In a nutshell, a P0122: Throttle Position Sensor Circuit Low Voltage lets you know that the throttle position sensor is not behaving according to the pre-programmed parameters stored in the fuel injection computer.
In this tutorial, I'll explain what this trouble code means. I'll also talk about some of the tests you can perform to find its cause and solution.
Contents of this tutorial:
You can find this tutorial in Spanish here: Código P0122 ¿Qué Significa? (1996-1999 3.8L V6 Buick, Chevrolet, Pontiac, Olds) (at: autotecnico-online.com).
APPLIES TO: This tutorial, on the P0122 OBD II trouble code, applies to the following vehicles:
- 3.8L Buick LeSabre: 1996, 1997, 1998, 1999.
- 3.8L Buick Park Avenue: 1996, 1997, 1998, 1999.
- 3.8L Buick Regal: 1996, 1997, 1998, 1999.
- 3.8L Buick Riviera: 1996, 1997, 1998, 1999.
- 3.8L Chevrolet Lumina: 1998, 1999.
- 3.8L Chevrolet Monte Carlo: 1998, 1999.
- 3.8L Oldsmobile 88 (Eighty-Eight): 1996, 1997, 1998, 1999
- 3.8L Oldsmobile 98 (Ninety-Eight): 1996
- 3.8L Oldsmobile Intrigue: 1998, 1999
- 3.8L Oldsmobile LSS: 1996, 1997, 1998, 1999
- 3.8L Oldsmobile Regency: 1997, 1998
- 3.8L Pontiac Bonneville: 1996, 1997, 1998, 1999
- 3.8L Pontiac Grand Prix: 1997, 1998, 1999
What Does Trouble Code P0122 Mean?
A P0122: Throttle Position Sensor Circuit Low Voltage lets you know that the throttle position sensor's signal is stuck at a voltage of less than 0.16 Volts for more than two seconds.
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
The throttle position sensor is a mission-critical component of the fuel injection system.
As such, when it fails, engine performance will suffer. You'll see one or more of the following symptoms:
- 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 inform the fuel injection computer the throttle plate's angle as it opens/closes.
And as you're probably aware, the throttle plate opens/closes as you step ON/OFF the accelerator pedal.
When the throttle plate is at rest (unopened), 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.
Other things that can cause a P0122 trouble code are:
- An open-circuit or 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 resolving a P0122 involves testing the throttle position sensor.
The test involves confirming that the throttle position sensor is stuck at or below 0.16 Volts as you open/close the throttle plate.
Then making sure that the throttle position sensor is getting 5 Volts and Ground from the fuel injection computer.
So, if the TPS signal voltage DOES NOT increase as you open/close the throttle plate and the sensor is getting 5 Volts and Ground, then you can conclude that the sensor is bad and needs to be replaced.
You can find the TPS test explained in detail here: How To Test The GM 3.8L Throttle Position Sensor (TPS).
Where To Buy The TPS And Save
The following links will help you comparison shop for the throttle position sensor:
More 3.8L V6 GM Tutorials
You can find a complete list of 3.8L GM V6 tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The MAF Sensor (GM 3.8L V6 1996-2005).
- How To Test A Does Not Crank Condition -Case Study (GM 3.8L).
- GM 3.8L Ignition Control Module And Crank (3X, 18X) Sensor Test.
- How To Test The Ignition Coil Pack -Misfire Troubleshooting Tests (GM 3.8L).
If this info saved the day, buy me a beer!
