input voltage of approximately 4 volts would indicate a maximum throttle opening or wide open throttle condition.
NOTE: The following procedure tests the TPS only.
  1. The TPS can be tested with an analog voltmeter. The center terminal of the TPS is the output terminal.
  2. With the ignition key in the ON position, check the TPS output voltage at the center terminal wire of the connector. Check this at idle (throttle plate closed), and at wide open throttle (WOT).
    • At idle, TPS output voltage should be approximately one volt. The output voltage should increase gradually as the throttle plate is slowly opened from idle to WOT.
    • At wide open throttle, TPS output should be approximately 4.5 volts.
As always, check the service manual for the proper procedures and specifications for your particular vehicle.

Thank you using Fixya and good luck.

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