Emission controls · Powertrain · generic (SAE-defined)
P0402: Exhaust Gas Recirculation Flow Excessive Detected
P0402 means the engine computer detected more exhaust gas recirculation (EGR) flow than it commanded, often because the EGR valve is stuck partly open.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0402 sets
The powertrain control module (PCM) compares the amount of EGR flow it expects, based on its command, with what it infers from manifold pressure, EGR position, or a differential pressure sensor. If flow appears when the valve should be closed, or flow is higher than commanded, the PCM sets P0402. The exact limits are manufacturer-specific.
Common causes of P0402
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- EGR valve stuck open by carbon on the valve seat
- Faulty EGR vacuum solenoid supplying constant vacuum
- Faulty EGR position or differential pressure feedback sensor reading high
- Misrouted vacuum hoses
- Wiring short in the EGR control circuit holding the valve open
P0402 symptoms
- Check engine light on
- Rough or unstable idle
- Stalling when coming to a stop
- Hesitation or stumbling on acceleration
- Hard starting in some cases
How P0402 is diagnosed
- Record freeze frame data and check for other EGR or sensor codes
- Inspect vacuum hose routing against the underhood emissions diagram
- At idle, check whether the EGR valve is open when it should be closed; disconnecting vacuum (on vacuum valves) and noting an idle improvement points to the control side
- Watch EGR position or feedback sensor values in live data with the valve commanded closed
- Remove the valve and inspect the pintle and seat for carbon holding it open
- Test the control solenoid and circuit for a short to ground or constant activation
Typical fixes for P0402
- Clean or replace a stuck-open EGR valve
- Replace the EGR control solenoid
- Replace a faulty EGR feedback sensor
- Correct vacuum hose routing or repair shorted wiring
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Definitions can vary by manufacturer; check factory service information. Ford DPFE-equipped engines are commonly reported to set P0402 from a failed DPFE sensor.
Related codes & warning lights
P0402 FAQ
What does code P0402 mean?
P0402 means the engine computer detected more exhaust gas recirculation (EGR) flow than it commanded, often because the EGR valve is stuck partly open. The standard definition is "Exhaust Gas Recirculation Flow Excessive Detected."
Can I drive with a P0402 code?
Short trips are usually possible, but excessive EGR can cause rough idle, hesitation, and stalling at stops, which can be a safety concern in traffic. Diagnose it promptly.
Why would too much EGR make the engine stall?
Exhaust gas displaces fresh air and oxygen. At idle the engine has little airflow to spare, so extra exhaust dilutes the mixture enough to cause misfiring, rough running, or stalling.
Could a bad sensor alone set P0402?
Yes. If the EGR position or pressure feedback sensor reads high, the computer may report excessive flow even though the valve is working correctly.
Keep researching
More emission controls codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.