Error code P0302 is described as Misfire Detection Monitor – Cylinder 2 Misfire. This means the misfire detection monitor has detected an engine misfire, particular in the cylinder 2 of the engine.

Definition

Error code P0302 is a common error code that signifies a misfire issue on the engine’s cylinder, specifically cylinder #2. Modern vehicles are equipped with a computer with a misfire detection monitor that tells the scanning tool about misfire and detect which cylinder is having trouble. An engine misfire simply means lack of combustion, which can be a result from a lot of things, such as lack of spark, low compression, poor fuel quality, metering, or unmetered air entering the engine.

When a misfire on the engine happens, the vehicle will automatically trigger the Check Engine light and show a specific number. The last digit in the number signifies the number of the cylinder at fault. For instance, cylinder #1 will trigger the Error Code P0301; cylinder #2 will trigger the Error Code P0302, and so on.

Common Symptoms

  • Check Engine light is on
  • The engine is harder to start and may stumble or hesitate upon acceleration
  • In many cases, the vehicle will show performance problems such as rough idling, dying at stop signs, hesitation, lack of power on acceleration, and bad fuel consumption

Possible Causes

  • EVAP (Evaporative Emission System) concerns such as fuel vapor leak, which leads to the engine
  • Wrong fuel pressure
  • Poor fuel quality
  • Running out of gas
  • Wrong ignition timing
  • Faulty Mass Air Flow Sensor
  • Faulty Throttle Position Sensor
  • EGR (Exhaust Gas Recirculation) system concerns such as restricted ports or leak EGR valve
  • Base engine problems such as valve train issues, timing problems, low compression
  • Problems on the ignition system such as defective spark plugs or related wiring, problems on the ignition module or its wiring, problems on the ignition related sensor and its wiring

How to Check

When checking your vehicle for error code P0302, it is important to note the freeze frame info and duplicate the conditions that set the code through a test drive. This means you need to take note of the throttle position, engine load, RPM and road speed. This error code refers specific misfire, which may be difficult to detect.

For a cylinder misfire encounter, you need to switch components, such as spark plugs, coils, etc. so you can isolate the root cause of the misfire. Also, it is important to record other codes, as the misfire may be caused by a faulty component or system.

Here are the four common types of misfire and how to check for the code P0302.

Ignition Misfire

Check for any signs of wear and heat damage in all of the components of Ignition System. The Spark Plug terminals must not be blackened with soot, white caused by overheating combustion chamber, greenish if it’s caused by the coolant. Rather it should maintain a sandy color.

Ignition cables and its coils should be free of arcing. Scope check the Ignition System if possible to make sure the firing voltages are evenly firing, there should be about 8V to 10V per cylinder.

Take off the distributor cap and rotor (if there’s any) on the engine. Check the terminals and all contact points for signs of wear and tear, arching and corrosion build up.

Also, though OBD II vehicles comes with computer controlled trimming, make sure to verify that it’s the right spec, even if it’s using individual coils.

Lean Misfire

Pay attention to the Long Fuel Trim values as they specify how the Powertrain Computer is compensating to balance air/fuel ratio. If it is more than 10% in one cylinder bank and not the other, that can be a sign of vacuum leak, cracked or defect on the intake manifold on the particular bank. You need to determine what causes the computer to do this amount of compensation by checking the Fuel Trim “numbers” from the full range of operating conditions. An engine that is in good shape has 1% to 3% Long Term Fuel Trim numbers, either positive or negative.

Mechanical Misfire

There are two ways to check for mechanical misfire; Engine Idle Manifold Vacuum Test and Compression Test. Consistent compression readings (around 10% of each other), and at least 120 PSI per cylinder, minimum of 17-inchs of steady vacuum are all required for a smooth and complete combustion.

Powertrain Misfire

Out-of-round and badly warped rear brakes can cause a vehicle misfire, which shows symptoms such as violent jerking of the powertrain, and vehicle slowing from highway speeds. To check for this misfire, make sure your car get a thorough inspection to spot the misfire. The whole engine must be replaced to fix a wrongly perceived mechanical misfire that originates from the transfer case, driveshaft, transmission or front/rear differential

How to Fix

For vehicles that don’t show many symptoms, the simplest way to get rid of this error code is to reset the code and check it again.

If symptoms such as engine hesitating or stumbling, you need to check the wiring connectors that leads to the cylinder, such as the spark plugs.

Ignition components must be replaced as part of the regular maintenance schedule. Distributor cap, spark plugs and wires, and rotor (if applicable) must be replaced. Otherwise, inspect the coil (coil packs).

If you notice a smell of rotten eggs in the exhaust, that’s a sign of damaged catalytic converter, and it means the CAT converter must be replaced.

In some cases, the error code may be caused by defective fuel injectors.

For more tips and instructions to get rid of the Check Engine light and solve this error code, and for more information about different error codes, feel free to Contact Us.