P0685 on Mitsubishi: How to Diagnose & Fix
ECM/PCM Power Relay Control Circuit/Open
1 Mitsubishi model · 1 documented issue · 1 critical
P0685 on Mitsubishi by model: symptoms, diagnosis and fix
A relay supplier used an improper maintenance procedure on its welding machine, so internal welds inside several relays used in the Outlander's engine-bay relay box were made incorrectly and can lose proper electrical conduction. Depending on which relay is affected, the result differs: failure of the engine control unit relay kills the engine while driving and the vehicle cannot be restarted; failure of the relay feeding the MIVEC variable valve lift assembly triggers a check engine light and reduced power; failure of the radiator fan relay stops the cooling fan and lets the engine overheat. Because it is a manufacturing defect in a specific production batch rather than a wear item, failures show up suddenly and at low mileage.
Common Symptoms
- Engine stalls while driving and will not restart
- Check engine light with reduced engine power
- Engine overheats because the radiator fan never comes on
- Coolant temperature warning lamp illuminates
How to Fix
Covered by NHTSA safety recall 17V609000 (Mitsubishi campaign SR-17-005) — the dealer replaces the affected relays free of charge regardless of mileage or ownership history. Check the VIN on nhtsa.gov/recalls; if the campaign was never performed, book it before chasing the symptom. Outside the recall population, a stall-and-no-restart on these cars is worth testing at the relay box first (swap in a known-good identical relay) before condemning the ECU, crank sensor or fuel pump — relays are a fraction of the cost of the parts they mimic.
Sources for this issue (4)
P0685 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0685 mean on a Mitsubishi?
P0685 stands for "ECM/PCM Power Relay Control Circuit/Open." An open or general fault in the control circuit for the ECM/PCM main power relay. The module cannot properly control the relay that supplies its own switched power. On Mitsubishi it is documented across 1 model: Outlander.
What are the most common causes of P0685?
The most common causes of P0685 are: Faulty ECM/PCM power relay, Open in the relay control circuit, Corroded/damaged connectors, Blown fuse, Internal PCM driver fault. The specific cause varies by vehicle.
How much does it cost to fix P0685 on a Mitsubishi?
Repair costs vary widely with the root cause and Mitsubishi model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.