DTC P0122 – How To Test a Mitsubishi Evolution TPS

DTC P0122 – How To Test a Mitsubishi Evolution TPS


The OBDII trouble code of P0122 is a sign that there’s a problem with your throttle position sensor (TPS) and this DIY How To shows you how to test a Mitsubishi Evolution TPS. Specifically, this check engine light means that your Mitsubishi ECU is not receiving the correct voltage from the throttle position sensor.

As you depress your gas pedal, the cable connected to the other end of the pedal opens your throttle blade. As the blade of the throttle opens, more air is allowed to enter the motor. The ECU uses the signal from your TPS to determine just where the throttle blade is, and how much it’s open. Armed with this knowledge, along with a few other engine inputs, your Evolution ECU can then operate the engine’s spark and fuel events.

Today we’ll be showing you how to test a Mitsubishi Evolution TPS for signal, power and ground to see if it’s operating correctly. We’ll also be showing you how to replace a Mitsubishi Evolution TPS using a 2005 Evolution 8.

The throttle position sensor in your 4G63 equipped Evolution is basically a potentiometer that reads how much the throttle blade is open. Because this part is independent of the throttle body, you can replace the throttle position sensor and calibrate it without having to remove the throttle itself.

What are the possible causes of P0122


If the voltage from your throttle position sensor is too low for your ECU to use, it can cause serious drivability issues. There’s only a handful of possible causes for this DTC, the first of which is that your TPS has somehow come loose.
Your throttle position sensor wiring may also have a short or break in it, and lastly a failed throttle position sensor could also fail to react and work correctly.

How To Test a Mitsubishi Evolution TPS

In order to test your Evolution TPS, you will need a multimeter or voltmeter. If you are not familiar with these tools or are not sure how to use them, check out our primer here.

Step 1 : Locate your 4G63 TPS

Your throttle position sensor is mounted opposite the throttle butterfly, near the BISS screw on your Mitsubishi throttle body. It’s connected by a four pin weatherproof connector, that has just three metal pins in it.
Unplug your throttle position sensor and inspect the terminals inside the connector. You’ll be testing pins using your multimeter to see if your Mitsubishi Evolution TPS is receiving power as well as ground.
As you can see the connector is comprised of four spots but only with three terminals. We’ll label the power and ground terminals below, so that you can work from them accurately. Connect the black lead of the multimeter to your battery and probe PIN C for the switched power signal.
You should have 5 volts of power here with the key inserted in the ignition and turned to the “ON” position. The next wire you’ll be testing is the LR pin, which is the low reference ground signal provided by your 4G63 ECU. The LR pin is the last pin that’s closest to your firewall.
If you have power and ground at your TPS, the last part of learning how to test a Mitsubishi Evolution TPS is to measure the signal wire. This is the actual wire that sends the throttle position to your ECU.
Reconnect the throttle position sensor connector, and you will be backpinning the last remaining pin for the signal wire in question. Do not start your 4G63 engine, but instead have a friend depress the accelerator all the way down. With the throttle blade opened fully, look for a voltage value around 4.5 to 5.0 volts.
Now have your friend close the throttle completely and then slowly and gradually open the throttle. Keep your multimeter connected the entire time so you can see the full sweep of voltage. There should be no spikes or gaps in the voltage as your assistant depresses the gas pedal slowly. If this test comes back okay, your throttle position sensor check engine light may be intermittent.
Clear your OBDII trouble code and see if the P0122 or P0120 returns. If any of these tests do not return results that are similar with our How To Test a Mitsubishi Evolution TPS guide, stop and replace your TPS immediately. The part number for this Mitsubishi part is MD628074.
That does it for our How To Test a Mitsubishi Evolution TPS guide! Have any questions or comments? Leave them for us below!