In a nutshell, a trouble code P0122: Throttle Position Sensor Circuit Low Voltage lets you know that the fuel injection computer notices that the throttle position sensor (TPS) is producing a lower than normal voltage.
In this tutorial I'll explain what this trouble code means. Troubleshooting and repairing this trouble code is not hard. I'll explain what's involved in diagnosing and repairing the cause of this P0122 trouble code.
Contents of this tutorial:
APPLIES TO: This tutorial, on the P0122 OBD II trouble code, applies to the following vehicles:
- 2.2L Honda Accord (DX, EX, LX): 1995, 1996, 1997.
- 2.2L Honda Odyssey: 1995, 1996, 1997.
What Does Trouble Code P0122 Mean?
A trouble code P0122: Throttle Position Sensor Circuit Low Voltage lets you know that the throttle position sensor's signal is stuck at a very low voltage when you're stepping on the accelerator pedal (when the voltage should be greater).
To better understand why this is a problem, take a look at the section: What Does The Throttle Position Sensor Do?
Common Symptoms Of A P0122 Trouble Code
Your Honda's fuel injection computer relies on the throttle position sensor to calculate how much fuel to inject into the engine, since it alerts it to changes in the throttle plate angle.
Since the TPS is an important part of the engine management system, when it fails, engine performance will suffer. You'll see one or more of the following symptoms:
- Check engine light illuminated with a TPS trouble code.
- Rough or low idle.
- Very high idle.
- Engine may start and stall.
- Little to no acceleration
What Does The Throttle Position Sensor Do?
The throttle position sensor's job is to report the changes in the throttle plate's angle as it opens/closes.
And as you're probably aware, the accelerator pedal is connected to the throttle plate via an accelerator cable. So when you step on/off the accelerator pedal, the throttle plate opens/closes.
This causes the engine to breathe in more air (like when you step on the accelerator pedal) or causes the engine to breathe in less air (like when you step off the accelerator pedal).
When the throttle plate is closed (for example, you've got your foot off the accelerator pedal), the signal voltage is about 0.4 to 0.9 Volts DC.
Now, as the throttle plate opens, the throttle position sensor signal voltage increases. At wide open throttle (WOT), the TPS signal voltage is around 4.5 Volts.
As the throttle plate closes, the throttle position sensor signal voltage decreases.
As long as the fuel injection computer sees the TPS voltage signal increasing/decreasing, it knows you're stepping ON/OFF the accelerator pedal (and that the TPS is functioning correctly).
What Causes A P0122 Trouble Code?
The most common cause of a P0122 trouble code is a bad throttle position sensor.
Unfortunately, a bad TPS is not the only cause of a P0122 trouble code. Here's a basic list of a few other things that can cause it:
- An open-circuit problem in the TPS signal wire between the TPS and the fuel injection computer.
- An short-circuit problem in the TPS signal wire between the TPS and the fuel injection computer.
- A bad TPS connector.
- Bad fuel injection computer (although very rare).
How To Diagnose And Repair A P0122 Trouble Code
Troubleshooting and repairing a P0122 trouble code involves testing the throttle position sensor.
The TPS test should confirm that the TPS is really stuck producing a single low voltage value as you open/close the throttle plate.
The TPS test should also confirm that the throttle position sensor is getting 5 Volts and Ground from your Honda's fuel injection computer.
You can correctly conclude that the TPS is bad and the cause of the P0122 trouble code if:
- Your test results confirm that the TPS signal voltage DOES NOT increase as you open/close the throttle plate.
- Your test results confirm that the TPS is getting 5 Volts.
- Your test results confirm that the TPS is getting Ground.
Testing the throttle position sensor is not hard, you find the test explained in detail here: How To Test The TPS (1990-1997 2.2L Honda Accord, Odyssey).
Where To Buy The TPS And Save
The following links will help you comparison shop for the throttle position sensor of a known and solid name brand (Dorman):
More 2.2L Honda Accord And Odyssey Tutorials
You can find a complete list of 2.2L Honda Accord and Odyssey tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The MAP Sensor (1994-1997 2.2L Accord, Odyssey, Prelude).
- How To Test The Head Gasket (1992-1997 2.2L Accord, Odyssey, Prelude).
- How To Test The Engine Compression (1992-1997 2.2L Accord, Odyssey, Prelude).
- How Often Should I Replace The Spark Plugs? (2.2L Honda Accord).
If this info really saved the day, buy me a beer!