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OBD code information sheet

https://dvireports.com/p0402

Fault codes DVI Reports
P0402

Exhaust gas recirculation flow excessive

Safe to keep driving?Caution / Repair soonArrange diagnosis soon

Arrange diagnosis soon. A limited journey may be reasonable only if the vehicle runs normally without red warnings, abnormal temperature or severe loss of power. Stop safely if serious symptoms develop.

LowCautionCritical
System groupEmissions & exhaustEGRRepair costs

Technical explanation

The ECU reports excessive EGR flow. Check for a valve remaining open, incorrect actuation and unreliable airflow measurement before replacing parts.

Read the full technical explanation

P0402 indicates excessive EGR flow relative to monitored conditions, unlike the insufficient flow of P0401. A valve may remain open, but inaccurate feedback can create a similar impression for the controller. Compare the closing command, valve position and actual airflow or pressure response. Neither the valve nor the flow sensor should be replaced solely because this code is stored.

Symptoms

  • Unstable idle or an engine tending to stall.

  • Hesitation and power loss, particularly with unwanted EGR opening.

  • Engine warning; the symptom may be intermittent.

Top suspects — what to check first

Suggested checking order, not statistical failure rates or a confirmed diagnosis. Priority can change with the engine and associated codes.

  1. EGR valve that does not close

    Check first

    EGR valve sticking or prevented from closing by deposits.

  2. Electric or pneumatic actuation

    Check next

    Vacuum/electrical control maintaining unwanted opening.

  3. Flow or pressure sensor

    Check next

    Flow/pressure feedback sensor or its pipes measuring incorrectly.

Other possible causes

  1. MAF or other monitoring inputs

    Case-dependent

    Incorrect MAF or other monitor inputs, depending on system architecture.

All causes in the technical record

Some causes overlap with the shortlist above; this is not a probability ranking.

  • EGR valve sticking or prevented from closing by deposits.
  • Vacuum/electrical control maintaining unwanted opening.
  • Flow/pressure feedback sensor or its pipes measuring incorrectly.
  • Incorrect MAF or other monitor inputs, depending on system architecture.

How to test — practical steps

Start with simple checks before buying parts. This is not a VIN-specific workshop procedure; keep clear of moving parts, fuel pressure and energized circuits.

  1. 1

    Save codes and idle symptoms

    Save codes and freeze-frame data, noting whether rough running occurs at idle or after warm-up.

  2. 2

    Inspect EGR hoses and connectors

    Inspect control hoses, connectors and sensing ports for damage or incorrect routing.

  3. 3

    Compare closure command and reported flow

    Check position and flow response to a close command in a manufacturer-approved test.

  4. 4

    Distinguish a stuck valve from a control fault

    Distinguish faulty command from mechanical sticking; an electrically functional valve may not seal closed.

Detailed tests / equipment needed (advanced)

Perform only tests for which you have the correct wiring diagram, equipment and training.

Confirm EGR closure with an approved test

You need:Scanner with EGR functionsEngine diagramWorkshop testing

  1. Check position and flow response to a close command in a manufacturer-approved test.
  2. Distinguish faulty command from mechanical sticking; an electrically functional valve may not seal closed.
  3. Assess MAF and flow/pressure-sensor plausibility rather than treating inferred flow as a direct measurement.
  4. After repair verify idle and EGR-monitor operation. Avoid continuing a road test if stalling or power loss affects safety.

What you should see: Results must match the applicable engine-specific test conditions and limits. One reading does not prove a component has failed.

Electrical, fuel, exhaust or timing measurements require suitable equipment and must not be improvised.

Component location sketch

cabin / firewallfront of the carAir filterIntake manifoldCam coverExhaustTurboBatteryEGR valve
Orientation schematic, not the exact location: position and connector differ by engine and generation. Confirm in your vehicle documentation before removing anything.

Technical references for verification

Full technical diagnosis — additional checks

Step-by-step diagnosis

Checks

Work through the steps before replacing parts. Adapt the checks to the manufacturer’s procedure.

  1. Save codes and freeze-frame data, noting whether rough running occurs at idle or after warm-up.

  2. Inspect control hoses, connectors and sensing ports for damage or incorrect routing.

  3. Check position and flow response to a close command in a manufacturer-approved test.

  4. Distinguish faulty command from mechanical sticking; an electrically functional valve may not seal closed.

  5. Assess MAF and flow/pressure-sensor plausibility rather than treating inferred flow as a direct measurement.

  6. After repair verify idle and EGR-monitor operation. Avoid continuing a road test if stalling or power loss affects safety.

Components to check

This list does not confirm failed components and is not a replacement recommendation. Verify the fault cause and vehicle applicability first.

  • EGR valve and closing/sealing surfaces — inspect.
  • Actuator, control valve and hoses — as fitted.
  • EGR/MAF sensors, sensing pipes and wiring — inspect.

Make- and engine-specific notes

Documented configurations, not proven common defects for all makes or engines. Selecting a vehicle narrows the results.

No reviewed engine-specific exception is available for the selected configuration. Use only the general checks and obtain the exact engine procedure.

Notes are diagnostic leads, not proven faults or disassembly instructions. Do not work on brakes, fuel systems or hot components without proper training.

Check the fuses before ordering a part

An OBD code describes a detected condition; it does not tell you which part to replace. Start with the fuse for the affected circuit.

Find the fuse for your vehicleChoose the make and model, then look up the fuse position in the catalogue.

If the fuse is good, carry on like this:

  1. Check the relevant supplies and connectionsWhere the diagnostic procedure calls for electrical checks, verify supply, ground and connectors under the manufacturer’s activation conditions.
  2. Run the specified component testUse the manufacturer’s test for this code and component before deciding it has failed.
  3. Order only after the fault is demonstratedReplace a part only when the prescribed tests identify it as defective.
Check details
  • Identify the circuit and any relevant fuse: Confirm the vehicle, engine, code meaning and stored operating conditions first. A fuse link is a location aid, not evidence that the fuse caused this code. Use the specified type and rating; do not repeatedly replace a fuse that opens.
  • Check the relevant supplies and connections: Use the specified engine state, circuit conditions and expected values. Have live measurements performed by someone qualified. For non-electrical faults, follow the relevant mechanical, fluid, pressure or leak checks instead.
  • Run the specified component test: Do not apply a generic resistance range. Any resistance or continuity test requires a de-energized circuit and an isolated component, with the correct pins and temperature from the procedure. Some components need a different kind of test.
  • Order only after the fault is demonstrated: If results are normal, continue the relevant wiring, control, mechanical or intermittent diagnosis. Check for related faults and verify the repair under the required conditions. A code or a completed checklist alone does not justify replacement.
Fluke · Continuity testing

If the procedure involves airbag/SRS, pretensioners or a high-voltage system, stop DIY testing and use qualified service. Do not probe these circuits with a multimeter.

Vehicle experiences and cases

User-reported cases published after moderation. Approval does not verify the diagnosis; the same code can have different causes.

No experiences have been published for this definition yet. You can be the first to share the checks and outcome.

See all vehicle experiences

Manuals, components and vehicle guides

Find the relevant procedure in the workshop manual for your vehicle. A fault code alone does not identify a failed part, powertrain or exact schematic.

Find workshop manual / diagramComponents to checkRelated issues and checks

Manuals open at their original source. Exact diagram availability depends on the build year, engine and manufacturer access.

System and diagnostic diagrams

Conceptual illustrations of the system; verify the actual configuration and tests in vehicle-specific documentation.

Technical EGR flow diagram connecting exhaust gases, EGR valve, intake manifold and ECU command for P0401 and P0402.

Exhaust gas recirculation / EGR

Simplified exhaust gas routing. Original conceptual diagram, not an exact component location or an OEM repair procedure.

View full-size diagram →

Can I fix it myself?

Once the cause is confirmed, open the job sheet: difficulty, time, tools, parts and steps. Common jobs for P0402:

Clean or replace EGR valve →

How to fix P0402: step-by-step guide

Symptoms, causes, visual inspection, scan-tool or multimeter tests, replacement and clearing the code, with safety warnings.

EGR valve cleaning: symptoms, causes and step-by-step procedure →

Exhaust-gas recirculation

General system guidance · not a confirmed diagnosis

Flow control uses different sensors and actuators across vehicles. Confirm the definition for the installed architecture.

The association is based on the imported description. This information explains the system; it does not confirm a procedure for the exact code, model or engine. Verify applicability in manufacturer documentation.

Checks for this type of system

  1. Compare EGR request with measured response.
  2. Check restrictions, connectors and hoses only where fitted.

Useful diagnostic data, where available

  • EGR position or estimated flow.
  • Air mass and pressure during permitted testing.

Normal values and thresholds vary by vehicle and are not assumed here.

Mistakes to avoid

  • Not every EGR system is vacuum controlled.
  • Cleaning cannot automatically repair an electrical fault.
System-guide sources

References support general principles, not individual verification of every associated code.

Documented vehicle cases

Applicable only to the vehicles and engines specified in each guide.

Continue your research

Links to related systems, warning lights and vehicle examples.

EGR valve cleaning: symptoms, causes and step-by-step procedureCheck Engine light: meaning and urgencyWhat is EGR?What is a DPF?Read the code with an OBD scanner

Similar codes

P0400Caution / Repair soon

General code

EGR A Flow

Emissions & exhaust · EGR

Open sheet
P0401Critical / Stop safely

General code

Exhaust gas recirculation flow insufficient

Emissions & exhaust · EGR

Open sheet
P0403Caution / Repair soon

General code

EGR A Control Circuit/Open

Emissions & exhaust · EGR

Open sheet
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What should be corrected in this sheet? Do not include names, phone numbers, registration plates or VINs.

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