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Vehicle engine and/or automatic transmission

Code: P0123 - The sensor that measures throttle or pedal position (TPS) is reporting a higher than normal voltage, which may affect acceleration response.

When you see P0123 pop up, what’s really going on is your car’s computer is getting a throttle position signal that’s off the charts-way higher than it should ever be. In my experience, this usually points to the throttle position sensor (TPS) acting up, or sometimes it’s the pedal position sensor misbehaving, especially on newer drive-by-wire systems. That TPS is a little workhorse, living right on the throttle body, and it constantly tells the engine computer exactly how far you’ve got the throttle open. That info’s vital-your fuel and spark depend on it being right. Most electronic throttle cars have two sensors for backup, just in case one fails. If the computer sees that the reading from sensor ‘A’ is too high for a set amount of time, it’ll store this code. And depending on your setup, a similar problem with the accelerator pedal sensor can also trigger P0123. I’ve seen this on a wide range of vehicles, so no brand is immune.

Causes of P0123 trouble code

From my time under the hood, here’s what usually trips a p0123 code:

The throttle position sensor (TPS) going bad-by far, this is the top culprit I see.
A faulty accelerator pedal position (APP) sensor-less common, but worth checking, especially if you’ve got a newer ride.
Problems in the wiring-loose plugs, frayed wires, or a short to voltage anywhere in the TPS or APP circuit. Pro-tip from the garage: always check the wiring before you start swapping sensors.
A throttle body that’s dirty or sticking-a sticky throttle plate from carbon buildup can throw the sensor readings way off.
PCM (engine computer) gremlins-rare, but every now and then a PCM update or replacement is what’s needed.

Honestly, nine times out of ten, it’s a simple wiring fault or a bad sensor. But you can’t skip steps-methodical checking is the only way to be sure. And yes, I’ve run into this on Fords, Chevrolets, Dodges, Toyotas-you name it.

Symptoms of obd code P0123

If you’ve got P0123, the check engine light is almost guaranteed to light up. But from what I’ve seen, you might also notice:

Stumbling or hesitation when you hit the gas pedal.
Rough idling or even the engine stalling, especially when you’re at a stop.
Hard starting or the car just feeling gutless and sluggish.

These problems can come and go, but if you ignore them, trust me-things can spiral fast.

Diagnosis steps for obd2 code P0123

Here’s how I tackle a p0123 code, step by step:

First, check the basics: Make sure your battery’s healthy and the connectors at the throttle body and pedal are firmly clicked in. You’d be surprised how often a loose plug is the only issue.
Look over the wiring harness going to both the throttle and pedal sensors. Keep an eye out for any signs of rubbing, corrosion, or busted wires. Pay extra attention to spots near hot exhaust pieces or moving parts-those areas get chewed up fast.
With the key off, unplug the TPS and check for bent pins or moisture inside the connector. Give it a good cleaning if needed-it only takes a second and can save you a headache.
Grab a scan tool, fire up the live data, and watch the throttle position sensor’s readings. At rest, you want to see something under 1 volt; as you slowly push the throttle, it should rise smoothly to about 4.5 volts. If the number’s stuck high or jumps crazily, you’ve found your problem.
If you’ve got a multimeter handy, back-probe the TPS signal wire and see if the voltage matches what the scan tool shows. Reading pegged over 4.5 volts with the key on and engine off? You might have a short to voltage or a bad sensor on your hands.
Pop off the intake tube and check for carbon gunk or dirt in the throttle body. A sticky throttle plate can mess with readings. Clean it out with throttle body cleaner and a soft rag-don’t go overboard, just enough to get the grime off.
If you’ve checked all this and the problem keeps coming back, then-and only then-start thinking PCM issues or software updates. In my experience, that’s pretty rare.

Here’s a tip: when you’re checking the pedal sensor, have a buddy press the pedal while you watch the scan tool. Makes life a lot easier.

Common Mistakes when fixing P0123

A classic mistake I see is folks rushing to replace the throttle position sensor without even looking at the wiring or connectors. That’s a fast track to wasting money. I’ve also seen people forget about the pedal position sensor or skip cleaning the throttle body, which can be the root cause. And don’t forget to check for technical service bulletins (TSBs) for your specific car-sometimes the automaker’s already got a fix or a software update. Skip these basics, and you’re likely to end up chasing your tail and doing the job twice.

How serious is the P0123 engine code

Let me be blunt-don’t ignore this one. If your throttle or pedal sensor is acting up, your engine can start running rough, hesitate, or even stall out in the middle of traffic. That’s not just annoying-it’s downright dangerous. Leave it long enough, and you could foul your spark plugs, damage the catalytic converter, or even confuse the transmission if the computer’s getting bad info. Bottom line: get it fixed quick, before a small problem turns into a big, expensive headache.

How to repair dtc P0123

Here’s how I’ve fixed dtc p0123 ford, dtc p0123 chevrolet, dtc p0123 dodge, and dtc p0123 toyota more times than I can count:

Swap out that bad throttle position sensor or pedal sensor with a new OEM-quality replacement-don’t skimp on junk parts.
Patch up or replace any damaged wiring or wonky connectors in the sensor circuit.
Give the throttle body a thorough cleaning and make sure the throttle plate isn’t hanging up or sticking.
Secure any sensors that are loose or not mounted right-it only takes a minute and can save a ton of trouble.
If you’ve checked everything and the code keeps coming back, look into PCM updates, or in rare cases, PCM replacement if it’s truly shot.

My advice? Start with the easy stuff-wiring, connectors, cleaning-before tossing money at new sensors. You’d be shocked how many problems come down to something simple.

Conclusion

Bottom line, P0123 means your computer’s getting a throttle or pedal signal that’s way too high, and that can make your car run rough, hesitate, or even stall. It’s a high-priority issue-both for safety and for your engine’s health. Your best bet is to work through the basics: check the wiring, clean everything up, inspect connectors, and only then move on to replacing sensors. Don’t drag your feet on this one. Fixing it quickly is the surest way to keep your car safe, reliable, and running like it should.

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