Understanding P0402: Exhaust Gas Recirculation Flow Insufficient Detected

What is P0402 Code in Vehicles?

The P0402 diagnostic trouble code is a universal code that’s related to the Exhaust Gas Recirculation (EGR) system in vehicles. The engine control unit (ECU) throws this code when it detects an issue with the EGR system, particularly when the EGR flow is excessive or insufficient.

Importance of Exhaust Gas Recirculation (EGR) System

EGR is an integral part of the vehicle’s emission control system. The EGR system functions to reduce nitrogen oxide emissions, which are harmful pollutants.

Role of EGR Valve

The EGR valve plays a crucial role in controlling the flow of exhaust gases entering the intake manifold. An optimal flow ensures a balanced mix of exhaust gases and air, aiding efficient combustion and minimizing harmful emissions.

What Causes the P0402 Code?

The P0402 code signifies an insufficient EGR flow. It can be caused by various factors.

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Faulty EGR Valve

The EGR valve can become faulty over time. This can disrupt the EGR flow, causing the P0402 code.

Clogged EGR Passages

The EGR passages can get clogged due to carbon build-up, which restricts the EGR flow.

Faulty EGR Control Solenoid

The EGR control solenoid controls the flow of the vacuum to the EGR valve. If it’s faulty, it can cause an insufficient EGR flow.

Problems Associated with Code P0402

The P0402 code can lead to poor vehicle performance. This includes decreased fuel efficiency, engine performance issues, and increased emissions.

How to Diagnose and Fix the P0402 Code

Fixing the P0402 code involves diagnosing the issue and carrying out necessary repairs.


The first step in fixing the P0402 code involves checking the EGR valve, EGR passages, and EGR control solenoid for faults.

Repairing or Replacing Faulty Parts

After diagnosing the problem, the faulty components should be repaired or replaced. This may include cleaning clogged EGR passages or replacing a faulty EGR valve.

Clearing the Code

After the repairs, the P0402 code should be cleared from the ECU. If the code doesn’t reappear after driving, it indicates the problem is fixed.

The Cost of Fixing P0402 Code

The cost of resolving the P0402 code can vary. It depends on the severity of the problem and the parts that need to be replaced. For instance, replacing the EGR valve can cost around $150 to $250, including labor.

Prevention is Better Than Cure: Maintaining the EGR System

Regular maintenance of the EGR system can help prevent the P0402 code.

Regular Check-ups

Regularly inspecting the EGR system can help spot problems early. This includes checking the EGR valve and EGR passages for faults.

Regular Cleaning

Cleaning the EGR system can prevent the build-up of carbon deposits, which can clog the EGR passages and disrupt the EGR flow.


Understanding the P0402 code is crucial for maintaining your vehicle’s performance and emission control. Regular maintenance of the EGR system, along with early diagnosis and repair of issues, can help prevent this code and ensure a smooth ride.

Frequently Asked Questions

What does the P0402 code mean?

  1. The P0402 code indicates that there’s an insufficient exhaust gas recirculation flow in your vehicle.

What are the symptoms of the P0402 code?

  1. Symptoms may include poor engine performance, decreased fuel efficiency, and higher emissions.

Can I drive my car with the P0402 code?

  1. While it might not stop your car from running, driving with an active P0402 code isn’t recommended as it could lead to more significant engine problems.

How is the P0402 code fixed?

  1. Fixing the P0402 code typically involves diagnosing the issue, repairing or replacing faulty components, and clearing the code.

How can I prevent the P0402 code?

  1. Regular check-ups and cleaning of the EGR system can help prevent the P0402 code.