P0302 on 2015-2020 Ram 2500: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2015-2020 Ram 2500

For the 2015-2020 Ram 2500, the cause of a P0302 code is entirely dependent on which engine is in the truck. The gasoline-powered 5.7L and 6.4L HEMI V8s most often have ignition-related misfires from simple wear items like coils and spark plugs. However, these HEMI engines are also known for a specific type of lifter failure that can lead to a persistent misfire, often accompanied by a distinct ticking sound known as the 'Hemi tick'. In stark contrast, the 6.7L Cummins diesel engine's misfires are almost exclusively due to fuel system problems, with the fuel injector for cylinder #2 being the primary suspect. The wiring harness for the Cummins injectors, which passes through the valve cover gasket, is also a known failure point due to heat and vibration.

Diagnostic Flowchart

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

Generation note: The 2015-2020 year range covers two generations of the Ram 2500. The fourth generation (DJ) was produced until the 2018 model year, and the fifth generation (DT) began with the 2019 model year. While the primary engine options (6.4L HEMI, 6.7L Cummins) were carried over, there may be differences in electronics and specific part numbers between generations. For Cummins engines, several TSBs involving PCM software updates are year-specific. The diagnostic approach for P0302 remains very similar for both generations.

Symptoms You May Notice

• Solid or flashing Check Engine Light
• Rough idle or shaking engine
• Hesitation or stumbling during acceleration
• Noticeable loss of power
• Increased fuel consumption
• Fuel smell from the exhaust
• Audible rhythmic ticking sound from the engine bay (HEMI engines, indicates potential lifter failure)

Most Likely Causes

1. Faulty Ignition Coil (HEMI Engines) 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are a common failure point on most modern gasoline engines due to constant exposure to high heat and vibration in the engine bay.
   How to confirm: Swap the ignition coil from cylinder #2 with another cylinder (e.g., cylinder #4). Clear the codes and drive. If the code changes to P0304, the coil is bad. This is a definitive and free diagnostic step.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace the spark plugs at the same time, especially if they are near their service interval.
   Est. part cost: $35-$100
2. Worn or Fouled Spark Plugs (HEMI Engines) 🔴 High Probability → Shop Spark Plug HEMI engines use two spark plugs per cylinder (16 total), increasing the chances of a single plug failing. Spark plugs are a regular maintenance item and will eventually wear out. The service interval is typically 100,000 miles.
   How to confirm: After confirming the coil is good, remove and inspect the spark plugs from cylinder #2. Look for heavy carbon buildup, oil fouling, a worn-out electrode, or cracks in the porcelain.
   Typical fix: Replace the spark plugs. It's best practice to replace all 16 plugs at once to ensure consistent performance. Apply a small amount of anti-seize to the threads and dielectric grease to the inside of the coil boot.
   Est. part cost: $50-$150 for a full set
3. Faulty Fuel Injector (6.7L Cummins Diesel) 🔴 High Probability → Shop Fuel Injector High-pressure common rail diesel injectors operate under extreme stress and are the most common cause of a single-cylinder misfire on the 6.7L Cummins.
   How to confirm: Use a high-end scan tool to perform an injector cutout test, which deactivates each injector one by one to see which one has no effect on engine RPM. A professional diagnosis is recommended. Before replacement, check for PCM software updates via TSBs.
   Typical fix: Replace the faulty fuel injector and the corresponding high-pressure connector tube. It is highly recommended to use OEM Bosch or Cummins parts and replace the connector tube at the same time to prevent leaks and warranty issues. The injector hold-down bolts should be torqued to 71 in-lb.
   Est. part cost: $300-$600 per injector
4. Camshaft/Lifter Failure (HEMI Engines) 🟡 Medium Probability → Shop Engine Camshaft The 5.7L and 6.4L HEMI engines are known for potential failures of the roller lifters, which can seize and damage the camshaft lobes. This often starts as a distinct ticking sound and can lead to a persistent misfire code like P0302.
   How to confirm: Listen for a persistent, rhythmic ticking sound from the engine, especially at idle. A compression test or a physical inspection by removing the valve cover and intake manifold is required for definitive diagnosis. If the issue is caught early, the cam may be salvageable, but continued driving will destroy the engine.
   Typical fix: This is an extensive and expensive repair requiring replacement of the camshaft, all 16 lifters, head gaskets, and associated components. A shop repair can cost between $4,000 and $7,500.
   Est. part cost: $1000-$2500+

Rare But Worth Checking

• Faulty Fuel Injector (HEMI Engines): → Shop Fuel Injector While less common than coils or plugs on the HEMI, a clogged or failed fuel injector can cause a misfire. TSB 14-003-22 REV. A was issued for some 2021 6.4L vehicles for high-flow injectors causing misfires.
• Intake Manifold Gasket Leak: → Shop Engine Intake Manifold A vacuum leak near the cylinder #2 intake runner can lean out the air/fuel mixture and cause a misfire. This is more likely to cause multiple misfire codes but can be isolated to one cylinder.
• Low Compression: Internal engine issues like a burnt valve, worn piston rings, or a damaged cylinder head can cause a loss of compression and a persistent misfire. A dropped valve seat is also a known, though less common, issue on some HEMI engines.
• VVT Solenoid Failure (HEMI Engines): A faulty Variable Valve Timing (VVT) control solenoid for cylinder 2 can cause it to become stuck, leading to a misfire, sometimes accompanied by a P105D code.

Diagnosis Steps

1. Verify the code with an OBD-II scanner and check for any other stored codes.
2. Identify your engine: 6.4L HEMI V8 or 6.7L Cummins Diesel. The steps diverge significantly.
3. For HEMI V8 Engines:
4. Locate cylinder #2. On a HEMI V8, the cylinders on the passenger's side are 2-4-6-8, from front to back. Cylinder #2 is the front-most cylinder on the passenger side.
5. Swap the ignition coil from cylinder #2 with another cylinder (e.g., cylinder #4). Clear the codes and drive the vehicle. If the code returns as P0304, you have a bad ignition coil.
6. If the code remains P0302, swap the spark plugs between the same two cylinders. If the code then moves to P0304, you have a bad spark plug.
7. If the misfire is still on cylinder #2, inspect the wiring and connector for the ignition coil and fuel injector for any damage.
8. Listen for a distinct ticking noise. If present, a camshaft/lifter issue is likely and requires professional diagnosis, likely including a compression test.
9. For 6.7L Cummins Diesel Engines:
10. Check for applicable TSBs. A dealer may need to perform a PCM software update which could resolve the issue without parts replacement.
11. Locate cylinder #2. On the inline-six Cummins, the cylinders are numbered 1-2-3-4-5-6 from front to back. Cylinder #2 is the second cylinder from the front of the engine.
12. The most likely cause is the fuel injector. A professional diagnosis using a scan tool with an injector cutout test is the most effective way to confirm.
13. Inspect the wiring harness going to the fuel injectors, especially where it passes through the valve cover gasket, for any signs of chafing or damage.
14. If replacing the injector, also replace the high-pressure connector tube and torque the injector hold-down bolts to 71 in-lbs.

Parts You'll Likely Need

• Ignition Coil (HEMI Engines) (OEM #68238603AA) — This is the most common failure item for a single-cylinder misfire on the HEMI engines. This part number supersedes 56029129AF and 68060346AA.
• Spark Plugs (6.4L HEMI) (OEM #SP138239AC) — Spark plugs are a primary cause of misfires and are a regular maintenance item. The 6.4L HEMI uses 16 plugs.
• Spark Plugs (5.7L HEMI) (OEM #SP143877AB) — Like the 6.4L, the 5.7L uses 16 plugs and they are a common failure point.
• Fuel Injector (6.7L Cummins, 2013-2018) (OEM #0445120187 (Bosch)) — The most common cause of a P0302 on the Cummins engine. Using genuine Bosch remanufactured or new injectors is highly recommended.
• Injector Connector Tube (6.7L Cummins) (OEM #F00RJ01572 / 3979419) — It is best practice to replace this tube when replacing an injector to prevent high-pressure fuel leaks. Using non-OEM tubes can void injector warranty.
• Camshaft & Lifter Kit (HEMI Engines) (OEM #Multiple, often sold as kits e.g., MMX NSR MDS Camshaft Kit) — For a persistent P0302 with a ticking noise, a failed lifter and damaged camshaft is a probable cause requiring a full replacement kit.

Related Codes That Often Appear With This One

• P0300 — If the misfire condition is intermittent or affects multiple cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0302.
• P0202 — This code means "Injector Circuit/Open - Cylinder 2". If you see P0202 along with P0302, the problem is almost certainly with the cylinder 2 fuel injector or its wiring, not an ignition or mechanical issue.
• P0301, P0303, P0304, etc. — If other cylinder-specific misfire codes are present, it points towards a systemic issue like a faulty PCM software flash, low fuel pressure, or a failing camshaft affecting multiple cylinders.

Technical Service Bulletins (TSBs) & Recalls

• TSB #18-102-22 REV A: For 2020 Ram 2500/3500 with the 6.7L Cummins, this bulletin involves a PCM software update to fix a long list of potential codes, including P0301 through P0306 misfires. It also addresses symptoms like idle instability.
• TSB #18-066-23: Supersedes the above TSB for 2020 models, providing further software enhancements for the 6.7L Cummins PCM to correct issues that could set a P0302 code.
• TSB #18-101-22 REV A: Similar to the 2020 TSB, this one applies to 2019 Ram 2500/3500 trucks with the 6.7L Cummins and lists P030x misfire codes as being potentially resolved by a PCM software update.
• TSB #14-003-22 REV. A: Applies to 2021 vehicles with the 6.4L HEMI engine, including the Ram 2500 platform mates (Challenger, Durango, Grand Cherokee), for misfire codes P0300-P0307 caused by a batch of high-flowing fuel injectors.

Platform-Specific Known Issues

• HEMI Camshaft and Lifter Failure: The 5.7L and 6.4L HEMI engines in this generation are susceptible to a failure of the roller lifters, which can then damage the camshaft. This often begins as an audible 'tick' and can eventually cause a persistent misfire code like P0302. The repair is invasive and expensive.
• Cummins Injector and Harness Issues: On the 6.7L Cummins, single-cylinder misfires are almost always traced back to the fuel injector for that cylinder. The high-pressure injectors are a common wear item.

Mechanic-Grade Diagnostic Values

• 6.7L Cummins Fuel Injector Resistance — expected: Less than 1.0 ohm, and greater than 0 ohms. Failure: A reading of 0 ohms indicates a short; an infinite or high reading indicates an open circuit.
• 6.7L Cummins Fuel Rail Pressure (at idle) — expected: 6,800 - 7,000 PSI. Failure: Significantly lower pressure suggests a weak lift pump, clogged filters, or a failing high-pressure pump.
• 6.7L Cummins Injector Return Flow (Running) — expected: Maximum of 210 mL in 30 seconds for all injectors combined.. Failure: Total flow exceeds 210 mL, or blocking off one injector's return line reduces total flow by more than 40 mL, indicating excessive leakage from that injector.
• 6.7L Cummins Injector Hold-Down Bolt Torque — expected: 71 in-lbs (8 Nm). Failure: Incorrect torque can cause compression leaks or damage the injector.
• HEMI Ignition Coil Primary Resistance — expected: 0.49 - 0.57 ohms. Failure: A reading outside this range indicates a faulty coil winding.
• HEMI Ignition Coil Control Circuit Resistance — expected: Below 5.0 ohms. Failure: Resistance above 5.0 ohms indicates an open or high resistance in the wiring between the PCM and the ignition coil.

Scan Tool Commands That Help

• wiTECH, Autel, AlfaOBD: Cylinder Contribution / Cut-out Test — This is the primary diagnostic function for a P0302 on a 6.7L Cummins. It deactivates injectors one by one to identify which cylinder's power contribution is weakest, confirming a faulty injector without disassembly.
• wiTECH, Autel, AlfaOBD: Injector Quantity Adjustment (IQA) Programming — This is a required step after replacing a fuel injector on a 6.7L Cummins. The unique calibration code from the new injector must be programmed into the ECM for correct fueling and smooth operation.
• Professional Scan Tool: ASD Relay Actuation — For HEMI engines, this command forces the Auto Shutdown (ASD) relay on, allowing a technician to test for power at the ignition coil connector to rule out a power supply issue.

Wiring & Ground Locations

• Cummins Injector Harness Connector (Front) — On the driver's side of the valve cover, on top of the 6.7L Cummins engine. The front of two large connectors serves cylinders 1, 2, and 3.. This is the primary electrical connection point to test the wiring for the cylinder 2 injector. Faults often occur in the harness that passes through the valve cover gasket from this connector.
• G105 (Example Engine Ground) — Typically located on the engine block or frame rail near the front of the engine compartment.. A loose or corroded main engine ground can cause erratic behavior in sensors and actuators, including the crankshaft position sensor or injector drivers, leading to false or intermittent misfire codes.
• Main PCM Ground Stud — Varies by year, but generally found on the firewall or inner fender, sometimes near the battery.. A poor ground connection for the Powertrain Control Module (PCM) can cause a wide range of difficult-to-diagnose issues, including misfire detection problems or faulty driver circuit operation.

Real Owner Repair Stories

• RamForum.com user (2012 Ram 1500 5.7L HEMI, 112k miles) — P0302 code appeared under heavy load, accompanied by the 'Hemi tick' sound.
  ❌ Tried (didn't work) Replacing the MDS Solenoid, Replacing spark plugs
  ✅ What actually fixed it Diagnosis revealed a failed lifter and scored camshaft on cylinder 2. The valve was only opening about 15% when the engine was turned by hand. The required fix was a full camshaft and lifter replacement.

OEM Part Supersession History

• Varies → 5045517AC — Standard OEM part for 6.4L HEMI with MDS.
  Heads up: This camshaft is for the 6.4L HEMI with MDS, used in Ram HD trucks. Do not confuse with part number 5037379BC, which is for 6.4L HEMI engines WITHOUT MDS (typically found in cars like the Challenger/Charger). Installing the wrong camshaft will cause significant engine performance issues.

Model Year Variations Within This Range

• 2019-2020: The 2019 model year marked the start of the 5th generation (DT) Ram. While engines carried over, the 6.7L Cummins block was updated to compacted graphite iron (CGI), and vehicle electronics were significantly changed. This can lead to different PCM software calibrations and part numbers compared to the 2015-2018 4th generation (DJ) trucks.