Testing the throttle position sensor (TPS) on your 2.4L SOHC equipped Mitsubishi car (or Chrysler Sebring or Dodge Stratus) can be done in three easy steps with a simple multimeter.
You don't need a scan tool to do it and this article will walk you thru' the entire diagnostic and troubleshooting process.
You'll be able to confidently conclude, at the end of the TPS test, that the throttle position sensor is either good or BAD.
If you're wondering if this tutorial applies to your specific Mitsubishi (or Chrysler/Dodge) vehicle, you'll find a complete list of Mitsubishi, Chrysler and Dodge vehicles this tutorial applies to in the box titled ‘Applies To’ on the right-hand column.
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (2.4L Mitsubishi) (at: autotecnico-online.com).
Symptoms Of A BAD Mitsubishi TPS Sensor
Usually you'll experience several things at once when the TPS goes BAD on your Mitsubishi vehicle (or Chrysler Sebring or Dodge Stratus). Along with the CHECK ENGINE LIGHT being ‘on’ on your instrument cluster, you'll also notice one or several of the following:
- TPS diagnostic trouble codes (DTCs) stored in the vehicle's computer's memory.
- P0121: Throttle position sensor circuit range/performance problem.
- P0122: Throttle position sensor circuit low input.
- P0123: Throttle position sensor circuit high input.
- Really BAD gas mileage.
- Transmission does not shift out of second gear.
- No power as you accelerate the vehicle.
- Hesitation when you step on the accelerator pedal.
What Tools Do I Need?
As mentioned at the beginning of the article, you don't need an automotive scan tool to diagnose and troubleshoot the TPS on your Mitsubishi car. You do need:
- A multimeter. It can be digital or an analog one although I recommend a digital multimeter (don't have a digital multimeter? Need to buy one? Click here to see my recommendations: Buying A Digital Multimeter For Automotive Diagnostic Testing).
- A helper to help you with TEST 3.
- A repair manual for any remove and replace info that I don't include in this article.
Circuit Descriptions Of The 2.4L (SOHC) Mitsubishi TPS
This throttle position sensor is a three wire sensor. One wire gets power, another Ground and the other is the throttle position output signal wire. Below are the specifics of each in conjunction with the photo in the image viewer on the right:
- Circuit labeled 1:
- Power Circuit (5 Volts from PCM).
- Circuit labeled 2:
- Throttle Position (TP) Signal Circuit.
- Circuit labeled 3:
- Ground Circuit (Provided by PCM internally).
I'm gonna' make one very important recommendation to you when testing the signals of each wire. And that is to not probe the front of the female terminal of the TPS connector. It's best to use a tool like a back probe or a wire piercing probe on the connector. You can see an example of this tool here: Wire Piercing Probe.
One last observation: these three circuits go directly to the PCM. So you need to be careful not to short the Ground wire to battery power (12 Volts) or you'll fry the PCM.
How Does The Mitsubishi TPS Work?
Here's some very basic working theory that'll make it easier to understand the logic behind the three tests you're about to do. When you turn the key to crank and start your Mitsubishi car (or Chrysler Sebring or Dodge Stratus), this is what happens:
- The PCM (Powertrain Control Module=Fuel Injection Computer) feeds the TPS power (which in this case is 5 Volts DC) and Ground.
- Once the vehicle starts and the engines is idling with the throttle closed.. the throttle position sensor sends the PCM a voltage signal of about .6 Volts DC.
- Once you step on the accelerator pedal and the throttle opens, the TP sensor's voltage signal increases and this is how the PCM knows to dump (inject) more fuel into the cylinders, advance ignition timing, start shifting the automatic transmission, etc.
- As you let go off the gas pedal (accelerator pedal) and the throttle closes, the TP sensor decreases the voltage signal to the PCM, which returns to its base voltage signal, till you step on the accelerator pedal to move the vehicle and the cycle begins again.
Pretty simple stuff, no? Well testing it is just as simple. Since you'll be working in the engine compartment, no need to tell you (but I'm gonna' tell you anyway) to be alert and be very careful. Use common sense and take all necessary safety precautions. OK, let's get this show on the road and go to: TEST 1: Testing The Power (5 Volt) Circuit.