The TPS can be tested with a multimeter while it's still on your on car. You don't need to remove it to test it. By the way, even a scan tool is not required to test it (don't get me wrong, having a scan tool is a must for any serious DIY'er but not necessary to use the info in this tutorial).
So, if the check engine light is lit up by one of the following trouble codes: P0121, P0122, or P0123... this tutorial will help you!
The contents of this tutorial at a glance:
- Symptoms of a Bad Throttle Position Sensor.
- TEST 1: Testing the Throttle Position Sensor Voltage Signal.
- TEST 2: Verifying Throttle Position Sensor Has Power.
- TEST 3: Verifying Throttle Position Sensor Has Ground.
- Where to Buy Your Throttle Position Sensor and Save.
Symptoms of a Bad Throttle Position Sensor
As you step on (or off) the accelerator pedal... the throttle plate opens (or closes) to let more air (or less) air into the engine.
It's the throttle position sensor's job to inform the PCM of these changes in the throttle plate angle (position).
With the throttle plate angle info, the PCM can now calculate several things to keep your engine and automatic transmission performing optimally. Among these 'things' are: injecting more/less fuel, advancing/retarding ignition timing, calculating automatic transmission shift points.
When the TPS fails, you'll see one or more of the following symptoms:
- A TPS diagnostic trouble code (DTC) stored in the PCM's memory:
- P0121: Throttle Position (TP) Circuit Performance Problem.
- P0122: Throttle Position (TP) Circuit Low Input.
- P0123: Throttle Position (TP) Circuit High Input.
- Your 2.7L V6 equipped Stratus (Cirrus) fails the smog check (state mandated emissions test).
- Bad gas mileage.
- Hard start and/or extended cranking time (after shut off).
- Black smoke coming out of the tailpipe.
- Hesitation when accelerating your vehicle down the road.
Thankfully, the TPS can be tested without a scan tool and in the next section we'll start with the very first test.
The TPS signal is a DC voltage signal that reacts to the angle of the throttle plate. To be a bit more specific: As the throttle plate opens, the TP signal voltage increases. As the throttle plate returns back to its closed position, the TP signal voltage decreases.
You and I can very easily verify this increase/decrease in the voltage by tapping into the orange with dark blue stripe (ORG/DK BLU) wire, of the TPS electrical connector, with our multimeter.
This is exactly what we're gonna' do in this test section.
NOTE: The throttle position sensor has to remain connected to its connector for this test to work (this is where a wire piercing probe comes in handy to get to the signal inside the wire. To see what one looks like, click here: Wire Piercing Probe Tool.)
OK, let's start:
Place your multimeter in Volts DC mode and with the RED multimeter lead probe the ORG/DK BLU wire of the sensor's connector.
Ground the BLACK multimeter test lead on the battery negative terminal. Have you helper turn the Key On, but don't start the engine (this will power up the TP sensor).
Your multimeter should report a voltage between .2 to .9 Volts DC. If your multimeter doesn't, don't worry about it just yet, continue with the other steps.
Now, slowly open the throttle (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.
For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.
As the throttle opens, the voltage numbers will increase. This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.
Now, slowly close the throttle. As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.
OK, now you'll need someone to help you lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words ‘lightly tap’) as you slowly open and close the throttle and observe the multimeter.
If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.
Repeat step 7 several times to make sure of your multimeter test results.
Let's take a look at your test results:
CASE 1: The throttle angle voltage increased and decreased as you opened and closed the throttle plate. This confirms that the TP sensor, on your 2.7L Chrysler/Dodge is OK and not defective.
CASE 2: The throttle angle voltage DID NOT increase (and/or decrease) as you opened and closed the throttle plate. This tells you that the TPS is bad and causing the TPS trouble code lighting up the check engine light (CEL) on your 2.7L Chrysler/Dodge.
Before you run out and buy it... I'm gonna' suggest that you do two more tests. One is to check that the TPS is getting power. The other is to check that it's ground. To check that the TPS is getting power, go to: TEST 2: Verifying Throttle Position Sensor Has Power.
CASE 3: Multimeter DID NOT register any voltage, this test result doesn't condemn the TP sensor as BAD just yet. Why? Because...
... the TP sensor may be missing either power or ground. So the next step is to check that the TP sensor is getting power, go to TEST 2: Verifying Throttle Position Sensor Has Power.