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AutoCodes – GMC – P0622 2015 GMC Sierra

P0622 2015 GMC Sierra Code - Generator F-Terminal Circuit

Quick Answer

The Engine Control Module (ECM) uses the Generator field duty cycle signal circuit, or F-terminal circuit, to monitor the duty cycle of the Generator. Common causes include Battery charge, Faulty Generator, Generator harness is open or shorted. 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
P0622 2015 GMC Sierra indicates Generator F-Terminal Circuit.
Common causes
Common causes include Battery charge, Faulty Generator, Generator harness is open or shorted.
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 308
How popular is this code, among other codes? Low
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Table of contents Created and updated by William Orellana on Jul 15, 2022
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Code P0622 2015 GMC Sierra Description

The Engine Control Module (ECM) uses the Generator field duty cycle signal circuit, or F-terminal circuit, to monitor the duty cycle of the Generator. The Generator field duty cycle signal circuit connects to the high side of the field windings in the generator. A Pulse Width Modulated (PWM) high side driver in the voltage regulator turns the field windings ON and OFF. The ECM uses the PWM signal input to determine the generator load on the engine. This allows the ECM to adjust the idle speed to compensate for high electrical loads. The ECM monitors the status of the generator field duty cycle signal circuit. When the ignition is ON and the engine is OFF, the ECM should detect a duty cycle near 0%. When the engine is running, the duty cycle should be between 5 - 99%. The Diagnostic Trouble Code (DTC) will be set if the ignition is ON, and the engine OFF (Prior to Ignition ON, the ignition must have been OFF for at least 5 s), the ECM detects a PWM signal that is greater than 65% for 5 s.
OBDII Code P0622 2015 GMC Sierra - Generator F-Terminal Circuit - AutoCodes.com
P0622 2015 GMC Sierra Code - Generator F-Terminal Circuit
What does this mean?

What are the Possible Causes of the DTC P0622 2015 GMC Sierra?

  • Battery charge
  • Faulty Generator
  • Generator harness is open or shorted
  • Generator circuit poor electrical connection
  • Faulty Engine Control Module (ECM)

How to Fix the DTC P0622 2015 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 P0622 2015 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 P0622 2015 GMC Sierra code?

Need more information on how to fix the P0622 2015 GMC Sierra code? Get Access to Factory Service Manuals

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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 P0622 2015 GMC Sierra Code

1. What does the OBDII code P0622 mean for a 2015 GMC Sierra?

Code P0622 indicates an issue with the generator F-terminal circuit, which involves the alternator's ability to communicate with the vehicle's control module.

2. What are the common symptoms of code P0622 on a 2015 GMC Sierra?

Symptoms can include a charging system warning light, battery not charging, dim headlights, and difficulty starting the vehicle.

3. What causes the P0622 code on a 2015 GMC Sierra?

Common causes include a faulty alternator, damaged wiring or connectors in the F-terminal circuit, or issues with the powertrain control module (PCM).

4. Can I drive my 2015 GMC Sierra with code P0622?

It’s not recommended to drive with this code active for long periods, as it could lead to battery drain and potential stalling due to loss of electrical power.

5. How do I diagnose the P0622 code on a 2015 GMC Sierra?

Start by inspecting the alternator and F-terminal wiring for damage or corrosion. Use a multimeter to test circuit continuity and check the alternator's output.

6. How is code P0622 fixed on a 2015 GMC Sierra?

Repairs may involve replacing a faulty alternator, repairing or replacing damaged wiring, or reprogramming or replacing the PCM if necessary.

7. How much does it cost to fix code P0622 on a 2015 GMC Sierra?

Costs vary depending on the repair, but alternator replacement typically ranges from $400 to $800, while wiring repairs are usually less expensive.

8. What tools are needed to troubleshoot code P0622 on a 2015 GMC Sierra?

A multimeter, wiring diagram, and an OBDII scanner are essential tools for diagnosing and troubleshooting this code.

9. Can a weak battery trigger code P0622 on a 2015 GMC Sierra?

While a weak battery alone may not cause this code, it can worsen charging system issues and should be tested during diagnosis.

10. Does the P0622 code require reprogramming the PCM on a 2015 GMC Sierra?

Reprogramming the PCM is only necessary if the PCM itself is faulty or if updated software addresses the issue.

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