Enter the error code and car brand

Vehicle engine and/or automatic transmission

Code: P0120 - The throttle or pedal position sensor “A” circuit, which helps control engine power, has a problem.

Let me break down what P0120 means for you. This code stands for “Throttle/Pedal Position Sensor ‘A’ Circuit.” In plain English, your car’s computer (the PCM) is seeing something strange with the voltage readings coming from either the throttle position sensor (TP) or the accelerator pedal position sensor (APP). These sensors are crucial-they tell your engine how much you’re pressing the gas and how open the throttle is, so the car knows how much power you want. If the readings from these sensors don’t match what the computer expects, it sets this code. On modern cars, especially those with electronic throttle control, these sensors are vital for smooth driving and safety. If something’s off, the car might even limit your speed to keep things safe.

Causes of P0120 code

From what I see most often in the shop, P0120 usually comes down to a handful of culprits. Here’s what I recommend checking first:

Faulty throttle position sensor (TP sensor) - This is the most common issue in my experience.
Faulty accelerator pedal position sensor (APP sensor) - Less common, but it does happen.
Damaged or corroded wiring or connectors - Sometimes it’s just a bad connection or a wire that’s frayed or corroded.
Dirty or defective throttle body - A gummed-up throttle body can cause all sorts of weird sensor readings.
PCM (engine computer) issues - Rare, but possible, especially if there’s a software glitch or internal fault.

In cases like this, it’s usually the sensor or the wiring, but I always check everything to be sure. This error can also happen on car brands like Mitsubishi, Opel, and Nissan.

Symptoms of dtc P0120

If you’ve ever had this code rear its head, you already know it’s not just a harmless warning. The check engine light will be glaring at you-that’s your car’s way of saying, “Hey, something’s up.” From my time under the hood, I’ve seen engines stumble, misfire, or even shake like they’ve had too much coffee. Starting the car might become a chore, or you’ll notice it hesitates when you step on the gas. Here’s a big one: on certain vehicles, especially with electronic throttle control, you can get thrown into limp mode-suddenly, your car’s crawling, no matter how hard you press the pedal. That’s the computer taking charge, keeping things safe but also making driving a pain. I’ve seen this happen on dtc p0120 mitsubishi and dtc p0120 opel models quite a bit, all due to how their electronic throttle systems are wired up. Bottom line: if you spot these symptoms, don’t brush them off. They can spiral into bigger headaches in no time.

Diagnosis with P0120 engine code

When I’m chasing down a P0120, I like to be methodical-missing a simple detail can cost you hours. First, I always scan for other codes. Sometimes, P0120 shows up with a crowd, and those extra codes can point you straight to the trouble spot. After that, I pop the hood and go hands-on with the wiring and connectors at both the throttle body and the accelerator pedal. Look for anything loose, green with corrosion, or flat-out broken. Here’s a pro-tip from the garage: gently wiggle the connectors while watching a scan tool or voltmeter. Some faults only show up when things move.

If that looks good, I check the throttle body for carbon gunk. You’d be surprised how often a filthy throttle body trips up the sensors. A quick cleaning with the right spray and a soft brush can work wonders.

Next up, the multimeter comes out. With the key on and engine off, check for that solid 5-volt reference at the sensor. No 5 volts? You might have a wiring issue or a PCM glitch. Then, I slowly work the throttle and watch the sensor’s voltage-it should sweep smoothly. If it jumps, drops out, or sticks, you’ve likely found your culprit.

If you get stumped at the throttle, move to the pedal sensor and repeat those voltage checks. Rarely, the PCM itself is at fault, but I always leave that for last because it’s the least likely and most expensive fix.

One last thing-don’t try to do it all solo. Having a helper press the accelerator while you watch the readings can make life a lot easier. If you’re working on a dtc p0120 nissan, this same routine will have you covered.

Common Mistakes with obd code P0120

A classic mistake I see is folks swapping in a brand-new throttle position sensor right off the bat, hoping it’ll fix everything. But if a corroded connector or a broken wire is the true villain, that new sensor won’t help a bit. Another misstep? Skipping over a dirty throttle body. It doesn’t matter how shiny your new sensor is-if the throttle plate’s gummed up, you’re still chasing your tail. And don’t overlook other codes; sometimes P0120 is just a symptom, not the root cause. My advice? Slow down, go step by step, and double-check the basics before you start throwing parts at the problem. That’s how you save both time and cash.

Seriousness of P0120

Let’s not sugarcoat it: this isn’t the kind of problem you can just leave for another day. A faulty throttle or pedal position sensor will mess with your engine’s performance, cause random stalling or hesitation, and can even put you in harm’s way if the car decides to cut power at the wrong moment. Modern cars with electronic throttle control can slam you into limp mode, which is no fun if you’re trying to merge onto the highway. Ignore it long enough, and you’re risking catalytic converter damage from misfires. I’ve seen folks get stranded or wind up in dangerous situations because they brushed this off. Take it seriously-it’s not worth gambling with your safety.

Repair steps for obd2 code P0120

Once you’ve nailed down the source of the trouble, here’s the playbook I follow in the shop:

If either the TP or APP sensor is faulty, swap it out with the right, vehicle-specific part. Don’t cut corners with generic replacements.
Found wiring that’s banged up or corroded? Fix it properly-solder and heat-shrink are your friends here, not electrical tape.
If the throttle body looks like it’s been through a mudslide, give it a thorough cleaning with the right cleaner and a soft brush until it shines.
If, after all this, you’re faced with a bad PCM (which is pretty rare), you might need to reprogram or replace it, but always exhaust every other option first.

After the repairs, clear the code and take the car for a solid test drive. I like to put the vehicle through a few stop-and-go cycles, just to make sure everything’s back to normal. For dtc p0120, this method works for pretty much any make or model you’re likely to see.

Conclusion

Here’s the bottom line: if your car is throwing a P0120, it’s the computer’s way of telling you there’s a problem with the throttle or pedal position sensors. It’s a critical issue, not just an annoyance, because it can turn a smooth-running engine into a ticking time bomb. In my experience, the fastest path to a real fix is to work through each step-start by inspecting sensors, wiring, and the throttle body, and only replace what’s actually failing. Don’t wait around-get it sorted so you can get back on the road with peace of mind.

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