P0302 on 2021-2025 Ram 1500: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2021-2025 Ram 1500

For the 5th generation Ram 1500 (2019+), P0302 isn't always a simple case of a bad spark plug or coil. Ram has issued multiple Technical Service Bulletins (TSBs) for this year range related to misfires (including P0302) that occur specifically during cold starts. These issues are often tied to the engine's complex warm-up and catalyst heating software, and the official fix is a PCM software update performed by a dealer, not a parts replacement. [TSB #18-031-25 REV. A, TSB #18-021-26] More critically, on the 5.7L HEMI engine, a persistent P0302 code is frequently an early symptom of the infamous 'Hemi tick,' which signifies a failing lifter and subsequent damage to the camshaft. This is a well-documented mechanical vulnerability requiring extensive and costly repairs.

Diagnostic Flowchart

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

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Reduced engine power
• Flashing Check Engine Light
• Decrease in fuel economy
• Engine stalling
• Audible ticking noise from the engine bay, especially on 5.7L Hemi models (potential lifter failure)

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Coil-on-plug systems are common failure points on modern engines. Heat and vibration can cause the coil's internal windings to fail over time, preventing a strong spark.
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder (e.g., cylinder 4 on a Hemi, or cylinder 4 on a V6). Clear the codes and drive the vehicle. If the code changes to P0304, the ignition coil is faulty. This is the most common first diagnostic step mentioned by owners.
   Typical fix: Replace the faulty ignition coil. While you can replace just one, if the vehicle has high mileage and original coils, replacing them all as a set can prevent future misfires.
   Est. part cost: $40-$90
2. Worn or Fouled Spark Plug 🔴 High Probability Spark plugs are a regular maintenance item. The 5.7L HEMI uses two plugs per cylinder, increasing the chance of a failure. Plugs can become worn, cracked, or fouled with oil or carbon deposits, leading to a weak or inconsistent spark.
   How to confirm: Remove the spark plug(s) from cylinder 2 and inspect for wear (worn electrode), damage (cracked porcelain), or deposits (black soot, oily residue). Compare it to a new plug. You can also swap it with another cylinder's plug to see if the misfire code follows.
   Typical fix: Replace the spark plug(s) in cylinder 2. It is best practice to replace all spark plugs at the same time for even performance and to reset the maintenance schedule.
   Est. part cost: $5-$25 per plug
3. PCM Software Update Needed 🟡 Medium Probability As documented in TSBs #18-031-25 REV. A and #18-021-26, software calibrations for cold start strategies can cause false misfires to be detected, particularly during catalyst warm-up.
   How to confirm: This can only be confirmed by a Ram dealership. If the misfire only occurs on a cold start (e.g., within the first 30 seconds) and disappears when the engine is warm, and plugs/coils are good, this is the likely cause. The TSB specifies checking freeze-frame data for low engine temp and short run time when the code set.
   Typical fix: A technician will reprogram the Powertrain Control Module (PCM) with updated software. This is a dealer-only fix.
   Est. part cost: $0 (if under warranty) - $200
4. Faulty Fuel Injector 🟡 Medium Probability Fuel injectors can become clogged with deposits from fuel or fail electronically, preventing the correct amount of fuel from being delivered to cylinder 2.
   How to confirm: An advanced diagnostic step is to swap the fuel injector from cylinder 2 with another cylinder. If the misfire code follows the injector, it is faulty. A mechanic can also perform a resistance test on the injector or use a scan tool to perform an injector balance test.
   Typical fix: Replace the faulty fuel injector. It's also wise to inspect the fuel rail and consider a professional fuel system cleaning service.
   Est. part cost: $70-$150

Rare But Worth Checking

• Engine Mechanical Failure (Lifter/Camshaft): On the 5.7L HEMI, this is a distressingly common and serious failure. A ticking noise, often called the 'Hemi tick,' is the classic symptom. A roller on a hydraulic lifter can seize, causing the lifter to stop rotating and grind a flat spot on the camshaft lobe. This results in the valve for that cylinder not opening correctly, causing a persistent misfire like P0302. Many forum threads start with a single cylinder misfire and end with a diagnosis of a failed cam and lifters, requiring major engine work.
• Intake Manifold Gasket Leak: A vacuum leak near the cylinder 2 intake runner can lean out the air/fuel mixture enough to cause a misfire. This would often be accompanied by a lean code (P0171 or P0174). A mechanic can perform a smoke test to pinpoint the source of the leak.
• Low Cylinder Compression: A burnt valve, damaged piston, leaking piston rings, or a leaking head gasket can cause a loss of compression, leading to a misfire. This is a serious mechanical issue requiring a compression test and possibly a cylinder leak-down test to diagnose.

Diagnosis Steps

1. Read the code with an OBD-II scanner and confirm P0302 is present. Note any other codes and check freeze-frame data to see when the misfire occurred (e.g., cold start, high RPM).
2. Listen to the engine. Is there a distinct, rhythmic ticking noise ('Hemi tick')? If so, suspect a potential lifter/camshaft issue, which is a common and serious problem on the 5.7L Hemi.
3. Locate cylinder 2. This is critical as it differs by engine: On the 5.7L HEMI V8, it is the front-most cylinder on the passenger side (right bank). On the 3.6L Pentastar V6, it is the front-most cylinder on the *driver's* side (left bank).
4. Swap the ignition coil from cylinder 2 with the coil from cylinder 4 (the next one back on the same side). Clear the codes and drive. If the code returns as P0304, the coil is bad.
5. If the code remains P0302, swap the spark plug(s) from cylinder 2 with cylinder 4. Clear codes and drive. If the code moves to P0304, the spark plug was the issue.
6. Inspect the wiring connector for the ignition coil and fuel injector on cylinder 2 for any damage, corrosion, or loose connections.
7. If the misfire only occurs on cold starts and the above steps don't identify the problem, consult a dealer regarding the PCM software update TSBs.
8. For more advanced diagnosis, consider swapping the fuel injector or performing a cylinder compression and leak-down test to rule out mechanical issues like bad rings, valves, or a failed head gasket.

Parts You'll Likely Need

• Ignition Coil (OEM #56028138AF (example, verify by VIN)) — This is one of the most common failure items for a single-cylinder misfire. It's responsible for generating the high voltage for the spark plug.
  Trusted brands: Mopar, NGK, Delphi
  OEM price range: $60-$100
  Aftermarket price range: $40-$80
• Spark Plug (OEM #SP143877AA (for 5.7L HEMI, verify by VIN)) — Spark plugs are a maintenance item that wear out over time, leading to a weak or inconsistent spark. The Hemi uses two per cylinder.
  Trusted brands: Mopar, NGK, Champion
  OEM price range: $15-$25
  Aftermarket price range: $5-$15
• Fuel Injector (OEM #05036333AC (example, verify by VIN)) — A clogged or failed fuel injector will starve the cylinder of fuel, causing a misfire.
  Trusted brands: Mopar, Bosch
  OEM price range: $100-$180
  Aftermarket price range: $70-$120

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or starting to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0302.
• P0171 / P0174 — If the misfire is caused by a vacuum leak affecting cylinder 2, the entire engine bank may run lean, triggering a 'Fuel System Too Lean' code for Bank 1 (P0171) or Bank 2 (P0174). [TSB #1814522]
• P0202 — This code indicates a malfunction in the cylinder 2 injector circuit. If you see P0202 with P0302, the problem is almost certainly with the fuel injector for cylinder 2 or its wiring harness.

Technical Service Bulletins (TSBs) & Recalls

• 18-031-25 REV. A: Addresses cold start misfires and advises a potential PCM reprogram.
• 18-021-26: Notes P0302-00 may be set during cold start catalyst heating.
• 09-011-25: Lists P0302 as a potential DTC for MIL illumination.
• 1800624: Lists P0302 as a potential DTC found during diagnosis.

Platform-Specific Known Issues

• Cold Start Misfires (Software Glitch):: TSB #18-031-25 REV. A and #18-021-26 specifically address misfire codes (P0300-P0306) that set dur

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (3.6L Pentastar) — expected: Approximately 12.0 - 12.4 Ohms. Failure: A significantly different reading, such as double the resistance (24 Ohms) or an open circuit (infinite resistance), indicates a failed injector.
• Fuel Injector Resistance (5.7L Hemi) — expected: Approximately 11.8 Ohms at room temperature.. Failure: Readings significantly higher or lower, or an open/short circuit, indicate a faulty injector.
• Ignition Coil Primary Resistance (5.7L Hemi) — expected: 0.558 - 0.682 Ohms at 70-80°F.. Failure: A reading outside of this range suggests the coil's primary winding is faulty.
• Ignition Coil Control Circuit Resistance — expected: Below 5.0 Ohms. Failure: Resistance above 5.0 Ohms indicates an open circuit or high resistance in the wiring between the PCM and the ignition coil.

Wiring & Ground Locations

• Cylinder Head to Firewall Ground Strap — Located at the rear of the cylinder heads. A strap connects the two heads and then grounds to the firewall via a small clip.. A missing, loose, or corroded main engine ground strap can cause a host of electrical problems, including erratic sensor readings and weak ignition spark, which can lead to misfires. One owner found this strap disconnected on his 5.7L Hemi.
• Cylinder 2 Fuel Injector Control Wire — On a 5.7L Hemi, the control wire for the cylinder 2 injector is typically Brown/Dark Blue. This wire runs from the injector connector back to the PCM connector.. When diagnosing a persistent P0302 with a P0202, a technician needs to test the continuity of this specific wire from the PCM to the injector to rule out a wiring harness break or short.
• Battery Negative Terminal Grounds — Two ground wires are typically located near the battery's negative terminal.. These are primary grounds for the entire vehicle electrical system. Corrosion or looseness here can cause system-wide low voltage issues, potentially contributing to misfires.

Real Owner Repair Stories

• Reddit user in r/ram_trucks (2017 Ram 1500 Rebel, 5.7L Hemi, 40,300 miles) — Check Engine Light with code P0302.
  ❌ Tried (didn't work) Swapping ignition coils (code remained P0302), Changing all spark plugs
  ✅ What actually fixed it The user was advised to use an automotive stethoscope on the valve cover above cylinder 2 to listen for noise. The implication, based on the conversation, is a suspected internal mechanical issue like a lifter or rocker arm, which is the next logical step after ignition components are ruled out.
• YouTube video / Mechanic diagnosis (2012 Minivan with 3.6L Pentastar V6) — P0302 misfire code along with an audible ticking noise from the engine.
  ❌ Tried (didn't work) Replaced spark plug on cylinder 2, Replaced ignition coil on cylinder 2, Swapped coils between cylinders, Swapped fuel injectors between cylinders
  ✅ What actually fixed it After all ignition and fuel-related swaps failed, a compression test was performed which showed low compression on cylinder 2. The root cause was a failed rocker arm, which prevented the valve from opening correctly, leading to the misfire. This is a known issue on Pentastar engines.
• Reddit user in r/ram_trucks (2016 Ram 1500, 3.6L V6, 70,000 miles) — P0302 code, misfire felt only at idle.
  ❌ Tried (didn't work) Mechanic replaced spark plugs and coils.
  ✅ What actually fixed it Unresolved, but highly indicative of a serious issue. The dealer quoted $900 just to tear down the engine for diagnosis, with an estimated repair cost of $4,000-$7,000 if it included new rocker arms, lifters, or camshafts. This highlights the progression from a simple code to a major mechanical repair when basic fixes fail.

OEM Part Supersession History

• 56028138AB, 56028138AD, 56028138AE → 56028138AF — Standard part revision and improvement over time.
  Heads up: The newer part number 56028138AF replaces the previous versions and should be used for service.