What does it mean?
This is a generic powertrain code, meaning it covers all makes/models from 1996 onward. However, specific troubleshooting steps vary by vehicle.
The P0313 code refers to an engine misfire detected under low fuel conditions. It is one of the few ambiguous vehicle codes that, taken at face value, diagnosed and fixed seems fairly straightforward.
The code is set when the computer—through signals from a range of sensors—determines that the engine failure is due to a lean condition (too much air and not enough fuel). If the fuel level is low enough to uncover the fuel pump, sporadic pressure increases due to the pump’s inability to pick up the remaining fuel will cause a “lean” condition.
In all likelihood, you have either let the fuel level drop to a low level before refilling, or you have a legitimate fuel delivery issue. If the fuel system proves to be functioning correctly, several other mechanical failures can cause this scenario.
Symptoms
Symptoms may include:
P0313 misfire detected with low fuel fault code
Rough running engine
Hard or no start
Hesitation on acceleration
Lack of power
Potential Causes
Causes of this DTC may include:
Likely:
Low fuel level exposing the fuel pump
Failing fuel pump
Clogged fuel filter
Failed fuel pressure regulator
Clogged or failed fuel injectors
Short or open circuit in the fuel pump harness
Poor electrical connectors
Additional Possibilities:
Spark plugs
Ignition wires
Faulty reluctor ring
Carbon-fouled valves
Mass airflow sensor
Faulty distributor cap
Faulty coil packs
Lack of compression
Large vacuum leak
Diagnosis and Repair
It is important to start by going online and checking all TSBs (Technical Service Bulletins) related to this code. If the fuel system is not the issue, several vehicles have a particular problem that tends to set this code.
For example, BMWs have a set of three oil separator hoses under the intake manifold that, when cracked, create a vacuum leak that sets this code.
Check your factory and extended warranty to see if it is still covered and for how long.
Purchase a code scanner from your local auto parts store or borrow one. They are relatively inexpensive and not only retrieve codes but have a cross-reference sheet for explanations and can reset the computer once finished.
Connect the scanner to the OBD port under the dashboard on the driver’s side. Turn the key to “On” and press the “Read” button. Note all codes and cross-reference them with the code sheet. Additional codes might be present that will direct you to a particular area, such as:
P0004 Fuel Volume Regulator Control Circuit High
P0091 Fuel Pressure Regulator 1 Control Circuit Low
P0103 Mass or Volume Air Flow Circuit High Input
P0267 Cylinder 3 Injector Circuit Low
P0304 Cylinder 4 Misfire Detected
Repair any additional code and retest by clearing the code with the scanner and test driving the vehicle.
If no codes are present, start with the fuel filter. The following diagnostic and repair procedures require some special tools:
Special wrenches to remove the fuel filter
Fuel pressure tester and adapters
Gas can
Volt/Ohm meter
Ensure there is at least half a tank of fuel.
Connect the fuel pressure tester to the fuel test port on the fuel rail.
Open the tester valve and let the fuel pressure flow into a gas can. Close the tester valve.
Lift the vehicle and replace the fuel filter.
Turn the key and check for leaks.
Remove the fuel pump module connector and check voltage at the fuel pump. To do this, an assistant will need to press the key for five seconds and turn it off for five. The computer powers the pump for two seconds. If the computer does not see the engine turning, it shuts off the fuel pump.
Probe the connector terminals for power. At the same time, listen for the pump to power up. If there is no sound or an unusual sound, the pump is failing. Ensure the wiring harness and connector are in good condition.
Lower the vehicle and start the engine. Note the fuel pressure at idle. If the engine runs better and the fuel pressure is within specifications according to the service manual, the problem is solved.
If this does not resolve the issue, check for possible vacuum leaks in the intake manifold.
Remove the vacuum hose from the fuel pressure regulator. Look for fuel inside the hose. Fuel means the diaphragm has failed.
If the fuel pump is faulty, take it to a service center for replacement. This makes technicians nervous when dropping the fuel tank. A spark could cause a disaster. Do not attempt at home, for fear of blowing up your house and surrounding homes if an unfortunate accident were to occur.