P0402 - EGR A Flow Excessive Detected
P0402 is a generic powertrain diagnostic trouble code indicating EGR A Flow Excessive Detected. It relates to the Auxiliary Emission Controls system.
DTC Breakdown (SAE J2012)
| System | Powertrain (P) |
| Type | Generic |
| Subsystem | Auxiliary Emission Controls |
| Fault Index | 02 |
| Standard | SAE J2012 / ISO 15031-6 |
What does diagnostic code P0402 mean?
The engine computer logged P0402 after detecting that the Exhaust Gas Recirculation (EGR) system has excessive flow. The EGR system recirculates exhaust gases to lower combustion temperatures under normal driving conditions.
Severity Level & Driveability Details
Severity: Moderate
An EGR system with excessive flow will increase combustion chamber temperatures, potentially causing spark knock and damage to pistons over time.
Common Symptoms of P0402
- Engine knocking or pinging under acceleration due to EGR excessive flow.
- Rough engine idle or engine stumbling related to EGR excessive issues.
- Check engine light illuminated indicating excessive EGR flow.
Typical Causes for P0402
- Heavy carbon buildup clogging the EGR ports and passages.
- Defective EGR valve stuck closed or open causing excessive flow.
- Failing EGR vacuum solenoid or damaged electrical wiring.
- Faulty EGR pressure sensor (DPFE sensor) reporting incorrect feedback.
Diagnostic and Troubleshooting Steps
Inspect the EGR valve and passages for carbon blockages. Apply manual vacuum to the EGR valve at idle; the engine should idle rough or stall if the EGR system operates properly under excessive.
Typical Repairs and Fixes
- Cleaning carbon blockages from the EGR passages and ports.
- Replacing the defective EGR valve causing excessive flow.
- Replacing the EGR vacuum solenoid or control valve.
- Replacing the DPFE pressure sensor.
Sensor Location & Parts Involved
The EGR valve is mounted on the intake manifold or cylinder head.
Clearing Code & Recurrence
Clear the code using an OBD2 scanner to verify the repair is fixed and complete the EGR drive cycle.
Emissions & Smog Inspection Impact
EGR system faults cause incorrect exhaust recycling, raising NOx or CO/HC emissions.
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Related Diagnostic Codes
Sources & References
This diagnostic guide is compiled and verified against the following authority sources:
- EPA emissions guide
- NHTSA service communications
Frequently Asked Questions about P0402
What does the EGR system excessive flow code P0402 mean?
The engine computer logged P0402 after detecting that the Exhaust Gas Recirculation (EGR) system has excessive flow. The EGR system recirculates exhaust gases to lower combustion temperatures under normal driving conditions.
Is it safe to drive with the EGR system excessive flow code P0402 active?
Yes, but address any engine knocking noise immediately.
How much does it cost to repair a EGR system excessive flow code P0402 fault?
Cleaning carbon from EGR ports is $100-$150. A new EGR valve to resolve excessive is $120-$250 plus labor; total fix is $150-$450.
What are the common causes of the EGR system excessive flow code P0402?
Trigger conditions for the EGR system excessive flow code P0402 include: Heavy carbon buildup clogging the EGR ports and passages., Defective EGR valve stuck closed or open causing excessive flow., Failing EGR vacuum solenoid or damaged electrical wiring..
Can I clear the check engine light for EGR system excessive flow code P0402?
Clear the code using an OBD2 scanner to verify the repair is fixed and complete the EGR drive cycle.
Will the EGR system excessive flow code P0402 cause an inspection failure?
EGR system faults cause incorrect exhaust recycling, raising NOx or CO/HC emissions.