AutoCodes – GMC – P0406 2018 GMC Sierra

P0406 2018 GMC Sierra Code - Exhaust Gas Recirculation Position Sensor Circuit High Voltage

Quick Answer

The Engine Control Module (ECM) uses the Exhaust Gas Recirculation (EGR) position sensor to determine the position of the EGR valve. Common causes include Faulty Exhaust Gas Recirculation (EGR) Valve, Exhaust Gas Recirculation Valve harness is open or shorted, Exhaust Gas Recirculation Valve 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: P0406 2018 GMC Sierra indicates Exhaust Gas Recirculation Position Sensor Circuit High Voltage.
Common causes: Common causes include Faulty Exhaust Gas Recirculation (EGR) Valve, Exhaust Gas Recirculation Valve harness is open or shorted, Exhaust Gas Recirculation Valve 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 233

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 20, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0406 2018 GMC Sierra Description

The Engine Control Module (ECM) uses the Exhaust Gas Recirculation (EGR) position sensor to determine the position of the EGR valve. The ECM sends a reference voltage through the 5 V reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent from the sensor to the ECM through the EGR position sensor signal circuit. The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the EGR position sensor voltage is greater than 4.8 V for greater than 5 s.

OBDII Code P0406 2018 GMC Sierra - Exhaust Gas Recirculation Position Sensor Circuit High Voltage - AutoCodes.com — P0406 2018 GMC Sierra Code - Exhaust Gas Recirculation Position Sensor Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0406 2018 GMC Sierra?

Faulty Exhaust Gas Recirculation (EGR) Valve
Exhaust Gas Recirculation Valve harness is open or shorted
Exhaust Gas Recirculation Valve circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0406 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 P0406 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 P0406 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 P0406 2018 GMC Sierra Code

1. What does the OBDII code P0406 mean on a 2018 GMC Sierra?

P0406 indicates an issue with the Exhaust Gas Recirculation (EGR) Position Sensor Circuit, specifically a high voltage reading that is out of the normal range.

2. What are the common symptoms of P0406 on a 2018 GMC Sierra?

Symptoms may include an illuminated check engine light, reduced engine performance, rough idling, increased emissions, and occasional stalling.

3. What causes the P0406 code on a 2018 GMC Sierra?

Common causes include a faulty EGR position sensor, wiring or connector issues, carbon buildup in the EGR valve, or a malfunctioning EGR valve.

4. Can I drive my 2018 GMC Sierra with the P0406 code?

While driving with P0406 is possible, it may lead to reduced performance and increased emissions. Long-term driving with this code could cause further damage to the engine or emissions system.

5. How can the P0406 code be diagnosed on a 2018 GMC Sierra?

Diagnosis involves using an OBDII scanner, inspecting the EGR valve and position sensor, checking for carbon buildup, and testing the wiring and connectors for damage or loose connections.

6. How do I fix the P0406 code on a 2018 GMC Sierra?

Repairs may include cleaning or replacing the EGR valve, replacing a faulty EGR position sensor, repairing damaged wiring, or clearing carbon buildup in the system.

7. How much does it cost to fix the P0406 code on a 2018 GMC Sierra?

Costs vary depending on the repair. Replacing an EGR valve can range from $150â€“$500, while sensor or wiring repairs may cost less. Diagnosis fees may also apply.

8. Can a dirty EGR valve cause the P0406 code?

Yes, carbon buildup in the EGR valve can restrict its movement and cause the position sensor to send incorrect voltage signals.

9. Is replacing the EGR valve always necessary to fix P0406?

Not always. Sometimes cleaning the EGR valve or repairing wiring and connectors can resolve the issue without needing a replacement.

10. How can I prevent the P0406 code on my 2018 GMC Sierra?

Regular maintenance, such as cleaning the EGR valve, using quality fuel, and keeping up with scheduled tune-ups, can help prevent this code from occurring.