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P0418 Powertrain

Secondary Air Injection System Relay "A" Circuit Malfunction

General electrical fault in the secondary air injection pump relay A circuit. Without the relay, the air pump cannot be commanded and the system cannot complete its cold-start function.

Affected components

  • Secondary air relay
  • Secondary air pump
  • Relay wiring

Common causes

  • High likelihood: Air pump relay failed
  • Medium likelihood: Wiring or connector fault

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions
  • A drive cycle may be required after repair

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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