If the throttle position sensor (TPS) fails and stays stuck producing a high voltage signal, the fuel injection computer will set a P0123: Throttle Position Sensor Circuit High Voltage trouble code.
In this tutorial I'll explain what this trouble code means. I'll also explain what's involved in troubleshooting it and the tests you can perform to find its cause and solution.
Contents of this tutorial:
APPLIES TO: This tutorial, on the P0123 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 P0123 Mean?
A P0123: Throttle Position Sensor Circuit High Voltage lets you know that the throttle position sensor's signal voltage is stuck producing a high voltage value when it should be lower.
To be a bit more specific: The TPS reports that the throttle plate is open when the fuel injection computer knows that it is not open.
Take a look at the section: What Does The Throttle Position Sensor Do?
Common Symptoms Of A P0123 Trouble Code
The throttle position sensor is constantly monitored by the fuel injection computer as soon as you start your Honda Accord or Odyssey's engine.
The information the TPS provides the fuel injection computer is critical. As such, when the TPS fails, your vehicle's engine performance will suffer. You'll see one or more of the following symptoms:
- Check engine light is illuminated by a TPS diagnostic 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 plate's angle changes as it opens/closes. The sensor that's tasked with reporting these changes to the fuel injection computer is the throttle position sensor (TPS).
As you're already aware, the throttle plate is connected to the accelerator pedal via an accelerator cable. As you step on/off the accelerator pedal, the throttle plate open/closes.
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.
As you step on the accelerator pedal, the throttle plate opens. This causes the throttle position sensor's signal voltage to increase.
At wide open throttle (WOT), the TPS signal voltage is around 4.5 Volts.
As you release pressure on the accelerator pedal the throttle plate closes. This causes the throttle position sensor's signal voltage to decrease.
As long as engine is running and the TPS voltage signal increases/decreases, your Honda Accord's fuel injection computer knows you're stepping on/off the accelerator pedal (and that the TPS is functioning correctly).
What Causes A P0123 Trouble Code?
The most common cause of a P0123 trouble code is a bad throttle position sensor.
A few other things can cause P0123 trouble code to light up your Accord or Odyssey's check engine light. These are:
- An open-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 P0123 Trouble Code
Troubleshooting and repairing a P0123 trouble code involves testing the throttle position sensor.
Testing the TPS is the only way to confirm that it's stuck producing a single high voltage value as you open/close the throttle plate.
If the TPS test confirms that the voltage is indeed stuck (as you open/close the throttle plate), the next step is to make sure that it is receiving 5 Volts and Ground from the fuel injection computer.
You can conclude that the sensor is bad and needs to be replaced if your tests results confirm that:
- The TPS signal voltage is stuck at a single voltage value when you open/close the throttle plate.
- The TPS is getting 5 Volts DC from the fuel injection computer.
- The TPS is getting Ground from the fuel injection computer.
Testing the throttle position sensor can be done with a multimeter (no scan tool required). I've written a tutorial that'll help you test it. You can find it 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!