AutoCodes – GMC – P2123 GMC

P2123 GMC Code - Accelerator Pedal Position Sensor 1 Circuit High Voltage

Quick Answer

The Accelerator Pedal Assembly contains 2 Accelerator Pedal Position (APP) sensors. Common causes include Faulty Accelerator Pedal Position Sensor, Accelerator Pedal Position Sensor harness is open or shorted, Accelerator Pedal Position Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P2123 GMC indicates Accelerator Pedal Position Sensor 1 Circuit High Voltage.
Common causes: Common causes include Faulty Accelerator Pedal Position Sensor, Accelerator Pedal Position Sensor harness is open or shorted, Accelerator Pedal Position Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 5,625

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 08, 2022

Description
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
Comments
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Code P2123 GMC Description

The Accelerator Pedal Assembly contains 2 Accelerator Pedal Position (APP) sensors. The APP sensors are mounted to the accelerator pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to the pedal position. The Engine Control Module (ECM) supplies each APP sensor with a 5 V reference circuit, a low reference circuit, and a signal circuit.
Both the APP sensors 1 and 2 signal percentages increase as the pedal is depressed, from approximately 0 percent at rest to above 95 percent when fully depressed.
The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the APP sensor 1 voltage is greater than 4.75 V for less than 1 s.

OBDII Code P2123 GMC - Accelerator Pedal Position Sensor 1 Circuit High Voltage - AutoCodes.com — P2123 GMC Code - Accelerator Pedal Position Sensor 1 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P2123 GMC?

Faulty Accelerator Pedal Position Sensor
Accelerator Pedal Position Sensor harness is open or shorted
Accelerator Pedal Position Sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P2123 GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

User Submitted Video

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P2123 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P2123 GMC code?

Need more information on how to fix the P2123 GMC code? Get Access to Factory Service Manuals

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Information for Specific GMC Models

P2123 2014 GMC Sierra — Accelerator Pedal Position Sensor 1 Circuit High Voltage
P2123 2015 GMC Sierra — Accelerator Pedal Position Sensor 1 Circuit High Voltage
P2123 2016 GMC Sierra — Accelerator Pedal Position Sensor 1 Circuit High Voltage
P2123 2017 GMC Sierra — Accelerator Pedal Position Sensor 1 Circuit High Voltage
P2123 2018 GMC Sierra — Accelerator Pedal Position Sensor 1 Circuit High Voltage

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P2123 GMC Code

No Frequently Asked Questions about P2123 GMC Code found.

Discuss the causes and fixes for P2123 GMC OBDII Code

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OBDIITech
Date: April 6, 2018 at 3:35 am

What model and year is your vehicle? what would you like to reset?

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OBDIITech
Date: April 7, 2018 at 1:20 am

Here is the information from the factory service manual:
Description.
The Engine Control module (ECM) learns the idle position of the throttle body to ensure the correct idle operation. Anytime the ECM or the throttle body is replaced, the ECM must learn the idle position. The Engine idle may be unstable or a DTC may set if the idle position is not learned.
Conditions for running the idle learn procedure:
DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0638, P2100, P2101, P2105, P2107, and P2119 are not set.
the Engine speed is less than 40 RPM.
the vehicle speed is 0 KM/h (0 MPH).
the accelerator pedal position is less than 14.9 percent.
the ignition 1 voltage is more than 10 volts.
the Engine coolant temperature is between 5-85°c (41-185°f).
the intake air temperature is between 5-60°c (41-140°f). Idle learn procedure
Important:
ensure the above conditions are MET before proceeding with this procedure.
do not perform this procedure if a throttle position (TP) sensor or other throttle actuator Control (TAC) system DTCs are set other than P2176. The ECM will not perform the idle learn procedure with a DTC set.
Turn off the ignition for 30 seconds.
Turn on the ignition, with the Engine off for 60 seconds.
Turn off the ignition.
Turn on the ignition, with the Engine off.
Clear the DTCs with a scan tool.

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