If the check engine light is shining ‘nice and bright’ due to a throttle position sensor (TPS) trouble code... this tutorial will help you test it with a multimeter (no scan tool required).
The throttle position sensor is probably one of the easiest engine management sensors to test on your 2.5L V6 equipped Dodge (or Plymouth vehicle).
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.
- More 2.5L V6 Chrysler Diagnostic Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1995-1997 2.5L V6 Chrysler) (at: autotecnico-online.com).
Symptoms Of A Bad Throttle Position Sensor
The throttle position sensor's job is to inform the PCM* of the throttle plate's angle as you step on or off the accelerator pedal (since the accelerator pedal is connected to the throttle plate via a cable).
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.
- 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 2.5L 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.
*PCM = Powertrain Control Module. Refers to the fuel injection computer.
TEST 1: Testing The Throttle Position Sensor Voltage Signal
As you're probably already aware the throttle plate angle voltage signal, that the TPS creates, increases as the throttle plate opens and decreases as it closes.
In about 95% of the cases, when the throttle position sensor fails, it simply stops measuring the throttle plate angle. To put it simply, it stays stuck reporting a single voltage value no matter the location of the throttle plate.
You and I can very easily verify this by tapping into the ORG/LT 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/LT 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 2.5L Stratus or Cirrus, 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 2.5L Stratus or Cirrus.
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 getting 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.