EGR Flow Excessive Detected
The P0402 code indicates that the Powertrain Control Module (PCM) has detected an excessive amount of Exhaust Gas Recirculation (EGR) flow into the intake manifold. This usually happens when the EGR valve is stuck open or the EGR pressure sensor is providing an incorrect reading to the computer.
While not immediately dangerous, excessive EGR flow can cause severe drivability issues like stalling at stops or rough idling. It should be diagnosed soon to prevent engine stalling in traffic.
Common symptoms
- Illuminated Check Engine Light
- Rough idle or engine stalling, especially when coming to a stop
- Hesitation or stumbling upon acceleration
- Decreased fuel economy
- Smell of exhaust gases in the engine bay or cabin
Likely causes
- Stuck open EGR valve due to carbon buildup
- Faulty EGR pressure sensor (DPFE sensor)
- Damaged or disconnected vacuum lines to the EGR valve or sensor
- Faulty EGR vacuum switching valve (VSV) or solenoid
- Wiring or connector issues in the EGR sensor circuit
- Faulty Powertrain Control Module (PCM)
What to check before replacing parts
Scan for other codes and record freeze frame data.
Look for: Check if there are DPFE sensor circuit codes or misfire codes present alongside P0402, which can help isolate the root cause.
Visually inspect the EGR valve, vacuum lines, and DPFE sensor hoses.
Look for: Look for cracked, melted, or disconnected vacuum hoses, as well as damaged wiring harnesses leading to the EGR components.
Test the EGR valve for mechanical operation.
Look for: Apply vacuum to the EGR valve using a hand pump at idle; if the engine does not stumble or stall (or if it won't hold vacuum), the valve may be stuck open or have a ruptured diaphragm.
Inspect the EGR valve for carbon buildup.
Look for: Remove the EGR valve and look for chunks of carbon holding the pintle open, preventing it from seating properly.
Test the EGR pressure sensor (DPFE) voltage.
Look for: Using a multimeter, check the sensor's signal voltage with the key on, engine off, and while running; compare the readings to the manufacturer's specifications to see if the sensor is skewed.
This page explains the generic P0402 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.