P1765 – Transmission Control Relay (Toyota)

Description

The ECM detected a malfunction in the transmission control relay affecting power delivery to the TCM.

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Symptoms

Failsafe mode
Harsh shifting
Delayed shifting
No communication
Check engine light

Causes

Faulty relay
Corroded contacts
Wiring issues
Connector failure
Voltage instability

Diagnosis

Test relay operation
Inspect wiring
Check connectors
Measure voltage
Scan TCM data

Repair

Replace relay
Repair wiring
Clean connectors
Stabilize voltage