AutoCodes – GMC – P0402 GMC

P0402 GMC Code - Exhaust Gas Recirculation Flow Excessive

Quick Answer

The Exhaust Gas Recirculation (EGR) valve is controlled by the Engine Control Module (ECM). Common causes include Faulty Exhaust Gas Recirculation (EGR) Valve, EGR solenoid valve harness is open or shorted, EGR solenoid valve circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0402 GMC indicates Exhaust Gas Recirculation Flow Excessive.
Common causes: Common causes include Faulty Exhaust Gas Recirculation (EGR) Valve, EGR solenoid valve harness is open or shorted, EGR solenoid valve circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 1,450

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0402 GMC Description

The Exhaust Gas Recirculation (EGR) valve is controlled by the Engine Control Module (ECM). The ECM controls the EGR valve by supplying a 12-volt pulse width modulated signal to the EGR Valve low control circuit and 12 volts to the high control circuit. The ECM monitors the EGR flow performance when the EGR is active by comparing the desired Mass Air Flow (MAF) to the actual MAF. If the difference between the desired MAF and the actual MAF is less than or greater than a calibrated threshold level the amount of detected EGR flow is out of range. The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the difference between the desired mass air flow and the actual mass air flow is less than a calibrated value for greater than 12.5 s.

OBDII Code P0402 GMC - Exhaust Gas Recirculation Flow Excessive - AutoCodes.com — P0402 GMC Code - Exhaust Gas Recirculation Flow Excessive

What does this mean?

What are the Possible Causes of the DTC P0402 GMC?

Faulty Exhaust Gas Recirculation (EGR) Valve
EGR solenoid valve harness is open or shorted
EGR solenoid valve circuit poor electrical connection

How to Fix the DTC P0402 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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0402 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 P0402 GMC code?

Need more information on how to fix the P0402 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0402 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P0402 2014 GMC Sierra — Exhaust Gas Recirculation Flow Excessive
P0402 2015 GMC Sierra — Exhaust Gas Recirculation Flow Excessive
P0402 2016 GMC Sierra — Exhaust Gas Recirculation Flow Excessive
P0402 2017 GMC Sierra — Exhaust Gas Recirculation Flow Excessive
P0402 2018 GMC Sierra — Exhaust Gas Recirculation Flow Excessive

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 P0402 GMC Code

1. What are the common symptoms of OBDII code P0402 GMC?

The common symptoms of code P0402 GMC include a Check Engine light illumination, rough idling, reduced fuel efficiency, and potentially an increase in emissions.

2. What are the possible causes of OBDII code P0402 GMC?

The excessive Exhaust Gas Recirculation (EGR) flow indicated by code P0402 GMC can be caused by a faulty EGR valve, clogged EGR passages, a malfunctioning EGR temperature sensor, or issues with the EGR vacuum modulator.

3. How can I diagnose the cause of OBDII code P0402 GMC?

To diagnose the cause of code P0402 GMC, it is recommended to perform a visual inspection of the EGR system components, check for vacuum leaks, test the EGR valve functionality, and use a scan tool to monitor EGR system data.

4. Can a dirty or clogged EGR valve trigger code P0402 GMC?

Yes, a dirty or clogged EGR valve can disrupt the proper flow of exhaust gases and trigger code P0402 GMC. Regular maintenance and cleaning of the EGR valve can help prevent this issue.

5. Is it safe to continue driving with OBDII code P0402 GMC present?

While it may be possible to drive with code P0402 GMC present, it is not recommended as the underlying issue causing the excessive EGR flow can lead to further engine problems if left unresolved.

6. How can I repair OBDII code P0402 GMC?

Repairing code P0402 GMC typically involves cleaning or replacing the EGR valve, clearing any blockages in the EGR passages, checking and replacing the EGR temperature sensor if necessary, and ensuring proper operation of the EGR vacuum modulator.

7. Can a malfunctioning EGR temperature sensor cause code P0402 GMC?

Yes, a malfunctioning EGR temperature sensor can cause code P0402 GMC by providing incorrect temperature readings to the engine control module, leading to improper EGR flow calculations.

8. What are some tips to prevent OBDII code P0402 GMC from recurring?

To prevent code P0402 GMC from recurring, it is advisable to regularly inspect and clean the EGR system components, use high-quality fuel to reduce carbon buildup, and address any engine performance issues promptly.

9. Will resetting the Check Engine light resolve OBDII code P0402 GMC?

Resetting the Check Engine light may temporarily clear the code, but it will not fix the underlying issue causing code P0402 GMC. It is important to diagnose and repair the root cause to prevent the code from reappearing.

10. Can a failing EGR vacuum modulator trigger code P0402 GMC?

Yes, a failing EGR vacuum modulator can disrupt the vacuum signal to the EGR valve, leading to improper EGR flow and triggering code P0402 GMC. Inspecting and replacing the EGR vacuum modulator can help resolve this issue.