AutoCodes – GMC – P124C 2018 GMC Sierra

P124C 2018 GMC Sierra Code - Injector 5 Positive Voltage Control Circuit Shorted to Control Circuit

Quick Answer

The Engine Control Module (ECM) supplies voltage to each fuel injector on the injector high voltage supply circuits. Common causes include Faulty Fuel Injector 5, Fuel Injector 5 harness is open or shorted, Fuel Injector 5 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: P124C 2018 GMC Sierra indicates Injector 5 Positive Voltage Control Circuit Shorted to Control Circuit.
Common causes: Common causes include Faulty Fuel Injector 5, Fuel Injector 5 harness is open or shorted, Fuel Injector 5 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 241

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Aug 12, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P124C 2018 GMC Sierra Description

The Engine Control Module (ECM) supplies voltage to each fuel injector on the injector high voltage supply circuits. The ECM energizes each fuel injector by grounding the high voltage control circuit of the fuel injector. The ECM monitors the status of the injector high voltage supply circuits and the fuel injector high voltage control circuits. When a fuel injector circuit condition is detected by the ECM, the affected fuel injector(s) is disabled. The Diagnostic Trouble Code (DTC) will be set if the ECM detects the injector high control circuit is shorted to the low control circuit for greater than 2 s.

OBDII Code P124C 2018 GMC Sierra - Injector 5 Positive Voltage Control Circuit Shorted to Control Circuit - AutoCodes.com — P124C 2018 GMC Sierra Code - Injector 5 Positive Voltage Control Circuit Shorted to Control Circuit

What does this mean?

What are the Possible Causes of the DTC P124C 2018 GMC Sierra?

Faulty Fuel Injector 5
Fuel Injector 5 harness is open or shorted
Fuel Injector 5 circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P124C 2018 GMC Sierra?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P124C 2018 GMC Sierra 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 P124C 2018 GMC Sierra code?

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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 P124C 2018 GMC Sierra Code

1. What does the OBDII code P124C mean on a 2018 GMC Sierra?

P124C indicates that the Injector 5 Positive Voltage Control Circuit is shorted to the control circuit, causing improper fuel injector operation.

2. What are the common symptoms of code P124C on a 2018 GMC Sierra?

Symptoms may include rough idling, reduced engine performance, poor fuel efficiency, and the Check Engine Light being illuminated.

3. What causes code P124C on a GMC Sierra?

Common causes include damaged wiring or connectors, a short circuit in the injector wiring, a faulty fuel injector, or a malfunctioning engine control module (ECM).

4. Can a bad injector cause code P124C on a GMC Sierra?

Yes, a faulty injector can cause this code if it leads to a short in the control circuit or disrupts voltage flow.

5. How do you diagnose code P124C on a 2018 GMC Sierra?

Diagnosis involves inspecting the wiring and connectors for damage, testing the injector for proper operation, and checking for shorts or continuity in the circuit.

6. Can I drive my GMC Sierra with a P124C code?

Driving with this code is not recommended, as it can lead to engine performance issues and potential damage to other components.

7. How is code P124C fixed on a 2018 GMC Sierra?

Repairs may include repairing or replacing damaged wiring, replacing the faulty injector, or in rare cases, reprogramming or replacing the ECM.

8. How much does it cost to fix code P124C on a GMC Sierra?

Repair costs vary but can range from $150 to $500, depending on whether the issue is a simple wiring repair or requires injector or ECM replacement.

9. Can a weak battery cause P124C on a GMC Sierra?

While unlikely, a weak or failing battery can sometimes cause electrical issues that may impact injector circuits.

10. Does clearing the code P124C fix the problem on a GMC Sierra?

Clearing the code without addressing the root cause will not fix the problem, and the code is likely to return. Proper diagnosis and repair are necessary.