Throttle Position Sensor
A vehicle that hesitates or stumbles during acceleration, idles intermittently, and performs roughly can have a faulty throttle position sensor (TPS), but these symptoms can also indicate other issues with the vehicle. So before you decide to have your TPS replaced, you'd better troubleshoot the problem first. You need not hire a mechanic to do this. All you need is a working voltmeter, and you can troubleshoot TPS problems all by yourself.
Before you start with your DIY task, you have to prop up the hood first and find the TPS inside the engine compartment. It is usually situated on the outer part, either to the right or left of the throttle body. It looks like a small, black box with an electrical connector where you can see three protruding wires. Now that you've found the TPS, here are the ways to troubleshoot it:
What you'll need:
- Two pins
- Alligator clips
Checking for an open or short in the supply wire
Step 1: Disconnect the electrical connector from the TPS.
Step 2: Turn the ignition switch on without starting the engine. With a voltmeter, check the connector's terminals from the computer side to find out if there's supply voltage.
Step 3: Connect the negative lead (black wire) to the connector's terminal ground and the voltmeter's positive lead (red wire) to the terminal reference voltage wire (gray or blue wire) of the connector. Take note of the meter's findings. It should record a steady 5.0 volts at the terminal. If the meter doesn't display such voltage reading, check the supply wire as there might be an open or short in it.
Step 4: Switch off the ignition and reconnect the sensor's electrical connector.
Testing the throttle position sensor for signal voltage to the computer
Step 1: Get the two pins. Insert one through the ground wire and the other one through the signal voltage wire.
Step 2: With alligator clips, connect the pins to the voltmeter probes.
Step 3: Start the engine and manually open and close the throttle plate while watching the meter's voltage reading. You should observe a gradual voltage increase from 1 to 5 volts then back to 1 volt. If the movement of the voltage signals seems erratic or you think there's no movement at all, then your throttle position sensor now needs a replacement.
Step 4: Turn the engine off.
Testing the sensor's resistance (for TPS with variable resistor)
Step 1: To test a throttle position sensor with a variable resistor, you need to first disconnect the sensor's electrical connection.
Step 2: Get your voltmeter, set it to ohms, and attach the ohmmeter probes to the supply and signal wire contacts of the sensor.
Step 3: Open and close the throttle plate manually while observing the meter's resistance reading. There should be a gradual increase and decrease in the resistance as the throttle plate opens and closes. Erratic resistance movement, no change in resistance, or no resistance at all indicates a faulty TPS.
Adjusting the throttle position sensor
Step 1: Sometimes, the sensor simply needs adjustment to function well. To do that, you need to deal with a number of screws that hold the sensor in place.
Step 2: Loosen each mounting screw. Connect the probes of the ohmmeter to the supply and signal wire contacts of the sensor, and open and close the throttle manually.
Step 3: Rotate the sensor gradually, checking its resistance every time you turn it until you obtain the manufacturer's recommended resistance that's stated in the vehicle's manual.