What this code means
P0302 generally means the PCM has detected a possible misfire contribution problem on cylinder 2.
What the vehicle may do
- The vehicle may run rough, stumble, idle unevenly, or feel down on power.
- The MIL may illuminate or flash depending on misfire severity.
- Stop/start, if equipped, can be disabled while the fault is active.
Possible fault areas
- Possible fuel delivery concerns may be involved.
- Ignition components or ignition control wiring may be involved.
- Air leaks, oiling concerns, mechanical issues, or carbon accumulation can be possible contributors.
- VVL or VVT-related operation may be involved on equipped vehicles.
- Connector, harness, PCM power or ground, or PCM control issues may be possible.
Diagnostic path
Opening context
P0302 is a cylinder 2 misfire fault. In plain terms, the PCM has seen crankshaft speed variation that points to cylinder 2 not contributing evenly. The driver may feel a rough idle, stumble, lack of power, or see the MIL illuminate or flash. On this Ram 1500DT with the 3.6 Pentastar, the broad possible fault areas can include fuel delivery, ignition, intake air leaks, oiling or mechanical issues, VVL or VVT-related operation if equipped, wiring, connectors, or PCM control. Start with the basic system checks, then follow a structured diagnostic approach instead of jumping straight to parts.
Monitor gates and code behavior
Before judging the test results, reproduce the operating conditions. Treat the enable criteria as monitor gates: fuel level above 12%, battery voltage above 10.9 volts, ambient temperature above -23°C (-9.4°F), coolant temperature at engine start above -7°C (19.4°F), or the monitor enabling when engine temperature reaches 21°C (69.8°F) if the start temperature is below threshold. Engine speed is between approximately 400 rpm and 6200 rpm, and the misfire monitor is disabled during a Decel Fuel Shutoff Event. The PCM sets this fault when crankshaft speed variation between cylinders exceeds a calibrated value based on speed and load. Depending on severity, the MIL can illuminate or flash, and during a severe flashing-MIL misfire the PCM can shut off the affected cylinder’s injector for a calibrated number of engine revolutions to help protect the catalyst. If stop/start is equipped, it is disabled while this fault is active.
Confirm the misfire is active
Turn the ignition on, then read and record all codes and captured operating data. Drive or operate the vehicle under the same captured conditions that were present when the code set. During the road test, pay attention to when the misfire happens, because that detail matters later. Watch the downstream O2 sensors while the misfire is occurring, and use the misfire monitor to confirm which cylinders are counting misfires. If cylinder 2 is showing excessive misfires right now, keep going. If it is not active, treat it as an intermittent condition and do not force the rest of the test path as if the fault is present.
Check for other direction first
Next, look at the recorded codes and any applicable bulletins. If other active or pending faults point toward fuel, ignition, air handling, VVL, or VVT operation, handle the applicable diagnostic path first. Those faults can explain the misfire or change the direction of the test. If nothing else is steering the diagnosis, move into the misfire checks.
Baseline inspection
Now do a careful diagnostic inspection. Look for belt and accessory drive problems, pulley misalignment or binding, sensor mounting issues, poor connector or terminal contact at the crank sensor, cam sensor, MAP sensor, throttle body, injector, ignition coil, and related components. Also check PCM power and ground condition, vacuum leaks, intake or exhaust restriction, internal engine concerns, moisture on ignition components, fuel level and quality concerns, and operating conditions like bogging or overload. If you find a real problem, repair it as needed, then verify the repair and confirm the code stays gone. If the inspection is clean, continue.
Oil and mechanical condition
Check engine oil level and condition before going deeper. The diagnostic path calls out oiling and mechanical concerns such as mechanical tolerances out of spec, oil pressure out of spec, low oil level, the wrong oil filter, deteriorated or dirty oil, contaminated oil, incorrect viscosity, or aerated oil. If one of those conditions is present, repair the oiling or mechanical issue, then verify the repair and confirm the code stays gone. If not, continue to the intake check.
Intake leaks and fuel quality
Check the engine and intake manifold for vacuum leaks. If an intake leak is found, repair it and verify the repair. If the intake system checks out, move to fuel quality. Check for water in the fuel, correct fuel type, old or contaminated fuel, and low fuel. Also perform the proper ethanol level check for the gasoline. If fuel quality is the problem, replace the fuel and, if necessary, flush and clean the fuel system, then verify the repair. If fuel checks out, continue to the injector balance direction.
Fuel injector comparison
Before any fuel system testing or service, release fuel system pressure. The fuel system stays under pressure even with the engine off, so do not skip that safety step. Install the Fuel Pressure Decay Tester 8978A to the fuel rail. Turn the ignition on, let fuel pressure reach maximum and stabilize, then record the starting pressure. Use the scan tool to actuate the injector for the misfiring cylinder while watching the gauge, and record the ending pressure. After each injector actuation, start the engine to clear fuel from the cylinder; skipping that can damage the engine. Repeat the same comparison on several known-good cylinders, starting from the same starting pressure. If the ending pressures are about the same, continue. If cylinder 2 stands out, a small pressure drop sends you toward debris in the fuel rail or injector, and a large pressure drop points toward a faulty or fouled injector. Repair as directed, then verify the repair and confirm the code stays gone.
VVL system check if equipped
If the vehicle is not equipped with VVL, skip this portion. If it is equipped, turn the ignition on and run the VVL system diagnostic test with the scan tool. Do not erase the code before running that routine. Follow the scan tool directions and compare the result to the VVL failure direction. A rocker arm stuck in low lift can show up as a misfire at higher engine speeds, above approximately 4000 rpm. If the routine does not show the VVL system causing the misfire, continue to ignition spark testing. If the routine points into the VVL path and calls for cylinder head oil pressure testing, go there next; if the return point is not clear, pause, recheck the earlier diagnostic path, and avoid guessing.
Cylinder head oil pressure to the VVL solenoid
For the VVL oil pressure check, turn the ignition off and remove the VVL solenoid identified by the scan tool. Install Kit, VVL Adapters 2027300090 in place of that solenoid. Start the engine and let it idle while monitoring Dual Oil Pump mode on the scan tool. Let the engine run long enough for the pump to switch to low pump mode, then record the gauge reading and compare it to the main engine oil pressure reading from the engine oil pressure sensor. Cylinder head oil pressure should be within 5.0 psi of main engine oil pressure. If it is within range, inspect the VVL solenoid screen for debris and inspect the seals for damage and correct installation. If no debris is found and the seals look good, replace the VVL solenoid, then verify the repair. If cylinder head oil pressure is not within range, diagnose and repair the lack of oil pressure to the VVL solenoid, then verify the repair.
Spark output at the coil
Before moving to ignition testing, turn the ignition off, remove the fuel pressure decay tester, and reconnect the fuel lines. Remove the ignition coil from the misfiring cylinder, reconnect the coil harness connector, and disconnect the fuel injector harness connector for the cylinder being tested. Install a spark tester on the coil. While cranking, watch for spark. If you have a crisp blue spark, continue to plug and cylinder inspection. If you do not, move to the ignition coil power and control circuit tests.
Spark plug, cylinder, compression, and plug swap
With the ignition off, remove the spark plug from cylinder 2 and inspect it for cracks, carbon tracking, oil, coolant, excess fuel, gap out of specification, or a loose or broken electrode. Also look for oil or coolant in the cylinder. If any of those conditions are present, replace the spark plug, and if oil or coolant is present, diagnose and repair that cause before verification. If the plug and cylinder inspection are clean, perform a compression test on several cylinders and compare known-good cylinders to cylinder 2. If compression is not within specification, perform a cylinder leak down test to separate valvetrain from combustion chamber concerns, repair as needed, then verify the repair. If compression is within specification, swap the spark plug with a known-good cylinder that was not misfiring, or replace the plug if access makes swapping impractical. Start the engine and watch the misfire monitor. If the misfire follows the plug, or the misfire is gone after plug replacement, complete that plug repair and verify the repair. If not, keep going.
Carbon cleaning and valvetrain inspection
Next, clean carbon from the valvetrain and combustion chambers using Mopar Combustion cleaner. After driving the vehicle and clearing the cleaner from the engine, erase the codes. Test drive the vehicle under the captured conditions, then view the misfire monitor again. If the misfire does not return, the valve and combustion chamber cleaning repaired the fault, and you still verify the repair. If the misfire returns, visually inspect the camshaft lobes, rocker arms, and springs for excessive wear or broken parts. If you find damage or wear, make the appropriate repair and verify it. If no issue is found there, move to the final harness and PCM connection checks.
Ignition coil power feed
If the earlier spark test did not show a crisp blue spark, check the ASD relay output circuit. Turn the ignition off and disconnect the ignition coil harness connector. Turn the ignition on, command the ASD relay with the scan tool, and use a 12-volt test light connected to ground at the ASD relay output circuit at the coil connector. If the light illuminates brightly, continue to the coil control circuit. If it does not, stop all scan tool actuations, repair the open or short to ground in the ASD relay output circuit between the PDC and the ignition coil connector, then verify the repair.
Ignition coil control circuit
For the coil control circuit, use a 12-volt test light connected to a 12 volt source, and back probe the coil control circuit at the ignition coil connector. Crank the engine for 5 seconds while watching the light. If the light blinks brightly, replace the ignition coil and verify the repair. If the light stays on constantly, check the control circuit for a short to ground. If the light stays off constantly, check the control circuit for an open or high resistance.
Short-to-ground and open-circuit checks
For a control circuit that stays on constantly, turn the ignition off and disconnect the PCM C2 connector. Do not probe the PCM harness connectors; use the GPEC Diagnostic 10436 adapter on the engine harness side. Check continuity between ground and the coil control circuit at the ignition coil connector. If continuity is present, repair the short to ground and verify the repair. If not, continue to the final harness and PCM connection checks. For a control circuit that stays off constantly, measure resistance in the coil control circuit between the ignition coil connector and the GPEC adapter. If resistance is below 3.0 Ohms, continue to the final harness and PCM connection checks. If it is not below 3.0 Ohms, repair the open or high resistance in the coil control circuit, then verify the repair.
Final connector and PCM path
At the end of the path, inspect the related PCM and component harness connections. Disconnect the PCM connectors, related in-line connectors if equipped, and related component connectors. Look closely for connector installation problems, damaged locks, corrosion, water intrusion, seal damage, bent terminals, overheated terminals from poor contact, terminals pushed back in the cavity, spread terminals, and poor terminal tension. Repair anything you find, then reconnect all PCM, in-line, and component connectors and make sure they are fully seated and locked. Erase the codes, then test drive or operate the vehicle under the monitored and set conditions. If P0302 returns after those checks and repairs, replace and program the PCM, then verify the repair. If it does not return, the wiring or poor connection problem has been repaired, and you still verify the repair and confirm the code stays gone.
Takeaway and CTA
The clean way through P0302 is to prove the misfire is active, rule out the supporting conditions, compare cylinder 2 against known-good cylinders, then separate fuel, ignition, VVL, mechanical, wiring, and PCM control without skipping verification. For more diagnostic training, visit stepdiagnostics.com.
Final check
A cylinder-specific misfire is often diagnosed best by confirming the active condition, comparing that cylinder to known-good cylinders, and verifying the repair after each confirmed fault path.
For more guided automotive diagnostics, visit STEP Diagnostics.
