P1616 – Immobilizer ECM Error (Toyota)

Description

The ECM detected an internal immobilizer-related malfunction affecting engine authorization.

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Symptoms

No start condition
Security light on
Intermittent start
Key not recognized
Failsafe mode

Causes

Internal ECM fault
Memory corruption
Voltage instability
Connector corrosion
Wiring issues

Diagnosis

Scan ECM
Inspect connectors
Check voltage stability
Test immobilizer communication
Verify grounds

Repair

Repair wiring
Clean connectors
Stabilize voltage
Replace ECM if necessary