Skip the auto shop - Our mechanics make house calls

Q: car cranks but wont start. check engine light on. code p0685

asked by on

Drove home from work, stopped on my way. car would crank but not start. my dash said "engine power reduced" i unhooked the battery and came back to the car an hour or so later and it started right up, I drove it about 3 miles and same thing, except this time it happened while i was driving. I called a tow truck driver and when he got there he jump started the car and it started right up on the first try. "Engine power reduced" warning went away but check engine light came on. I bought a code reader and it gave me p0685 "Ecn/pcm power control module relay/open". Car starts anytime i try to start it now, but i dont want to drive it anywhere and have to get it towed home again.

My car has 149000 miles.
My car has an automatic transmission.

A: The code P0685 indicates a problem with Eng...

The code P0685 indicates a problem with Engine Control Ignition Relay Control Circuit. This may have a poor connection or need to be replaced. I would recommend having an expert from YourMechanic come to your home to diagnose and repair.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Cigarette lighter not working.

It is very likely that the fuse for the cigarette lighter circuit has failed. This is not uncommon. There is also the possibility that the actual cigarette lighter receptacle has failed as well. I would ask for help from one...

Q: My car is still dying out after replacing the alternator and battery

Remove the negative battery cable from the battery. Get a digital meter and check the voltage from the battery terminal and the battery cable without having the cable touching the terminal. If there is something on in the vehicle with...

Q: How Do Spark Plugs Work in an Engine?

Spark plugs are used to ignite the air/fuel mixture in the combustion chambers of every internal combustion engine. To accomplish this, spark plugs have two electrodes between which a high voltage spark will jump. One electrode is located in the...

Related articles

How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...