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Error Code P0313 is defined as Misfire Detected with Low Fuel. It refers to an engine misfire under low fuel conditions.
This code is a generic trouble code, which means it applies to all vehicles equipped with OBD-II, especially all makes and/or models of vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs of course, vary from one make/model to another.
Error Code P0313 indicates that the PCM (powertrain control module, also known as ECM or engine control module in others vehicle makes) has detected a misfire problem accompanied by low fuel condition.
The PCM uses crankshaft position, camshaft position, as well as engine RPM to calculate the amount of fuel to deliver and the ignition timing. Variations in both crankshaft and camshaft positions, as well as RPM, help the PCM detect an engine misfire. If the detected engine misfire is severe enough to cause serious damage to the catalytic converter(s), a code will pop up in the PCM and trigger the Check Engine light. If the engine misfire is not considered serious, and there is no catalytic converter damage, the Check Engine light may still flash for a period of time (usually under acceleration) then go off.
The Error Code P0313 is set when the PCM, through the different signals from a range of sensors, discovers there is a misfire due to lean (not enough fuel, too much air) condition. This is because a lean condition occurs when there is not enough fuel to cover the fuel pump, sporadic pressure surges because of the pump’s failure to pick up the remaining fuel.
This is easily one of the most ambiguous codes out there. However, if taken on a face value, diagnosed properly and corrected, is actually easy and straightforward to fix.
Symptoms of Error Code P0313 include:
- Rough running engine
- Hard starting or no start at all
- Lack of power
- Hesitation on acceleration
The most common cause of this error code is lean fuel mixture, which is usually caused by bad fuel pump, clogged fuel filter, clogged fuel injector, shorted or open circuits in the fuel pump or fuel injection system, corroded or unplugged electrical connectors. Other possible causes include:
- Low fuel level exposing fuel pump
- Failed fuel pressure regulator
- Poor electrical connectors
- Other possible causes may be problems in:
- Faulty ignition wires
- Faulty spark plugs
- Faulty carbon-fueled valves
- Faulty reluctor wiring
- MAF (mass airflow sensor)
- Faulty coil packs
- Faulty distributor cap
- Vacuum leak
- Lack of compression
How to Check
Experts suggest that it is important to check for related codes of this error code at TSBs (technical service bulletins) online. If the fuel system is not what is causing the problem, several makes of vehicles have unusual problems that tend to set this code in the system. More so, it is also important to check your factory and extended warranty to see if your vehicle is covered for this code, and for how long.
As with other trouble codes, checking this code requires a code scanner. Because this code has a lot of related codes, there may be other codes present to direct to a particular area, such as: P004, P0091, P0103, P0267, and P0304.
If any of these codes are present, they should be repaired first and the vehicle should be retested to make sure they are cleared from the scanner.
How to Fix
To fix this error code, you can follow these steps:
Look for the fuel test port on the fuel rail and then connect the fuel pressure tester. Allow the fuel pressure to drain in to a gas can by opening the valve on the tester. Then close the valve.
Raise the vehicle and then replace the fuel filter.
Next, turn the key on and then check for leaks.
Then, loosen the fuel pump module by pulling the connector, and then check the voltage for fuel pump. You will need a helper on this step, as someone will have to cycle the key on for 5 seconds and off for another 5 seconds. The PCM will energize the pump for two seconds. If the PCM doesn’t see the engine turning it will turn off the fuel pump.
Check the terminals for power while simultaneously listening to the pump energize. If there is an unusual sound or there is no sound, that means the pump is failing. Also, make sure both the connector and the wiring harness are in good shape.
Then, lower the vehicle and start the engine. Take note of the fuel pressure at idle. If the engine seems to run better, and the fuel pressure stayed within limits (as per the service manual), then the problem is repaired.
If the problem still isn’t solved, then you should check if there are vacuum leaks to the intake manifold.
Pull the vacuum hose off of the fuel pressure regulator then check for fuel inside the hose. Fuel in the hose means the diaphragm has failed.
For faulty fuel pumps, you need to take your vehicle to a certified service facility for a thorough repair. Dropping the fuel tank can be extremely dangerous, as one spark is all it takes to cause a serious disaster. Thus, never attempt to conduct the repair alone or you will risk a serious accident.