Power lose


Asked by Aug 03, 2015 at 06:28 PM about the 2003 Honda Accord LX

Question type: Maintenance & Repair

2003 LX Driving at high way speed tach and speedo drop to zero charge light comes on
trip indicator flashes .Retrieved code P0 685. Has anyone seen this. Could a dieing
battery cause this .Alternator out put 14 volts.

10 Answers


Also when the above take place engine is not affected at first only after the check engine light comes on.

Kelly Mayo

P0685 ECM/PCM Power Relay Control Circuit Malfunction - ECM power control circuit is open or shorted - Failed ECM power relay - Failed ECM If its not the ecu, as it's been replaced, it's likely the relay where the issue lies. also, check your battery terminals and connections. a lose feed line could cause power issues.


Is the relay replaceable if so where is it.

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If the ECM/PCM malfunctions or becomes shorted. That would be constant and not intermittent problem. After clearing the code it didn't reappear after starting the engine.

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Kelly Mayo

trebor66 ...and what..is the problem fixed..still have code???


Kelly here is what I have done. After having the problem this morning. I charged battery installed back in car started it up checked voltage at terminals (14 volts at idle).My drive to and from work 20 miles +/- at about 5 miles to battery light comes on again and the tack and speedo drop to 0 for a moment no affecting engine speed doing 70 on free way.After a few get off freeway and now the check engine light is on and off with a little hesitation. Made it home access the code as stated earlier cleared it and checked the connections behind the radio(it had issues of not turning on no volume).Checked the system voltage with scan tool it showed about 8 volts +/- .Charged battery checked the battery connection found negative side clamp tight but could still turn it scraped clean and made it tight so it could not turn. Started right up turned on the A/C and headlights shut it off restarted no problem and no code .Your thoughts.

Kelly Mayo

at this point drive it again... short maybe when driving have to see..ill think on it.. i get so many questions...

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Best Answer

Honda's can be very temperamental when it comes to voltage. Having had similar problems but different codes over the years, my advice would be to change the battery, and then if still problems, the alternator . I have seen many alternators test out as good when in fact they are not.

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Update Kelly and JP1956. Drove it this morning did fine till about a mile to same issue, but no code.Read JP's comment about battery. Replaced battery drove home with A/C going ......NO ISSUES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I hope that fixed it thanks for all your help. Bottom line is a battery that is dieing could cause a lot of issues.The battery I replaced wasc 3 years old.


LOL hope you got a better grade of battery!

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