P1600 – ECM Backup Circuit (Toyota)

Description

The ECM detected a malfunction in the backup power circuit, which maintains memory and operational readiness.

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Symptoms

  • Check engine light on
  • Intermittent no-start
  • Loss of learned values
  • Unstable idle
  • ECM resets unexpectedly

Causes

  • Weak battery
  • Corroded battery terminals
  • Faulty ECM backup circuit
  • Damaged wiring
  • Poor ground connection

Diagnosis

  • Check battery voltage
  • Inspect terminals
  • Test ECM power supply
  • Check ground points
  • Scan for related codes

Repair

  • Clean terminals
  • Repair wiring
  • Replace battery
  • Repair ground points
  • Replace ECM if necessary

Related Problems

Related Fault Codes