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P0301

The codes all reference engine misfires. Continued misfires can cause the catalyst to fail and block the exhaust. The past diagnosis you had that the coils could be bad was correct. The coils (https://www.yourmechanic.com/services/ignition-coil-replacement) and plugs should be replaced (https://www.yourmechanic.com/services/spark-plugs-replacement)...

The codes P0300 (https://www.yourmechanic.com/article/p0300-obd-ii-trouble-code-random-multiple-cylinder-misfire-detected-by-jamahl-walker) and P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker) are coming up for a misfire on cylinder number 1. Check the cylinder for spark, fuel, and air. Check the spark plug (https://www.yourmechanic.com/services/spark-plugs-replacement) and make sure that it is firing. The spark plug...

Hello and thanks for your question. There is a misfire detected between cylinder 1 and cylinder 2. The codes P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker) and P0302 (https://www.yourmechanic.com/article/p0302-obd-ii-trouble-code-cylinder-2-misfire-detected-by-jamahl-walker) are directly related to cylinder 1 and cylinder 2. The code P0300 (https://www.yourmechanic.com/article/p0300-obd-ii-trouble-code-random-multiple-cylinder-misfire-detected-by-jamahl-walker) means that there...

Diagnostic Trouble Code P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker) means that Cylinder No. 1 is misfiring but the causes of that can be very varied. The fuel injector could simply be dead or there is little cylinder compression due to a burned valve or...

Fault codes for P0300 (https://www.yourmechanic.com/article/p0300-obd-ii-trouble-code-random-multiple-cylinder-misfire-detected-by-jamahl-walker), P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker), P0302 (https://www.yourmechanic.com/article/p0302-obd-ii-trouble-code-cylinder-2-misfire-detected-by-jamahl-walker), etc. indicate misfires. P0301 would indicate cylinder #1 misfiring, P0302 would indicate cylinder #2 misfiring,etc. Code P2159 has to do with the VTEC system malfunction. If all this started after the...

All the generated codes will need further inspection from a mechanic. The P0300, P0301, and P0305 are all misfires in the engine and could also cause some of the additional codes. You will need to have a diagnostics done and...

Hey there. In order to check the cylinder for spark you have to remove the coil and insert a spark tester into the coil after reconnecting it. Then you can check to see if it has spark. The injector will...

Hello there. Misfires are a common problem with your 1997 Subaru Impreza as the vehicles ages. The most common failures are the spark plugs (https://www.yourmechanic.com/services/spark-plugs-replacement), coil (https://www.yourmechanic.com/services/ignition-coil-replacement), plug wires (https://www.yourmechanic.com/services/ignition-cable-spark-plug-wires-replacement), fuel injectors (https://www.yourmechanic.com/services/fuel-injector-replacement), fuel pump (https://www.yourmechanic.com/services/fuel-pump-replacement), vacuum leaks (https://www.yourmechanic.com/article/is-it-safe-to-drive-with-a-vacuum-leak), or...

Hello. When you have this many codes (https://www.yourmechanic.com/article/how-to-read-and-understand-check-engine-light-codes-by-jason-unrau) you either have an issue with the voltage system in the vehicle being low due to a bad connection, a battery that is failing (https://www.yourmechanic.com/services/battery-replacement), or a faulty alternator (https://www.yourmechanic.com/services/alternator-replacement). It can...

Hey there. Your logic is absolutely correct. This is in fact one of the most commonly used ways to diagnose a bad ignition coil. If the trouble code turns to a P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker), the ignition coil is faulty (https://www.yourmechanic.com/services/ignition-coil-replacement). If...

Hello, thank you for writing in. The vehicle's cooling leak may be causing the misfire. The leak needs to be repaired first, and then we can take any other issues from there. The starting problem may also be the vehicle's...

Oxygen sensor function can be tested and verified using an oscilloscope, automotive scope, or a vehicle specific, manufacturer scan tool. A faulty O2 sensor, if it exists can be found. However, the Diagnostic Trouble Code you are referring to, namely...

Hi there. The transmission may have a failed harness or a failed computer (TCM). With having all of the shift solenoids and the torque converter clutch not functioning correctly, then there is a connection error. Remove the harness to the...

Hi there. Check the spark plugs and fuel injectors for cylinder 1 and cylinder 3. Both cylinders are misfiring. If the plugs are good and the fuel injectors are firing, then there could be a problem with the internals of...

Hi there. From the description you have provided, for the P0301 rough idle and heavy misfire and P0456 evaporative small leak detected, the problems are unrelated. The P0301 is a #1 cylinder misfire code. It could be, a spark plug...

Hi there. If this vehicle is having an idle concern, I have to ask if you may be having a stumble or stall issue when coming to a stop. If so, your vehicle may be covered under a special service...

Hello there, the P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker) Cylinder 1 misfire is a common code on your 2002 Chevrolet Trailblazer. When a misfire code is seen it is telling us that the cylinder is not firing as it is supposed too. This means...

Hi there. Your vehicle has a sequential fuel injection system. When the computer detects a fault, it converts to port fuel injection (bank to bank/limp mode). The most likely cause could be an electrical short in the odd bank of...

P0301 (https://www.yourmechanic.com/article/p0301-obd-ii-trouble-code-cylinder-1-misfire-detected-by-jamahl-walker) is a misfire in number one cylinder. I believe you are already aware of this. A common problem on these is the injector assembly. I would do everything below before I condemn it. If I were there in...

All these codes point to engine misfires. You should pull the spark plug wires (https://www.yourmechanic.com/services/ignition-cable-spark-plug-wires-replacement) to see if oil is on the spark plug wires causing the misfire. You would need to replace the valve cover gaskets (https://www.yourmechanic.com/services/valve-cover-gasket-replacement) and spark...