P0302 on 2015-2020 Ram 3500: Cylinder 2 Misfire Causes and Fixes (Hemi & Cummins)

What's Unique About the 2015-2020 Ram 3500

For the Ram 3500, diagnosing a P0302 code is entirely dependent on the engine. The path for the 6.4L Hemi V8 (gasoline) is completely different from the 6.7L Cummins I6 (diesel). For the Hemi, the issue is typically spark-related but can be a symptom of a serious internal engine problem like a failed lifter, a known weakness of the Hemi engine family. For the Cummins, it's almost always fuel-related, pointing toward a bad injector or its wiring. This year range also spans two generations—the fourth (2015-2018) and the fully redesigned fifth (2019-2020)—which can have differences in parts and software, particularly with the Cummins engine which was significantly updated in 2019.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: This range covers the fourth generation (2015-2018) and the fifth generation (2019-2020). The fifth-gen was a major redesign with a new frame, interior, and upgraded powertrains. The 6.7L Cummins was significantly updated for 2019 with a new block, pistons, and higher-pressure fuel injectors, meaning some parts are not interchangeable with earlier models. While the core causes of P0302 are similar, specific part numbers and software may differ.

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Solid or flashing Check Engine Light
• Noticeable loss of engine power
• Decrease in fuel economy
• For Cummins diesel: white or black smoke from the exhaust, especially at idle.
• For Hemi gas: A persistent, rhythmic ticking or knocking sound from the engine, often called the 'Hemi tick'.

Most Likely Causes

1. 6.4L Hemi: Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems place the coil directly on the engine, exposing it to intense heat and vibration, which leads to eventual failure. This is the most common cause of a single-cylinder misfire on a Hemi.
   How to confirm: Swap the ignition coil from cylinder #2 with another cylinder (e.g., cylinder #4). Clear the codes. If the code changes to P0304, the coil is bad. Cylinder #2 is the front-most cylinder on the passenger side.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace all 8 coils and 16 spark plugs at the same time if they are high-mileage originals.
   Est. part cost: $35 - $100 per coil
2. 6.7L Cummins: Faulty Fuel Injector 🔴 High Probability → Shop Fuel Injector The high-pressure common rail fuel system operates under extreme pressure (up to 29,000 PSI in 2019+ models), leading to eventual wear and tear on injector internal components. Fuel contamination is a major contributor to premature failure.
   How to confirm: A professional scan tool can perform a cylinder contribution test or read injector balance rates to identify the weak cylinder. A return flow test can also confirm excessive internal leakage from the injector. A P0202 code appearing with P0302 is a strong indicator of an injector or wiring fault.
   Typical fix: Replace the fuel injector for cylinder #2. This is a complex job that also requires replacing the high-pressure connector tube. It is often recommended to replace all six injectors as a set if the vehicle has high mileage. A capable scan tool is needed to program the new injector's calibration code into the ECM.
   Est. part cost: $440 - $650 per new OEM Bosch injector.
3. 6.4L Hemi: Worn or Fouled Spark Plugs 🟡 Medium Probability → Shop Spark Plug The 6.4L Hemi uses two spark plugs per cylinder (16 total). Over time, the electrodes wear down or become fouled by carbon or oil, leading to a weak or inconsistent spark. Service life is typically up to 100,000 miles.
   How to confirm: Remove the two spark plugs from cylinder #2. Inspect for worn electrodes, heavy carbon buildup, oil fouling, or cracks in the porcelain. Compare them to plugs from a working cylinder. The correct gap is typically 0.043-0.044 inches.
   Typical fix: Replace the spark plugs. It is best practice to replace all 16 spark plugs at once with high-quality OEM-spec replacements.
   Est. part cost: $80 - $200 for a set of 16
4. 6.4L Hemi: Failed Lifter and/or Camshaft Lobe ⚪ Low Probability → Shop Engine Camshaft Some Hemi engines, including the 6.4L, are known to experience lifter failure where the roller bearing seizes, causing the lifter to grind against the camshaft lobe, leading to a misfire. This is often preceded by a distinct 'Hemi tick' sound and is considered a major weakness of the engine family.
   How to confirm: Listen for a persistent ticking or knocking sound from the engine, especially at idle. A mechanic can use a stethoscope on the valve cover to isolate the noise. Definitive diagnosis requires removing the valve cover and intake manifold to visually inspect the camshaft and lifters for damage, such as a roller that won't spin.
   Typical fix: This is a major and expensive engine repair that involves replacing the camshaft, all lifters (often with an upgraded design), head gaskets, and other related components.
   Est. part cost: $1000 - $2500+ for parts alone.
5. 6.7L Cummins: Injector Wiring Harness Fault ⚪ Low Probability The injector wiring is integrated into the valve cover gasket assembly. Constant heat and vibration can cause the wire for a specific cylinder to break or short out over time, causing an open circuit.
   How to confirm: Check for continuity on the injector #2 circuit between the main engine harness connector and the injector itself. A code P0202 (Injector Circuit Malfunction) is often present alongside P0302 when this is the cause.
   Typical fix: Replace the valve cover gasket assembly, which contains the new integrated injector harness. This should be done when replacing injectors to avoid future issues.
   Est. part cost: $200 - $400

Rare But Worth Checking

• PCM Software Glitch: The provided NHTSA Technical Service Bulletins (TSBs) list P0302 along with all other cylinder misfire codes (P0301-P0306) and other unrelated codes. This indicates that a software update may be required to prevent the PCM from falsely setting these codes, particularly on 2020 Cummins models per TSB 18-102-22 REV A. [Bulletin #1800824, #1800724, #1806623, #1810122REVA, 1]
• Low Compression: Although rare, a mechanical issue like a burnt valve, leaking head gasket, or damaged piston/rings can cause a lack of compression in cylinder #2, resulting in a misfire. A compression test is needed to diagnose this. On a Hemi, this can be the result of a catastrophic lifter failure.

Diagnosis Steps

1. Identify the engine in your truck (6.4L Hemi gas or 6.7L Cummins diesel), as the diagnostic steps are completely different.
2. For 6.4L Hemi: Start with the ignition system. Swap the ignition coil from cylinder #2 (front passenger side) with another cylinder (like #4, second from front on passenger side).
3. Clear the codes and drive the vehicle. If the code returns as P0304, the ignition coil is faulty and needs replacement.
4. If the code remains P0302, inspect the two spark plugs in cylinder #2 for wear, fouling, or damage. Check for a correct gap of ~.043 inches. Replace if necessary.
5. If ignition components are good, listen carefully for a persistent ticking noise from the passenger side valve cover area, which is a strong indicator of lifter/camshaft failure.
6. For 6.7L Cummins: Diagnosis typically requires a capable scan tool. Check for other codes, specifically P0202, which would indicate a wiring issue.
7. Use the scan tool to monitor injector balance rates or perform a cylinder contribution test. A high positive or negative value for cylinder #2 indicates a faulty injector.
8. If scan tool data is inconclusive, a physical injector return flow test can be performed to check for excessive internal leakage, confirming a bad injector.
9. For both engines: If all else fails, perform a compression test on cylinder #2 to rule out mechanical engine problems like a bad valve or piston rings.

Parts You'll Likely Need

• Ignition Coil (6.4L Hemi)

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or begins to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may be stored. This can happen with a failing camshaft that affects multiple lobes.
• P0202 — This code indicates a fault in the cylinder 2 injector circuit. Seeing P0202 and P0302 together strongly points to a problem with the fuel injector or its wiring, not a spark or mechanical issue.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #1800824 - Lists P0302 with other misfire codes related to ECU performance.
• Bulletin #1800724 - Lists P0302 with other misfire codes related to ECU performance.
• Bulletin #1806623 - Lists P0302 with other misfire codes related to ECU performance.
• Bulletin #1810122REVA - Lists P0302 with other misfire codes related to ECU performance.

Platform-Specific Known Issues

• 6.4L Hemi Camshaft/Lifter Failure: A P0302 code, especially when accompanied by a persistent ticking noise, can be an early symptom of a failing lifter and subsequent camshaft damage, which is a known and serious issue for this engine family.
• 6.7L Cummins Injector Harness: The wiring for the injectors is integrated into the valve cover gasket. A break in the wire for cylinder #2 can cause a P0302 code and is a cheaper fix than a full injector replacement.
• ECU Software Updates: As noted in several TSBs, the PCM may require a software reflash to correct logic that could erroneously trigger multiple misfire codes, including P0302. [Bulletin #1800824, #1800724, #1806623, #1810122REVA]

Mechanic-Grade Diagnostic Values

• 6.7L Cummins: Fuel Injector Resistance — expected: Less than 1.0 Ω, but greater than 0 Ω (measured across injector pins). Failure: An open loop (OL) reading indicates a failed injector solenoid.
• 6.7L Cummins: Injector Balance Rates at Hot Idle — expected: Typically within ±4.0 mm³/stroke. Failure: A consistent reading above +4.0 or below -4.0 on cylinder #2 suggests a faulty injector or mechanical cylinder issue. Positive values mean the ECM is adding fuel to a weak cylinder; negative values mean the ECM is cutting fuel from an over-fueling injector.
• 6.7L Cummins (2015-2018): Combined Injector Return Flow (Running Test) — expected: Less than 210 mL in 30 seconds. Failure: Flow greater than 210 mL indicates excessive leakage from one or more injectors. This test is performed using a scan tool's 'Fuel Pressure Override Test' which commands ~26,000 PSI at 1200 RPM.
• 6.7L Cummins (2015-2018): Combined Injector Return Flow (Cranking/No-Start Test) — expected: Less than 40 mL in 10 seconds of cranking. Failure: Flow greater than 40 mL indicates excessive leakage preventing the rail from building enough pressure to start.
• 6.7L Cummins: Individual Injector Contribution to Return Flow — expected: N/A. Failure: If capping off a single injector's high-pressure line reduces the total return flow by more than 40 mL, that specific injector is leaking internally and is faulty.
• 6.7L Cummins: Injector Solenoid Nut Torque — expected: 13 in-lbs (1.5 Nm). Failure: Incorrect torque can lead to a poor connection or damage to the injector. This is a very light torque value.

Scan Tool Commands That Help

• wiTECH, Autel, Snap-on, or equivalent professional scanner: Injector Quantity Adjustment (IQA) — Required after replacing a fuel injector on the 6.7L Cummins. Each new injector has a unique calibration code that must be programmed into the ECM for correct fuel trimming and smooth engine operation.
• wiTECH, Autel, Snap-on, or equivalent professional scanner: Cylinder Performance Test / Injector Kill Test — To confirm which cylinder is misfiring. The scan tool deactivates one injector at a time; the cylinder that causes the least change in engine RPM when disabled is the one that is not contributing properly.
• wiTECH or equivalent: Fuel Pressure Override Test — This function is required to perform a running injector return flow test on the 6.7L Cummins. It commands the fuel system to its maximum pressure (~26,000 PSI) at a set RPM, allowing for accurate measurement of injector leakage under stress.

Wiring & Ground Locations

• 6.7L Cummins PCM Connector C1 - Injector #2 Circuit — The PCM is located on the driver's side of the engine block. C1 is one of the large multi-pin connectors.. For advanced wiring diagnostics, the cylinder 2 injector driver circuits are on pins K12 (High Side Driver) and K612 (Low Side Driver). Technicians test for continuity and shorts between these pins and the injector harness connector.
• 6.7L Cummins Injector Harness Connectors — On the driver's side of the engine valve cover, there are two large, external, multi-pin connectors for the injector harness that passes through the valve cover gasket.. The front-most connector serves cylinders 1, 2, and 3. The rear connector serves cylinders 4, 5, and 6. Knowing which connector serves cylinder #2 is critical when diagnosing wiring faults without removing the valve cover.
• Primary Engine & Body Grounds — Key ground points include a large cable from the negative battery terminal to the front of the engine block, and a smaller wire from the negative terminal to the body, often near the driver's side headlight.. A poor engine or PCM ground can cause erratic sensor readings and misfire codes. While not a common cause for a single-cylinder misfire, it should be checked if multiple electrical issues are present.

OEM Part Supersession History

• 5038785AC, 53021726BC, 68060714AA (and others) → 05038785AD — Part has been updated by the manufacturer over time.
  Heads up: These are for the 6.4L Hemi non-MDS lifter yokes. Always verify the latest part number with a dealer based on VIN, but 05038785AD is a common replacement part.
• 5038786AC, 53021728BC, 68060715AA (and others) → 5038786AD — Part has been updated by the manufacturer over time.
  Heads up: These are for the 6.4L Hemi MDS lifter yokes.

Model Year Variations Within This Range

• 2019-2020: The 6.7L Cummins engine was significantly updated. It uses different fuel injectors than the 2015-2018 models and has two different versions: Standard Output and High Output (HO), which use different injectors from each other. High Output Injector: Bosch P/N 0 445 124 039. Standard Output Injector: Bosch P/N 0 445 124 047. Using the wrong injector will cause performance issues.