Error code

OBD2 P0400

OBD2P0400
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Exhaust Gas Recirculation Flow.

Severity

moderateCan drive, but performance issues may occur.

Summary

P0400 indicates a malfunction in the Exhaust Gas Recirculation (EGR) system, which is responsible for reducing harmful emissions by recirculating exhaust gases back into the engine.

Symptoms

  • Hard or no starting conditions
  • Rough idling due to unstable combustion
  • Reduced acceleration at high loads
  • Decreased fuel economy

Common Causes

  • Clogged EGR valve passages
  • Defective MAP sensor
  • Faulty EGR vacuum control solenoid or electric control solenoid
  • Vacuum leaks in the system
  • Exhaust leaks
  • Poor crankcase ventilation due to clogged PCV valves

Diagnosis

  1. Inspect vacuum lines and wiring for damage or leaks.
  2. Test EGR valve with a hand-held vacuum pump to check its functionality.
  3. Check the MAP sensor and related solenoids for faults.
  4. Clear codes after repairs and retest system.

Fixes

  • Replace faulty components such as the EGR valve, vacuum control solenoid, or MAP sensor.

FAQ

What does P0400 mean?

P0400 indicates a malfunction in the Exhaust Gas Recirculation (EGR) system.

How do I fix P0400?

Fixes include inspecting and replacing faulty components like the EGR valve, vacuum control solenoid, or MAP sensor.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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