P0400 - Exhaust Gas Recirculation Flow Malfunction

EGR flow is not behaving as the system expects.

Code Overview

EGR flow is not behaving as the system expects.

Common Causes

• Carbon-clogged EGR passages
• Faulty EGR valve
• Vacuum or control issue
• DPFE/feedback problem

Diagnostic Steps

1. Inspect EGR passages for carbon buildup
2. Command the EGR valve and watch response if possible
3. Check vacuum supply or control wiring

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

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Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.