P0123 Code (Symptoms, Causes, and How to Fix)

We depend on our vehicles, but problems inevitably occur. Modern cars identify issues through diagnostic trouble codes like P0123, pointing to throttle position sensor faults.

Read on to learn the common causes of a P0123 code, whether or not you can continue driving, and how to go about fixing it.

P0123 code

What Does Code P0123 Mean?

OBD-II Trouble Code P0123 Description
Throttle/Pedal Position Sensor/Switch "A" Circuit High Input

Diagnostic trouble code P0123 is indicative of an issue within a vehicle’s throttle pedal position circuit. More specifically, this code signifies that a high input condition exists within this particular circuit. However, to better understand this premise, one must first familiarize themselves with the operation of the TPS circuit as a whole.

A vehicle’s throttle position sensor (TPS) detects the relative position of a vehicle’s throttle pedal, allowing an engine’s ECM/PCM to compare this value to those present at the throttle body. An engine’s control software then specifies a certain amount of throttle plate actuation to provide the requested engine output.

The TPS itself operates as a variable resistor, as it manipulates a static 5V reference signal, in relation to an inputed throttle demand. This resisted voltage is provided to a vehicle’s ECM/PCM in the form of anticipated feedback, which is computed in a preset equation. This equation determines the necessary throttle plate response that is to follow.

In the case of DTC P0123, a vehicle’s management software has concluded that feedback from the TPS is incorrect or irrational, pointing to a high input condition. This issue is only resolved by diagnosing and eliminating the source of this high input condition itself.

Related: DTC P0121, DTC P0122, DTC P2135, DTC P2138

Symptoms of Code P0123

Diagnostic trouble code P0123 is often accompanied by a wide range of additional symptoms. Recognizing these symptoms can prove invaluable when attempting to diagnose the issue at hand.

The following are several of the most common symptoms associated with DTC P0123.

Causes of Code P0123

bad throttle body symptoms

Diagnostic trouble code P0123 can be caused by a host of underlying issues, some of which tend to be much more tedious to diagnose than others. However, by understanding these potential issues, one can expedite the course of repair.

The following are several of the most common causes of DTC P0123.

Is Code P0123 Serious?

Generally speaking, diagnostic trouble code P0123 is considered to be rather serious in nature. This is due to the fact that any fault related to a vehicle’s throttle position sensor circuit can prove detrimental to a vehicle’s overall driveability. This, in turn, can pose a number of safety related issues.

Diagnostic trouble code P0123 is known to cause stalling in the most severe of cases, especially when stopped in traffic at a light or intersection. This can be quite hazardous, even resulting in a collision if such a condition were to arise when not fully stopped.

In any event, the root cause of diagnostic trouble code P0123 should be diagnosed and repaired at the first available opportunity. This prevents issues of this nature from becoming even more dire in nature.

If you do not feel comfortable completing such repairs yourself, an appointment should be scheduled with a trusted repair shop as soon as possible.

How to Fix Code P0123

bad throttle position sensor

The following steps should assist you in diagnosing and repairing the root cause of your vehicle’s P0123 Diagnostic trouble code. As always, you should consult a good repair manual for your particular vehicle before conducting any such repairs.

#1 – Check For Additional DTCs

Before beginning the diagnostic process, check for the presence of any additional diagnostic fault codes. Any active codes should be thoroughly diagnosed before proceeding to the next step.

#2 – Inspect TPS Mounting

Begin by inspecting the throttle position sensor itself. The body of an engine’s throttle position sensor should be free from obvious defects, and should be securely mounted in place.

#3 – Inspect TPS Wiring

Next, thoroughly inspect your engine’s throttle position sensor circuit wiring for chafing, pinched spots, or other forms of damage. Any such damage uncovered during inspection should be thoroughly repaired.

Additionally, it is important to inspect any connectors related to this circuit for the presence of corrosion or damaged pins.

#4 – Check For 5V Reference

You will now check for the presence of a full 5V on your TPS’ reference wire with a quality multimeter. Any deviation in this voltage should be investigated by tracing this particular branch of the affected circuit.

#5 – Verify Ground Signal

Next, you will test to ensure that your engine’s TPS sensor is receiving a valid ground signal. This can be done with a multimeter, while consulting a vehicle-specific wiring diagram.

#6 – Test Feedback Voltage

You will now use the same multimeter to check for any irregularities in feedback voltage from the TPS, while having an assistant slowly actuate your vehicle’s throttle pedal.

Any dead spots within the sweep of a TPS sensor’s detectable range requires further investigation. This can be done by checking the resistance of the TPS at its connector.

A thorough inspection of the engine’s throttle body will also be necessitated. If the throttle body itself is not sticking, replacement of the TPS is advised.

Josh Boyd

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