TEST 1: Testing The 5 Volt Reference Signal

Making Sure The TPS Is Getting Power. How To Test The Throttle Position Sensor (GM 4.3L, 5.0L, 5.7L)

The engine on your GM car or truck must be fully warm (normal operating temperature) to successfully diagnose the throttle position sensor. So, if it's not warmed up already, go ahead and crank her up and get her warmed up.

The first test is to verify that the throttle position sensor (TPS) is getting power, which in this case is 5 Volts. this voltage comes from the PCM (Powertrain Control Module=Fuel Injection Computer). Here are the test steps:

  1. 1

    Disconnect the throttle position sensor from its electrical connector.

  2. 2

    Place your multimeter in Volts DC mode.

  3. 3

    With the red multimeter test lead, and an appropriate tool, probe the circuit labeled with the number 3 in the photo.

    NOTE: If you probe the front of the female terminal (that connects to the wire), be careful and don't damage it with the multimeter's test probe.

  4. 4

    Connect the black multimeter test lead directly on the negative (-) battery terminal.

  5. 5

    Turn the key to its ON position but do not start the engine.

  6. 6

    Your multimeter should read 4.5 to 5 Volts.

Let's take a look at what your test results mean:

CASE 1: The multimeter registered 4.5 to 5 Volts. So far so good since this confirms that the PCM on your GM vehicle is providing power to the TPS. The next step is to test the Ground circuit, go to: TEST 2: Testing The Sensor Return (Ground) Circuit.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts. Then the fuel injection computer is NOT providing the voltage that the TPS needs to operate.

This missing voltage could be the result of an open-circuit problem in the circuit or the PCM may be fried. Altho' testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your GM vehicle as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TEST 2: Testing The Sensor Return (Ground) Circuit

Making Sure The TPS Is Getting Ground. How To Test The Throttle Position Sensor (GM 4.3L, 5.0L, 5.7L)

Now that you have verified that the TPS on your GM car or pick up is getting power, you need to check that it's also getting a good Ground.

The PCM is the one that completes the path to Ground for the TPS internally. Therefore, be careful. Do not accidentally or intentionally short this wire to power or you're gonna' have a fried PCM on your hands.

  1. 1

    Disconnect the throttle position sensor from its electrical connector.

  2. 2

    Place your multimeter in Volts DC mode.

  3. 3

    With the black multimeter test lead, and an appropriate tool, probe the circuit labeled with the number 2 in the photo.

    NOTE: If you probe the front of the female terminal (that connects to the wire), be careful and don't damage it with the multimeter's test probe.

  4. 4

    Connect the red multimeter test lead to the battery positive (+) terminal.

  5. 5

    Turn the key to its ON position but don't start the engine.

  6. 6

    The multimeter should display 10 to 12 Volts.

Let's take a look at your test results:

CASE 1: The multimeter displayed 11 to 12 Volts. This test result tells you that the PCM is feeding a good Ground to the TP sensor.

The next step is to verify that the TP sensor is creating a good throttle position signal the PCM can use, go to: TEST 3: Testing The Throttle Position Sensor Signal.

CASE 2: The multimeter DID NOT display 11 to 12 Volts. Then the PCM is NOT supplying a ground either because of an internal fault/problem or there's an open in the wire between the TPS and the PCM itself.

Altho' testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your GM vehicle as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

Buick Vehicles:

  • Roadmaster 5.7L
    • 1996

Cadillac Vehicles:

  • Escalade 5.7L
    • 1999, 2000
  • Fleetwood Brougham 5.7L
    • 1996

Chevrolet Vehicles:

  • Astro 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • TrailBlazer 4.3L
    • 1999, 2000, 2001

Chevrolet Vehicles:

  • Silverado C1500, C2500, C3500 4.3L, 5.0L, 5.7L
    • 1996, 1997, 1998, 1999, 2000
  • Suburban C1500, C2500, C3500 5.7L
    • 1996, 1997, 1998, 1999
  • Camaro Z28 5.7L
    • 1996, 1997
  • Caprice Classic 4.3L, 5.7L
    • 1996

Chevrolet Vehicles:

  • Corvette 5.7L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Express 1500, 2500, 3500 4.3L, 5.0L, 5.7L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
  • Impala 5.7L
    • 1996

Chevrolet Vehicles:

  • S10 Pick Up 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
  • Tahoe 5.7L
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • Sierra, Suburban C1500, C2500, C3500 5.7L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006

GMC Vehicles:

  • Jimmy 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Envoy 4.3L
    • 1998, 1999, 2000, 2001
  • Safari 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

GMC Vehicles:

  • Savana 1500, 2500, 3500 4.3L, 5.0L, 5.7L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
  • Sonoma 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003

Isuzu Vehicles:

  • Hombre 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001

Oldsmobile Vehicles:

  • Bravada 4.3L
    • 1996, 1997, 1998, 1999, 2000, 2001

Pontiac Vehicles:

  • Firebird (Formula and Trans Am) 5.7L
    • 1996, 1997