The P1313 through P1318 codes indicate that your car's engine is experiencing misfires in all six cylinders
. The "emission relevant" description means the misfires are severe enough to cause a significant increase in pollutants and could potentially damage your catalytic converter. When multiple cylinders misfire, the cause is typically not an individual component, like a single bad spark plug or coil. The issue is more likely related to a system or component that is common to all cylinders.
Common causes for multiple misfires
- Fuel delivery problems: A weak fuel pump, a clogged fuel filter, or faulty fuel pressure regulator can cause low fuel pressure, starving all the cylinders of the necessary fuel for combustion.
- Major vacuum leak: A large vacuum leak in the intake manifold gasket, a damaged vacuum hose, or another vacuum-controlled component can allow unmetered air into the engine. This upsets the air-fuel ratio, causing widespread misfires.
- Contaminated fuel: If you recently refueled, it's possible that contaminated or bad fuel is causing the misfires.
- Ignition system failure: A fault in a main ignition component, such as the Crankshaft Position Sensor (CKP) or Camshaft Position Sensor (CMP), can cause the engine's timing to be incorrect, leading to misfires across all cylinders.
- Wiring harness issues: Damaged, loose, or corroded wiring that affects the ignition or fuel injector circuits for multiple cylinders can trigger these codes.
- Mass Airflow (MAF) sensor fault: A faulty MAF sensor can send incorrect air-volume data to the engine's computer, causing it to miscalculate the proper air-fuel mixture.
- Engine control module (ECM/PCM) issue: While less common, a faulty engine computer that sends incorrect signals to the coils or fuel injectors can cause misfires across the entire engine.
How to diagnose the problem
Diagnosing multiple misfires requires a systematic approach, beginning with the simplest and most common issues.
- Check for obvious issues: First, check if the engine has low or contaminated oil, as this can indicate a serious internal mechanical problem. Visually inspect the engine compartment for any disconnected or cracked vacuum hoses.
- Inspect ignition components:
- Spark plugs: Examine the spark plugs. Worn, fouled, or incorrectly gapped plugs can lead to misfires.
- Ignition coils: If your engine uses a coil-on-plug system, check for cracks or signs of arcing on the coil bodies. To see if a specific coil is bad, you can swap it to a different cylinder and see if the misfire code follows.
- Test fuel system pressure: Use a fuel pressure gauge to test for proper fuel delivery. A low reading can confirm a problem with the fuel pump, filter, or regulator.
- Scan for other codes: Use an OBD-II scanner to check for additional codes. A P0300 (random multiple misfire) code often accompanies specific cylinder misfire codes and confirms a broader problem.
- Look at live data: Monitor engine sensor data with a scan tool. Pay attention to readings from the O2 sensors, MAF sensor, and fuel trims. Incorrect readings can help pinpoint the system with the issue.
- Perform a compression test: If all other possibilities are exhausted, a compression test can check for serious internal engine damage, such as a faulty head gasket, bent valve, or broken piston rings.
What to do next
Because you have multiple misfire codes, you should stop driving the vehicle to prevent potential damage to the catalytic converter. If you are not experienced with engine repair, it's best to take the car to a qualified mechanic for a proper diagnosis.
