P0402 – OBD-II DTC

OBD-II DTC P0402 – Exhaust Gas Recirculation Flow Insufficient Detected

DTC P0402 meaning

DTC P0402 refers to “Exhaust Gas Recirculation Flow Insufficient Detected.” This code indicates that the Engine Control Module (ECM) has detected a problem with the exhaust gas recirculation (EGR) system, specifically that the flow of exhaust gases being recirculated back into the engine is lower than expected. The EGR system is designed to reduce nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust back into the intake manifold, which helps lower combustion temperatures.

DTC P0402 symptoms

Common symptoms associated with DTC P0402 may include:

• Check Engine Light illuminated
• Rough idle or stalling
• Decreased fuel efficiency
• Increased emissions
• Engine knocking or pinging

DTC P0402 causes

Several factors can lead to the P0402 code being triggered, including:

• Clogged EGR passages or valves
• Faulty EGR valve
• Vacuum leaks in the EGR system
• Faulty sensors (such as the Mass Air Flow sensor)
• Wiring issues or poor connections in the EGR circuit

DTC P0402 seriousness

The seriousness of DTC P0402 can vary. While it may not cause immediate engine damage, it can lead to:

• Increased emissions, which can result in failing emissions tests
• Reduced engine performance and fuel efficiency
• Potential long-term damage if left unaddressed

It is advisable to diagnose and repair the issue promptly to maintain vehicle performance and compliance with emissions regulations.

How to diagnose DTC P0402

To diagnose DTC P0402, follow these steps:

1. Use an OBD-II scanner to confirm the P0402 code and check for any additional codes.
2. Inspect the EGR valve and related components for physical damage or blockages.
3. Check for vacuum leaks in the EGR system.
4. Test the EGR valve operation using a multimeter or by applying vacuum to see if it opens and closes properly.
5. Inspect wiring and connectors for corrosion or damage.
6. Check the Mass Air Flow sensor and other related sensors for proper operation.

How to fix DTC P0402 step-by-step instructions

To fix DTC P0402, follow these steps:

1. Clear the DTC using an OBD-II scanner.
2. Inspect and clean the EGR valve and passages to remove any carbon buildup.
3. Replace the EGR valve if it is found to be faulty.
4. Repair any vacuum leaks in the EGR system.
5. Check and repair any damaged wiring or connectors in the EGR circuit.
6. Test the vehicle to ensure the issue is resolved and the check engine light does not reappear.

How to erase DTC P0402

To erase DTC P0402, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear Codes” option on the scanner.
4. Confirm the action to clear the DTC.
5. Disconnect the scanner and start the engine to check if the code returns.

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