The misfire is very dangerous for your engine. A vehicle engine usually misfires due to insufficient combustion of the air/fuel mixture. The proper combustion of the air-fuel mixture is critical for the smooth running of the engine. When your engine cylinder 5 misfires, the powertrain control module (PCM) triggers the P0305 engine code. This article explains the P0305 code symptoms, its causes, and how to fix it.
P0305 Code Definition
The P0305 code stands for “Cylinder 5 Misfire Detected.”
What Does the Code P0305 Mean?
The P0305 code indicates that your powertrain control module (PCM) has detected a misfire on cylinder number 5.
The vehicles usually contain four, six, or eight cylinders. These cylinders are arranged in various arrangements.
To increase the engine power, you will need to increase the number of cylinders. Each cylinder contains a piston, fuel injector, spark plug, ignition coil, and fuel pressure sensor.
A misfire can occur when there is poor combustion of the fuel/air mixture within the cylinder. Having enough fuel burning is very important for the engine to work efficiently. Without it, fuel combustion will not occur, and the engine will not receive power.
When your powertrain control module (PCM) detects a misfire on engine cylinder number 5, it triggers the trouble code P0305.
Causes of P0305 Code
The P0305 engine is triggered due to one or more of the following causes:
- Damaged wiring of the cylinder number 5
- Bad spark plugs
- Faulty ignition coils
- Low fuel levels
- Dirty fuel
- Faulty engine valves
- Oil leakage in the combustion chamber
- Clogged or bad EGR valve
- Faulty or damaged fuel injector
- Bad fuel pump
- Damaged distributor cap
- Poor compression in cylinder 5
- Faulty O2 sensor
- Head gasket leaks
- Faulty MAF sensor
- Bad catalytic converter
- Faulty fuel pressure sensor
- Faulty oil distributor
- Faulty crankshaft sensor
- A faulty throttle position sensor
- Vacuum leaks
- Clogged throttle body
- Bad camshaft sensor
- Exhaust leaks
- Bad PCM
Symptoms of P0305 Code
- Engine stalling
- Fuel smell from the exhaust pipe
- The vehicle will not start or is difficult to start
- Poor fuel economy
- Rough idle
- Illuminated check engine light
- Limp mode
- Misfires
- A reduction in the engine power
- Poor car acceleration
- Jerking when driving
How to Diagnose the P0305 Trouble Code?
- Use an OBD-II scanner to find the trouble codes. Utilize the freeze frame data to check what’s going on. Continue the troubleshooting based on the other trouble codes you may find.
- Clear the codes. Test drive your car. If the codes return, then check other parts.
- Inspect the coil pack, wires, or spark plug on cylinder 5 to see if it is damaged or worn. Replace any of these parts if needed. You can try to move over the spark plug and ignition coil to another cylinder to see if you get a trouble code on the other cylinder instead – if so, replace the faulty spark plugs and ignition coil.
- Examine the ignition coil for cylinder number 5.
- Inspect the intake system for vacuum leaks.
- Check the fuel injectors. If any of your fuel injectors are damaged, replace them.
- If your car has a distributor cap and ignition cables, inspect them and replace them if needed.
- Perform a compression test of cylinder 5 to check its compression system.
- Properly inspect the camshaft timing.
- Check the shaft or timing belt if needed.
- If all the above parts are working efficiently, and you are still getting the P0305 code, your PCM may be bad.
Common P0305 Code Diagnostic Mistakes
- Not switching the coils and spark plug to a different cylinder and rescanning to check if the misfire moves to another cylinder to see if the coil or spark plug is bad.
- Replacing the unnecessary components
- Not switching one part at a time with various cylinders to detach the bad part.
- Not clearing the error codes after fixing the codes
- Not properly inspecting all the parts
- Not performing a test drive after clearing the codes
- Installing the new parts without testing them
Repair Cost of P0305 Code
The repair cost of the P0305 code varies according to your vehicle model, labor cost, and the repair of the relevant part. To fix the P0305, your vehicle may need one or more below given repairs:
| Parts | Cost |
| Leaking valve fix | $400 to $2,600 |
| Spark Plug replacement | $60 to $260 |
| Fuel pump replacement | $250 to $1,090 |
| Piston ring replacement | $900 to $5,100 |
| Fuel injector replacement | $1400 to $2000 |
| Spark plug wiring repair | $170 to $250 |
| Ignition Coils | $220 to $650 |
What repairs can fix the P0305 Code?
When your vehicle triggers the P0305 code, it is compulsory to fix it as soon as possible. It is not recommended to drive with this code for a long distance. Driving with this code for a long time may lead to costly repairs. To fix the P0305 engine code, you need one or more of the following repairs:
- Clearing the error code and performing a test drive
- Replacing the bad spark plug
- Replacing the bad fuel pump
- Replacing or repairing the damaged cylinder
- Replacing or fixing the head gasket leaks
- Replacing the damaged or corroded spark plug wires
- Replacing the bad or damaged fuel injectors
- Replacing or repairing the damaged coil pack wires
- Replacing the bad EGR valve
- Replacing the bad O2 sensor
- Replacing the burned valves
- Replacing the bad MAF sensor
- Repairing the fuel rail leaks
- Repairing the vacuum leaks
- Replacing the bad crankshaft sensor
- Replacing the bad camshaft sensor
- Replacing the damaged distributor cap
- Diagnosing and repairing any related trouble codes stored by the PCM
How Serious is the P0305 Code?
The trouble code P0305 is considered a serious trouble code. Driving with an engine misfire is very hazardous, especially if your vehicle starts to stall in the middle of the road. If your engine starts stalling, it might be hard to get it started back up, leaving you in a dangerous condition.
Therefore, you must fix the P0305 trouble code immediately. The engine misfire may also badly damage the parts of the engine, which may lead your vehicle to an expensive repair.
FAQ Section
What would cause a P0305 code?
Engine code P0305 could be caused by a number of things, including a bad spark plug, bad fuel injector, insufficient fuel, bad fuel pump, insufficient fuel pressure, vacuum leaks, bad engine valves, or bad PCM.
Can I drive with a cylinder 5 misfire?
No, you shouldn’t drive with an engine misfire. Driving with a misfire is very dangerous and can damage your engine. Therefore, it is recommended to promptly fix this code.
Can a bad spark plug cause the P0305 code?
Yes, a bad spark plug is one of the major causes of the P0305 code. A bad spark plug doesn’t generate sufficient spark to burn the air-fuel mixture efficiently. The poor combustion of the air-fuel mixture in engine cylinder number 5 causes misfiring and P0305 code.
Can a bad fuel injector cause P0305?
Yes, a bad fuel injector may lead to the P0305 engine code. A clogged or faulty fuel injector doesn’t deliver sufficient fuel to the engine cylinder and causes a poor air-fuel mixture. When this poorly mixed air and fuel mixture burns, it causes misfiring.
Can P0305 code fix itself?
No, the P0305 code can’t be fixed itself until you won’t fix the main issue.
