AutoCodes – GMC – P021B 2017 GMC Sierra

P021B 2017 GMC Sierra Code - Cylinder 8 Injection Timing

Quick Answer

The Engine Control Module (ECM) has the ability to learn injector timing performance. Common causes include Faulty Fuel Injector 8, Fuel Injector 8 harness is open or shorted, Fuel Injector 8 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: P021B 2017 GMC Sierra indicates Cylinder 8 Injection Timing.
Common causes: Common causes include Faulty Fuel Injector 8, Fuel Injector 8 harness is open or shorted, Fuel Injector 8 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 171

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 Mar 22, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P021B 2017 GMC Sierra Description

The Engine Control Module (ECM) has the ability to learn injector timing performance. When the engine is at operating temperature, throttle closed and in deceleration fuel cut-off mode, the ECM will pulse each injector individually and measure the changes in rotational speed of the crankshaft using the input from the crankshaft position sensor. The ECM will run this diagnostic at one fuel rail pressure operating point for each injector. The ECM stores the injector timing value. The Diagnostic Trouble Code (DTC) will be set when the time to build up sufficient current to open the injector is below or above a predetermined threshold.

OBDII Code P021B 2017 GMC Sierra - Cylinder 8 Injection Timing - AutoCodes.com — P021B 2017 GMC Sierra Code - Cylinder 8 Injection Timing

What does this mean?

What are the Possible Causes of the DTC P021B 2017 GMC Sierra?

Faulty Fuel Injector 8
Fuel Injector 8 harness is open or shorted
Fuel Injector 8 circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P021B 2017 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 P021B 2017 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 P021B 2017 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 P021B 2017 GMC Sierra Code

What does OBDII code P021B mean on a 2017 GMC Sierra?

P021B indicates an issue with the injection timing for Cylinder 8, where the engine control module (ECM) has detected a timing issue or irregularity.

What are the common symptoms of code P021B in a 2017 GMC Sierra?

Symptoms may include rough idling, decreased engine performance, reduced fuel efficiency, hesitation during acceleration, or an illuminated check engine light.

What causes the P021B code to appear in a 2017 GMC Sierra?

Common causes include a faulty fuel injector for Cylinder 8, wiring or connector issues, a malfunctioning ECM, or problems with the fuel system, such as low fuel pressure.

Can I drive my 2017 GMC Sierra with the P021B code?

While it may be possible to drive, it is not recommended because the issue can lead to poor engine performance, increased emissions, and potential engine damage if left unresolved.

How is the P021B code diagnosed in a 2017 GMC Sierra?

A mechanic will typically use an OBDII scanner to read the code, inspect the wiring and connectors for Cylinder 8, test the fuel injector, and check the ECM for proper functionality.

How do I fix the P021B code on my 2017 GMC Sierra?

Repairs may include replacing the fuel injector for Cylinder 8, repairing or replacing damaged wiring, cleaning the injector, updating or reprogramming the ECM, or addressing fuel pressure issues.

Can a dirty fuel injector cause the P021B code?

Yes, a dirty or clogged fuel injector for Cylinder 8 can disrupt injection timing and trigger the P021B code.

How much does it cost to fix the P021B code on a 2017 GMC Sierra?

The cost can vary depending on the exact cause, but replacing a fuel injector typically ranges from $150 to $400, including parts and labor.

Could the ECM be the problem for P021B on a 2017 GMC Sierra?

Yes, a malfunctioning ECM could fail to correctly control the injection timing for Cylinder 8 and trigger the P021B code, though this is less common than injector or wiring issues.

Can low fuel pressure cause the P021B code in a 2017 GMC Sierra?

Yes, insufficient fuel pressure can disrupt the injection process and timing, potentially causing the P021B code to appear.