P0402
Exhaust Gas Recirculation Flow Excessive DetectedP0402 is a generic OBD-II powertrain diagnostic trouble code: Exhaust Gas Recirculation Flow Excessive Detected. It is logged by the engine control unit when the egr monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0402 means
P0402 is a SAE generic OBD-II diagnostic trouble code that indicates the engine control module (ECM/PCM) has detected an excessive amount of exhaust gas being recirculated into the intake manifold via the Exhaust Gas Recirculation (EGR) system. The EGR system is designed to reduce combustion temperatures and nitrogen oxide (NOx) emissions by metering a controlled amount of inert exhaust gas back into the intake charge. When flow exceeds the expected range for a given operating condition, the PCM sets P0402 and illuminates the MIL.
The most frequent root cause is carbon buildup at the EGR valve port or intake manifold passages, which can partially block the valve in an open position and allow exhaust gas to bleed through even at idle. On Ford and some other platforms, a faulty Differential Pressure Feedback EGR (DPFE) sensor is actually the most common trigger — it reports a higher differential pressure than is physically present, leading the PCM to conclude flow is excessive even when the valve is functioning correctly. A stuck-open EGR valve or a leaking vacuum supply line are additional common culprits.
While the vehicle typically remains driveable with P0402 set, the excess inert gas entering the combustion chamber causes rough idle, engine surge, and increased fuel consumption. Prolonged operation can lead to misfires, elevated catalyst temperatures from incomplete combustion, and potential damage to downstream components.
Common causes
Most-frequently reported root causes when P0402 is logged.
-
1
Faulty or drifted DPFE (Differential Pressure Feedback EGR) sensor reporting excessive flow (most common on Ford platforms)
-
2
Carbon buildup blocking the EGR valve in a partially open position
-
3
Stuck-open or mechanically failed EGR valve
-
4
Vacuum line leak causing unintended EGR valve actuation
-
5
Defective or stuck-open EGR solenoid/control valve
-
6
Wiring fault or poor connector contact in the EGR position/feedback circuit
-
7
PCM calibration error or software fault (rare)
Symptoms drivers notice
How to diagnose P0402
A typical diagnostic flow when this code is present.
-
1
Connect a scan tool and confirm P0402 is the only stored code; note any related P040x EGR codes
-
2
Inspect all EGR vacuum lines for cracks, kinks, or loose connections
-
3
On Ford and compatible vehicles, check DPFE sensor output voltage at idle and with EGR commanded open
-
4
Visually inspect the EGR valve and its port into the intake manifold for heavy carbon deposits
-
5
Apply a controlled vacuum source directly to the EGR valve at idle
-
6
Test EGR solenoid resistance and verify PCM-controlled ground switching with a digital multimeter
-
7
Clear codes, perform a drive cycle that exercises EGR operation, and recheck for a returning P0402
Vehicles where we've handled P0402
Platforms in our catalogue with confirmed P0402 coverage.
Related powertrain codes
- P0400 — Exhaust Gas Recirculation Flow Malfunction
- P0401 — Exhaust Gas Recirculation Flow Insufficient Detected
- P0403 — Exhaust Gas Recirculation Circuit Malfunction
- P0404 — Exhaust Gas Recirculation Circuit Range/Performance
- P0405 — Exhaust Gas Recirculation Sensor A Circuit Low
- P0406 — Exhaust Gas Recirculation Sensor A Circuit High
Frequently asked questions
Can I keep driving with a P0402 code?
Yes, the vehicle is generally driveable, but you should address the fault promptly. Excess EGR flow causes rough idle, poor fuel economy, and can eventually trigger misfires or damage the catalytic converter if left uncorrected.
Is the EGR valve always the cause of P0402?
Not always — on Ford vehicles in particular, the DPFE sensor is statistically the most common cause. Replacing the EGR valve without first testing the DPFE sensor often results in the code returning, so test the sensor first.
Will cleaning the EGR valve fix P0402?
It can, especially if heavy carbon deposits are holding the valve open or blocking the passage. However, if the valve itself is mechanically faulty or the DPFE sensor is defective, cleaning alone will not resolve the fault.
Does P0402 affect my emissions test?
Yes. P0402 illuminates the MIL, which is an automatic failure in most OBD-II-based emissions inspections.
Disabling P0402 in software
RaceTune can permanently disable P0402 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P0402 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C74 verified 2 software versions
- Bosch EDC17C50 verified 1 software version
- Bosch EDC17CP09 verified 1 software version
- Bosch EDC17CP44 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0402 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file