OBD code information sheet
https://obdauto.ro/en/p0300
Random/multiple cylinder misfire
Selected definitionGeneral catalogue definition1 definitions availableChange
Choose the make reported by the scan tool or vehicle documentation. The same code can have different manufacturer meanings.
Technical explanation
The ECU detects random or multiple-cylinder misfires. Stop safely if the check-engine light flashes or the engine shakes severely.
Read the full technical explanation
P0300 identifies random or multiple-cylinder misfire without isolating one cylinder through this code alone. Monitoring may use crankshaft-speed variations to detect irregular combustion. Ignition, fuel delivery, air supply and engine mechanics can all be involved. Spark-plug and coil checks apply to spark-ignition engines, not automatically to diesels; examine the whole fault pattern before ordering parts.
Symptoms
Engine shaking or uneven idle.
Hesitation, weak acceleration or loss of power.
Steady or flashing engine light; the problem may occur only cold or under load.
Top suspects — what to check first
Suggested checking order, not statistical failure rates or a confirmed diagnosis. Priority can change with the engine and associated codes.
Spark plugs and ignition coils
Check firstWorn electrodes or a coil breaking down when hot cause misfires, especially under load.
Injector or fuel delivery
Check nextA clogged or low-flow injector leans out one cylinder.
Unmetered air
Check nextA leak after the MAF makes the mixture unstable and misfires irregular.
Other possible causes
Low compression / valve timing
Case-dependentA burnt valve, worn rings or a jumped chain keeps the misfire on the same cylinder.
All causes in the technical record
Some causes overlap with the shortlist above; this is not a probability ranking.
- Spark plugs, coils or ignition supply faults on petrol engines.
- Inadequate fuel delivery, contaminated fuel or injector problems.
- Intake leaks and other air/fuel-metering faults.
- Uneven compression, incorrect timing or position-signal problems requiring assessment.
How to test — practical steps
Start with simple checks before buying parts. This is not a VIN-specific workshop procedure; keep clear of moving parts, fuel pressure and energized circuits.
- 1
Check whether you must stop immediately
Stop safely for a flashing engine light or severe shaking; do not keep driving to reproduce misfire.
- 2
Save codes and operating conditions
Save all codes and freeze-frame data, recording temperature, load and recent work.
- 3
Identify affected cylinders in the scanner
Review cylinder misfire counters to distinguish a shared fault from one concentrated on a cylinder.
- 4
Inspect ignition parts with the engine off
On petrol engines inspect ignition, connectors and plug wells for oil/water; do not touch live high-voltage circuits.
Detailed tests / equipment needed (advanced)
Perform only tests for which you have the correct wiring diagram, equipment and training.
Locate the misfiring cylinder
You need:Scan tool with misfire countersSpark plug socket
- Read the per-cylinder misfire counters in live data, at idle and at 2,000 rpm.
- Note the cylinder with the most misfires and whether the count rises with load.
- With the engine switched off and cool, a technician may compare or swap identical coils or plugs only when the OEM procedure permits it.
- If a repeatable misfire follows the part, that part becomes a suspect; verify before replacing it.
What you should see: There is no universal acceptable misfire count. A flashing check-engine light or severe misfire calls for stopping driving and prompt diagnosis.
Never remove spark plugs on a hot engine — you risk damaging the head threads.
Run a compression test
You need:Compression testerSpark plug socket
- Compression testing requires safe access to plugs, disabled ignition and fueling, and the OEM procedure; use a workshop if not trained.
- Measure each cylinder using the temperature, throttle and cranking conditions specified by the vehicle manual.
- Compare values between cylinders and with the manufacturer specification.
What you should see: Compare absolute pressures and cylinder-to-cylinder differences against the manufacturer limits before diagnosing a mechanical fault.
Component location sketch
Full technical diagnosis — additional checks
Step-by-step diagnosis
ChecksWork through the steps before replacing parts. Adapt the checks to the manufacturer’s procedure.
Stop safely for a flashing engine light or severe shaking; do not keep driving to reproduce misfire.
Save all codes and freeze-frame data, recording temperature, load and recent work.
Review cylinder misfire counters to distinguish a shared fault from one concentrated on a cylinder.
On petrol engines inspect ignition, connectors and plug wells for oil/water; do not touch live high-voltage circuits.
Check mixture, fuel pressure and intake sealing; use engine-specific injection tests for diesels.
If electrical and fuel checks are sound, investigate compression and timing. Verify misfire repair before judging any catalyst-efficiency code.
Components to check
This list does not confirm failed components and is not a replacement recommendation. Verify the fault cause and vehicle applicability first.
- Spark plugs, coils and ignition circuit — only where fitted.
- Injectors, fuel supply and intake pipes — inspect.
- Position sensing and engine mechanical components — according to test results.
Make- and engine-specific notes
Documented configurations, not proven common defects for all makes or engines. Selecting a vehicle narrows the results.
Context guides without confirmed OEM exceptions
These explain the code for named vehicle configurations, without proving a part is defective or a cause is more common.
Notes are diagnostic leads, not proven faults or disassembly instructions. Do not work on brakes, fuel systems or hot components without proper training.
Check the fuses before ordering a part
An OBD code describes a detected condition; it does not tell you which part to replace. Start with the fuse for the affected circuit.
If the fuse is good, carry on like this:
- Check the relevant supplies and connectionsWhere the diagnostic procedure calls for electrical checks, verify supply, ground and connectors under the manufacturer’s activation conditions.
- Run the specified component testUse the manufacturer’s test for this code and component before deciding it has failed.
- Order only after the fault is demonstratedReplace a part only when the prescribed tests identify it as defective.
Check details
- Identify the circuit and any relevant fuse: Confirm the vehicle, engine, code meaning and stored operating conditions first. A fuse link is a location aid, not evidence that the fuse caused this code. Use the specified type and rating; do not repeatedly replace a fuse that opens.
- Check the relevant supplies and connections: Use the specified engine state, circuit conditions and expected values. Have live measurements performed by someone qualified. For non-electrical faults, follow the relevant mechanical, fluid, pressure or leak checks instead.
- Run the specified component test: Do not apply a generic resistance range. Any resistance or continuity test requires a de-energized circuit and an isolated component, with the correct pins and temperature from the procedure. Some components need a different kind of test.
- Order only after the fault is demonstrated: If results are normal, continue the relevant wiring, control, mechanical or intermittent diagnosis. Check for related faults and verify the repair under the required conditions. A code or a completed checklist alone does not justify replacement.
If the procedure involves airbag/SRS, pretensioners or a high-voltage system, stop DIY testing and use qualified service. Do not probe these circuits with a multimeter.
Fuses to check for this code
P0300 · Associations from the imported catalog
Confirm the model, year and engine. Associations come from the imported catalog; a code alone does not prove a blown fuse. Check machine-translated descriptions against the vehicle manual. Use the exact rating specified by the manufacturer when replacing a fuse.
854 / 854 associations found
Acura
Acura Csx 2006 2011
1815 A- Box / group
- Assignment of the fuses in the engine compartment
- Circuit / component
- ECM/PCM, Ignition Coils
Acura
Acura Ilx From 2013
M4Not specified- Box / group
- Assignment of the fuses and relay in the engine compartment (relay box)
- Circuit / component
- Ignition Coil Relay
Acura
Acura Ilx Hybrid From 2013
M4Not specified- Box / group
- Assignment of the fuses and relay in the engine compartment (relay box)
- Circuit / component
- Ignition Coil Relay
Acura
Acura Integra 2000
2915 A- Box / group
- Assignment of the fuses in the passenger compartment
- Circuit / component
- Ignition Coil
Acura
Acura Integra 2001
2815 A- Box / group
- Assignment of the fuses in the passenger compartment
- Circuit / component
- Ignition Coil
5 / 854 associations shown
Vehicle experiences and cases
User-reported cases published after moderation. Approval does not verify the diagnosis; the same code can have different causes.
No experiences have been published for this definition yet. You can be the first to share the checks and outcome.
See all vehicle experiencesManuals, components and vehicle guides
Find the relevant procedure in the workshop manual for your vehicle. A fault code alone does not identify a failed part, powertrain or exact schematic.
Vehicle guides covering this code
These vehicles have authored contextual guides; this is not a highest-risk ranking. Confirm generation and engine code before using the procedures.
Manuals open at their original source. Exact diagram availability depends on the build year, engine and manufacturer access.
System and diagnostic diagrams
Conceptual illustrations of the system; verify the actual configuration and tests in vehicle-specific documentation.
Misfire and cylinder combustion
Illustrative petrol-engine ignition example. Original conceptual diagram, not an exact component location or an OEM repair procedure.
View full-size diagram →Can I fix it myself?
Once the cause is confirmed, open the job sheet: difficulty, time, tools, parts and steps. Common jobs for P0300:
How to fix P0300: step-by-step guide
Symptoms, causes, visual inspection, scan-tool or multimeter tests, replacement and clearing the code, with safety warnings.
Irregular combustion and misfire
General system guidance · not a confirmed diagnosis
Misfire may arise from ignition, fuelling or mechanical condition. Confirm cylinder numbering for the exact engine.
The association is based on the imported description. This information explains the system; it does not confirm a procedure for the exact code, model or engine. Verify applicability in manufacturer documentation.
Checks for this type of system
- Save codes and compare affected cylinders.
- Check spark ignition only on engines equipped with it.
- Separate injection, intake and compression concerns through workshop tests.
Useful diagnostic data, where available
- Per-cylinder misfire counts where supported.
- Fuel trims and occurrence conditions.
Normal values and thresholds vary by vehicle and are not assumed here.
Mistakes to avoid
- Not every misfire is a failed coil.
- Do not apply spark-plug tests to diesels.
System-guide sources
References support general principles, not individual verification of every associated code.
Vehicle associations in the catalogue
Catalogue associations help searching and do not confirm code applicability for every model, year and engine combination. Check the vehicle service information.
Make
Model
Year
Engine
Continue your research
Links to related systems, warning lights and vehicle examples.
Similar codes
General code
Cylinder 1 misfire detected
Engine & powertrain · Cylinder combustion
General code
Cylinder 2 misfire detected
Engine & powertrain · Cylinder combustion
General code
Cylinder 3 misfire detected
Engine & powertrain · Combustion / misfires
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