When you se a P0122: Throttle Position (TP) Circuit Low Input code lighting up the check engine light on your 2000-2007 2.0L Ford Focus, the throttle position sensor (TPS) is sending the PCM a voltage that's too low for the current throttle plate angle.
In this guide, I'll explain what P0122 really means, what typically causes it, and how you can diagnose it and fix it without guesswork —or replacing parts that aren't bad.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 2.0L SOHC Ford Focus: 2000, 2001, 2002, 2003, 2004.
- 2.0L DOHC Ford Focus: 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
TPS MULTIMETER PERFORMANCE TESTS:
OTHER TPS TROUBLE CODES EXPLAINED:
- P0121 TPS Code Diagnostics (2000-2007 2.0L Ford Focus).
- P0123 TPS Code Diagnostics (2000-2007 2.0L Ford Focus).
What Does P0122 Really Mean?
The P0122 DTC doesn't just flag a TPS problem —it tells you exactly how (or why the PCM thinks) it's failing, and that hint is priceless for our diagnostic purpose.
In a nutshell, P0122 means the PCM is reading a throttle-position sensor (TPS) voltage that's stuck too low —typically under 0.17 volts— even though the throttle blade isn't fully shut.
On the 2000–2007 2.0L Ford Focus, the TPS normally outputs somewhere between roughly 0.3 and 4.5 Volts, depending on throttle angle (which, of course, changes with every touch of the gas pedal).
If that reading dips below 0.17 Volts for a set amount of time, the PCM flags the signal as bad and stores the P0122 TPS Voltage Low code.
A voltage that low —or stuck that low— will have the PCM throwing a hissy fit and give you lazy throttle response, boggy acceleration, or hit-and-miss engine behavior (but we'll dive into those symptoms in the next section).
Common Symptoms Of Code P0122
When your Ford Focus logs a P0122 —TPS Voltage Low, you can expect one or more noticeable drivability issues.
Typical symptoms of a TPS voltage signal stuck low include:
- Sluggish or delayed throttle response
- Engine hesitation under acceleration
- Rough idle or stalling as the vehicle comes to a stop
- Harsh or delayed transmission shifts
- Overall reduced engine power
If your Ford Focus' TPS or its circuit is in permanent failure, these symptoms will be constant. With an intermittent sensor or wiring fault, they may appear and disappear. We'll dig further into this behavior in the next section.
Common Causes Of A Code P0122
Like we touched on earlier, a P0122 shows up when the PCM spots a TPS voltage that's stuck too low for the current throttle angle.
Nine times out of ten the sensor itself is at fault, but there are a few other gremlins that can trigger the code on a 2000–2007 2.0L Ford Focus:
- A worn or failing TPS that hasn't completely quit yet.
- No 5-Volt reference getting to the sensor (this is the sensor's power supply voltage).
- A shorted or open TPS signal wire.
- Loose or corroded connector terminals.
- Internal PCM fault (rare).
The only way to know for sure is to check your TPS with a multimeter. With a few quick and easy checks, you can confirm the signal voltage, verify the 5-Volt feed, and make sure it's getting Ground.
I've written a step-by-step guide that walks you through the whole testing process:
In the next section, we'll sort out whether it makes more sense to break out the multimeter and test the TPS —or simply swap in a new one and call it a day.
Should You Replace The TPS?
So far, we've seen that a P0122 —TPS Voltage Low on you 2000-2007 2.0L Ford Focus can stem from a faulty throttle position sensor, but it might just as well be caused by a wiring fault or a missing 5 Volt reference or Ground.
That leaves us with the big question: do we test the TPS, or just swap it out and move on? I'll give you my two cents on it.
Plenty of folks —shops included— skip the diagnostics and simply replace the sensor. Truth be told, that fixes the issue most of the time. The part is inexpensive, easy to access, and a quick change often gets the Focus back on the road with minimal fuss.
If it doesn't solve the problem, it doesn't bother them —they did the job themselves (no shop labor or diagnostic fees, just the price of the sensor), and now they know it's time to dig a little deeper.
If you're leaning that direction, here are a few TPS replacements that fit the 2000–2007 2.0L Ford Focus. They're quality parts from brands I trust —and buying through these links helps support this site without costing you a cent extra:
- A-Premium TPS #5017479AA (at: amazon.com).
- Standard Motor Products TH190T Throttle Position Sensor (at: amazon.com).
That said, there are two solid reasons to check the sensor first:
- The TPS isn't always the culprit. If it's missing its 5-Volt power supply, a solid Ground, or the connector's damaged, swapping the sensor won't solve the underlying issue.
- It's super easy to test. The sensor's right out in the open, and you don't need a scan tool or any fancy (expensive) gear.
With a basic multimeter and a few minutes, you can confirm the TPS signal output, power, and Ground —and know exactly what you're dealing with before shelling out for a new part.
Here's my step-by-step tutorial on checking the TPS signal, 5-Volt reference, and Ground using a multimeter:
More 2.0L Ford Focus Diagnostic Tutorials
You can find a complete list of tutorials and wiring diagrams for the 2.0L Ford Focus in this index:
Here's a small sample of the tutorials you'll find:
If this info saved the day, buy me a beer!
