Your Chevy Impala throttle body is made up of several components. The throttle sensor in your 3.8 liter V6 Chevy engine is also known as the Impala TPS Sensor. When you depress your Impala gas pedal, the throttle body opens. From there your Impala TPS Sensor is there to read the position or angle of your throttle blade.
The Impala TPS Sensor is a three wire unit, for power, ground and the signal. Signal is sent to your Chevy Impala Powertrain Control Module, and used to calculate the fuel delivery to your V6 engine. Today I’ll be showing you how to test the Impala TPS Sensor in a 2002 3.8 liter Chevy.
The Impala TPS sensor is connected to your throttle body by two screws. While it’s easy to install the throttle sensor must be calibrated before your can clear your check engine code. Once you are done with installing your new sensor you can use the multimeter to complete the calibration.
Symptoms of a failed Impala TPS Sensor
When your throttle sensor goes bad it means it means there’s an issue with the internals of your TPS. This sensor is basically a potentiometer, and as your throttle blade opens the TPS reads the degree and angle of how far the blade moves.
One of the first signs there’s a problem with your Impala throttle sensor is a Check Engine Light. When you’ve got a Check Engine Light is ON, you will need a OBDII scan tool to retrieve your code as well as erase it.
- Bad gas mileage
- Inconsistent throttle response
- Engine revving automatically
- Car won’t start
- Check Engine Light ON
If you have any of these symptoms, you’ll need this How To tutorial to test and replace your Impala TPS Sensor. Next we’ll be testing for the power signal in your 2002 Chevy Impala.
Checking your Impala TPS Sensor for Power
Take your multimeter and switch it to the DC voltage mode. You’ll need to open your 2002 Chevy Impala hood, and trace back your intake piping until you find the throttle body. Your TPS sensor is mounted opposite of the throttle blade, and it’s connected to a three pin engine harness.
Pull up on the TPS tab and disconnect the three pin sensor. Using your multimeter you’ll be measuring for a power signal at PIN 3, this is a GRAY wire. Before measuring the wire for power hop into your Impala and turn your ignition to the “ON” position. To do this put the black lead on the negative terminal of your battery and GENTLY probe the ENGINE harness side of your Impala TPS Sensor connector.
If you have power at PIN 3 using the Impala TPS Sensor wiring diagram above, the next wire to check is PIN 1. This is a BLACK wire and should return a low reference signal or ground signal to your multimeter.
To test the Impala TPS Sensor ground, simply reverse the polarity of your multimeter. Put the red lead to the positive terminal, and GENTLY probe the ENGINE harness side of PIN 1 with the black lead.
Measuring the Impala TPS Sensor Signal
Now that you have confirmed your throttle sensor is getting power and ground signals, the last leg of this tutorial is to check for TPS signal. This signal is the actual wire that goes to your Chevy Powertrain Control Module. It’s also the wire that you will monitor to calibrate and “tune” your replacement throttle sensor.
For this part of the test you’ll need to plug your Impala TPS sensor back in. Once it’s plugged back in, pierce the BLUE wire or the wire at PIN 2. This is the signal wire going to your Chevy PCM.
While the throttle body is at the closed position, you should see between .5-.9 volts of DC power at this wire. Now you can manually open your throttle body by depressing your throttle blade, or have a friend jump in and push down on your gas pedal fully.
Remember that your Impala engine should not be started, but keep your key turned to the “ON” position. If your Impala TPS is good the measurement at the BLUE wire should be between 4.5-4.9 volts with your throttle fully opened.
If your throttle sensor returns any values outside of these parameters, it’s fried and you need a replacement TPS sensor. Have any questions about this How To guide or your Impala TPS Sensor? Leave us a comment below and let us know!