Excessive EGR Flow Detected (P0402)
The P0402 code indicates that the Engine Control Module (ECM) has detected excessive exhaust gas recirculation (EGR) flow. This means more exhaust gas is being recirculated into the intake manifold than intended, which can disrupt the air-fuel mixture and cause performance issues. The EGR system reduces NOx emissions by recirculating a portion of exhaust gases back into the combustion chambers. Excessive flow can be caused by a stuck-open EGR valve, a faulty EGR pressure sensor, or blocked passages.
01. Most Common Causes
- Stuck open EGR valve
- Faulty EGR pressure sensor
- Blocked or restricted EGR passages
- Damaged EGR vacuum lines or solenoid
- Carbon buildup in the EGR system
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or stalling
- Engine hesitation or poor acceleration
- Increased fuel consumption
- Failed emissions test
03. Step-by-Step Diagnosis
Step 1: Scan the vehicle for codes and verify P0402 is present.
Step 2: Visually inspect the EGR valve, vacuum lines, and electrical connections for damage or carbon buildup.
Step 3: Test the EGR valve operation by applying vacuum or using a scan tool to command it open/closed.
Step 4: Check the EGR pressure sensor (DPFE) with a multimeter or scan tool for proper voltage readings.
Step 5: Inspect and clean EGR passages and the intake manifold for carbon deposits if necessary.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short trips, but prolonged driving may cause poor performance, increased emissions, and potential damage to other components. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts like a new EGR valve or sensor, plus labor if done by a shop. DIY cleaning can be cheaper.