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P0685 — ECM/PCM Power Relay Control Circuit/Open

The PCM power relay (main relay) circuit has an open — PCM may lose power.

Severity: CriticalRepair: $30-$500Difficulty: Medium

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Common symptoms of P0685

Common causes of P0685

Repair cost & difficulty

Typical cost to fix P0685: $30-$500 · Difficulty: Medium

Pro tip: The main relay is the power supply for the entire engine management system. Check relay and its fuse first.

Vehicles commonly affected

All makes

Related trouble codes

P0686

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ScanFixAI is a diagnostic aid, not a substitute for professional repair. Cost estimates are typical ranges and vary by vehicle and region.