P2122 OBD-II Trouble Code: Throttle Position Sensor/Switch A Circuit Low Input

P2122 trouble code definition

The P2122 OBD-II trouble, or fault, code means that the vehicle’s on-board computer has detected low voltage in the throttle position sensor (TPS), which is usually below 0.17 volts.

What the P2122 code means

The registration of the P2122 trouble code simply means that low voltage has been detected in the TPS. Depending on the vehicle’s make and model, this detection may trigger a forced engine shutdown, forced idle, or forced reduction in power output to prevent overloading circuitry.

What causes the P2122 code?

While there are multiple potential causes for the P2122 fault code registering, one of four components is likely defective - the throttle position sensor, the throttle actuator control motor, the throttle position actuator, or the pedal position sensor. If all four of these parts are in good working condition, the cause may lie in damaged wiring, connectors, or grounds.

What are the symptoms of the P2122 code?

While the most obvious symptom of the P2122 code is the illumination of the Check Engine Light on the dashboard, the following symptoms may also be noticeable:

• Black smoke upon engine startup
• Labored acceleration
• Misfiring
• No-start condition
• Stalling

How does a mechanic diagnose the P2122 code?

To begin diagnosing the cause of the P2122 trouble code, first verify its existence. A qualified technician can do this through the use of a specialized scan tool that collects data about the vehicle’s performance and reports any anomalies in the form of OBD-II trouble codes. Once a mechanic has performed a scan and the P2122 code registers, then further tests and/or inspections are necessary to narrow down potential culprits.

The next step is often a visual inspection of all wiring and connectors; if damaged wires or connectors are found, they are replaced. The mechanic then clears the trouble code from the computer’s memory and uses the specialized scan tool again. If the P2122 code does not register, the issue is likely resolved. On the other hand, if the code registers again, additional diagnostic efforts are needed.

Using a digital volt/ohmmeter, a mechanic can then check the voltage readings through the throttle position sensor, the throttle actuator control motor, the throttle position actuator, and the pedal position sensor. This will help determine if any of these components is responsible for the low voltage detected by the on-board computer, so faulty parts can be replaced. A technician can also check the voltage through wiring, grounds, and the CAN bus network in order to repair or replace any worn or damaged parts.

Once repairs have been made, the mechanic will clear the OBD-II fault code, scan for anomalies again, and possibly test drive the vehicle to ensure the issue has been satisfactorily resolved.

Common mistakes when diagnosing the P2122 code

Once the P2122 code registers, mechanics sometimes make the following mistakes:

• Failing to address trouble codes in the order of appearance, when multiple codes register
• Failing to verify the existence of the P2122 code
• Failing to clear the P2122 code from the on-board computer following repairs

How serious is the P2122 code?

Although some vehicles do not enter a no-start condition after the P2122 fault code registers, it does not mean the issue that caused it should be ignored. Whether the root cause of the code registering is a faulty component or loose wire or something else entirely, failing to repair the problem has the potential to negatively affect other parts or systems. This ultimately can incur greater cost and hassle in repairs than it would in prompt attention to the matter.

What repairs can fix the P2122 code?

Once the registering of the P2122 trouble code is deemed valid with the use of a specialized scan tool, the following action(s) may be necessary:

• Replacing or repositioning a ground wire
• Replacing the wiring and/or connectors in the CAN bus harness or throttle actuator motor
• Replacing the throttle position sensor, the throttle actuator control motor, the throttle position actuator, or the pedal position sensor

Additional comments for consideration regarding the P2122 code

In the diagnosis of the P2122 code, it is possible for the process to take up to several hours. This is due to the potential need for multiple tests with a scan tool or voltage meter, hands-on inspections, and test drives. In being thorough from the start, the chance of other related problems cropping up is greatly reduced.

Need help with a P2122 code?

If you would like help in diagnosing and addressing the P2122 OBD-II fault code, reach out to YourMechanic to be connected with a qualified technician. This diagnostic and repair professional can even come to your home or office for your convenience or safety. Book an appointment online, get a quote for the cost of repairs, or discuss the possibilities with a representative at 1-800-701-6230.