What Does P0402 Mean?
The Exhaust Gas Recirculation (EGR) system is flowing too much exhaust gas into the intake manifold, or the ECM is detecting excessive EGR flow based on sensor feedback. Note: despite the official description matching P0401 in many databases, P0402 specifically refers to excessive EGR flow. The driver may notice rough idle, stalling, surging, or a noticeable decrease in engine performance, especially at idle or low speeds.
Common Causes
35%
EGR valve stuck partially or fully open due to carbon buildup on the pintle
25%
Faulty DPFE/EGR feedback sensor reporting incorrect pressure differential
20%
EGR vacuum control solenoid stuck open or leaking vacuum to the EGR valve
12%
EGR valve diaphragm or actuator failing to close completely
8%
Plugged or damaged DPFE feedback hoses giving false readings
Diagnostic Steps
1
At idle, monitor the EGR position or DPFE sensor PIDs — the EGR should be commanded closed with near-zero flow. If the sensor shows flow while the EGR is commanded off, the valve is stuck open or the sensor is faulty.
2
With the engine off, remove the EGR valve and inspect the pintle and seat for carbon deposits preventing full closure. The valve should close fully with a tight seal against the seat.
3
Test the DPFE/feedback sensor by disconnecting the feedback hoses — voltage should read approximately 0.45V (varies by manufacturer). If reading is already high with hoses disconnected, the sensor has failed.
4
Check the EGR vacuum solenoid with a multimeter (typical resistance 20–40 ohms) and verify it holds vacuum when de-energized and releases when energized.
5
If the valve appears stuck, try cleaning it with carburetor cleaner and a brush. If the pintle is pitted or the seat is damaged, replace the EGR valve.
Estimated Repair Cost
$120 - $450
Parts + labor, varies by vehicle and location
The Exhaust Gas Recirculation (EGR) system is flowing too much exhaust gas into the intake manifold, or the ECM is detecting excessive EGR flow based on sensor feedback. Note: despite the official description matching P0401 in many databases, P0402 specifically refers to excessive EGR flow. The driv...
The most common cause of P0402 (Exhaust Gas Recirculation Flow Insufficient Detected) is: EGR valve stuck partially or fully open due to carbon buildup on the pintle
Typical repair costs for P0402 range from $120 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Excessive EGR flow can cause the engine to run very rough, stall at idle, or hesitate severely. If stalling occurs in traffic, this becomes a safety concern. Have it repaired soon. The vehicle may fail emissions testing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0402 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control / EGR System
Difficulty
Type
Generic (SAE)
Recommended Tools
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