P0402

What P0402 means

P0402 means too much EGR flow is reaching the intake — usually because the EGR valve is stuck open or leaking, or carbon is holding it off its seat. Excess EGR at idle dilutes the mixture and makes the engine run rough or stall.

Symptoms

• Check engine light on
• Rough idle or stalling, especially at stops or when decelerating
• Hesitation and light pinging under load
• Hard starting when warm

Likely causes (most common first)

1. EGR valve stuck open or not seating (carbon buildup)
2. Faulty EGR valve position sensor
3. Faulty DPFE / exhaust-pressure sensor (common on Ford)
4. Vacuum control or solenoid fault holding the valve open
5. Clogged EGR passages leaking past the valve

Can I keep driving?

Yes, but expect rough idle. Cleaning the EGR valve and passages often clears it; sustained stalling in traffic is the main risk.

Typical repair cost

DIY fixes can start near $50 (parts only). Shop repairs for P0402 typically run up to $500 depending on the underlying cause and vehicle. Start with the most common cause — EGR valve stuck open or not seating (carbon buildup) — before throwing parts at it.

Recommended parts & tools for P0402

Our buyer’s guides cover the tools and parts that pair with AXLY:

As an Amazon Associate, AXLY earns from qualifying purchases.

Related codes

Confirm P0402 yourself in 60 seconds

Two cheap things and you can read P0402 yourself — plus every other stored code and live engine data, free. No subscription.