What this code means
P0685 may mean the PCM power control circuit is not behaving as expected, or the PCM may be detecting an internal power-control related problem.
What the vehicle may do
- The vehicle may have intermittent power-up or starting symptoms.
- The code may return after a key cycle and short idle period.
- The vehicle can sometimes appear to run normally when the fault is intermittent.
Possible fault areas
- Possible PCM power feed, relay, or fuse concerns.
- Possible loose terminals, poor connector fit, or wiring connection issues between the PCM and fuse or relay area.
- Possible PCM ground or battery cable connection concerns.
- Possible PCM software or PCM-related concern.
Diagnostic path
Opening context
On this 2010 to 2016 Honda CR-V with the 2.4 gas engine, P0685 points to a PCM power control circuit or internal circuit malfunction. In plain language, the PCM may not be seeing the power control path behave the way it expects, or it may be detecting an internal power-control concern. The vehicle may have intermittent power-up issues, may set the code after a key cycle, or may seem normal until the fault is duplicated. The broad areas to keep in mind are the PCM power feed path, the main relay and fuse, connector and terminal fit, PCM grounds, battery connections, PCM software, and the PCM itself. Before getting deep into this one, start with the basic system checks and follow a structured diagnostic approach.
Duplicate the fault first
Start by verifying the problem exactly. Turn the vehicle to the ON mode. Clear the DTC with the HDS, then start the engine and let it idle for 30 seconds. After that, turn the vehicle to the OFF, LOCK mode, then turn it back to the ON mode. Now check for pending or confirmed DTCs with the HDS and see whether P0685 is indicated again.
If P0685 returns
If P0685 is indicated after that sequence, the failure has been duplicated. At that point, update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the code goes away after the PCM update, troubleshooting is complete. If the code goes away with a known-good PCM installed, replace the original PCM.
If P0685 does not return
If P0685 is not indicated, treat it as an intermittent failure. Before condemning the PCM, check for loose terminals at the IGP, ECU, and FI main relay output line connectors. If captured operating data is available for this code, try to reproduce the failure under those same captured conditions. Then inspect the likely power and ground side issues: the PGM-FI main relay, the PGM-FI main fuse, poor or loose connections between the PCM and the under-hood fuse and relay box, poor or loose PCM ground terminals and connections, poor or loose 12 volt battery cables and connections, and the 12 volt battery.
Repair verification and takeaway
Keep the verification separate from the inspection work. For the recheck, use the same ON mode, clear-code, idle, OFF LOCK, and ON mode sequence, then check with the HDS and confirm P0685 stays gone. The takeaway is simple: prove whether the fault is repeatable first. If it repeats, follow the PCM software or known-good PCM path. If it does not repeat, slow down and chase the intermittent power, ground, fuse, relay, terminal, and battery connection issues before replacing anything. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0685 is best handled by first proving whether the fault repeats, then separating a repeatable PCM software or PCM path from an intermittent power, ground, relay, fuse, terminal, or battery connection
For more guided automotive diagnostics, visit STEP Diagnostics.
