P1768 – Transmission Control Relay Electrical (Toyota)

Description

The ECM detected an electrical malfunction in the transmission control relay circuit.

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Symptoms

  • Failsafe mode
  • Harsh shifting
  • Delayed shifting
  • No communication
  • Check engine light

Causes

  • Open or shorted wiring
  • Faulty relay
  • Connector corrosion
  • Voltage instability

Diagnosis

  • Test relay resistance
  • Inspect wiring
  • Check connectors
  • Measure voltage

Repair

  • Replace relay
  • Repair wiring
  • Clean connectors
  • Stabilize voltage