P0303 on 2014-2021 Dodge Challenger: Cylinder 3 Misfire Causes and Fixes

What's Unique About the 2014-2021 Dodge CHALLENGER

For Dodge Challengers equipped with Hemi V8 engines (5.7L, 6.4L, 6.2L), a persistent P0303 code can be an early warning sign of a more serious issue: lifter and camshaft failure. This issue, often called the 'Hemi tick,' occurs when a lifter's roller bearing fails, causing the lifter to grind against and destroy the camshaft lobe. The failure is often attributed to a combination of lifter design and lubrication issues, sometimes related to the Multi-Displacement System (MDS). While standard ignition components are the most common cause, if replacing the spark plug and coil doesn't resolve the P0303 code, the possibility of this internal engine damage should be investigated immediately, especially if a ticking noise is present. An owner complaint to the NHTSA also documented a P0303 code leading to the discovery of a scored cylinder wall, a severe mechanical failure.

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
• Engine hesitation or stumbling during acceleration
• Noticeable loss of power
• Flashing Check Engine Light (especially during the misfire event)
• Increased fuel consumption
• Engine stalling
• Fuel smell from the exhaust
• Audible ticking or tapping sound from the engine (especially on Hemi V8s)

Most Likely Causes

1. Worn or Faulty Spark Plug 🔴 High Probability Spark plugs are regular maintenance items that wear out. Hemi engines use 16 spark plugs (two per cylinder), increasing the chance of a single failure. A cracked porcelain insulator or incorrect gap can also cause a misfire.
   How to confirm: Inspect the spark plug from cylinder 3 for wear, fouling (black, oily, or white deposits), or damage like a cracked insulator. Compare it to a new plug. You can also swap the cylinder 3 plug with one from another cylinder (e.g., cylinder 1) and see if the code changes to P0301.
   Typical fix: Replace the spark plug. It is recommended to replace all spark plugs on the affected bank, or all plugs on the engine, for even performance. Hemi engines require 16 plugs.
   Est. part cost: $10 - $30 per plug
2. Faulty Ignition Coil 🔴 High Probability
   How to confirm: The easiest way to test is to swap the ignition coil from cylinder 3 with a coil from an adjacent, working cylinder (e.g., cylinder 1). Clear the codes and run the engine. If the code changes to P0301, the ignition coil is bad. Visually inspect the coil for cracks or carbon tracking.
   Typical fix: Replace the faulty ignition coil. These are individual 'coil-on-plug' units and can be replaced one at a time.
   Est. part cost: $40 - $100
3. Clogged or Faulty Fuel Injector 🟡 Medium Probability
   How to confirm: Listen to the injector with a mechanic's stethoscope; it should make a consistent clicking sound. Use a 'noid' light to verify the injector is receiving an electrical pulse. Swapping the injector with another cylinder is a definitive but more labor-intensive test.
   Typical fix: Replace the faulty fuel injector. In a forum post regarding a Ram 1500 with P0303, a new fuel injector resolved the issue.
   Est. part cost: $50 - $150

Rare But Worth Checking

• Camshaft/Lifter Failure (Hemi Engines): On 5.7L, 6.4L, and 6.2L Hemi engines, a persistent misfire accompanied by a distinct ticking sound can indicate a failed lifter, which often damages the camshaft lobe. This is a significant mechanical failure requiring extensive engine work. Forum users with P0303 on Hemi vehicles frequently point to this as the root cause after ignition parts are replaced. If basic checks don't solve the P0303, this should be investigated by a professional immediately to prevent further engine damage.
• Wiring Harness/Connector Issue: The wiring harness or electrical connector for the ignition coil or fuel injector on cylinder 3 can become damaged, corroded, or chewed by rodents. This can cause an intermittent or constant misfire. A visual inspection of the harness leading to cylinder 3 is recommended. A repair might involve a new pigtail connector.
• Low Engine Compression: Internal engine damage such as a burnt valve, worn piston rings, or a damaged cylinder wall can cause a loss of compression, leading to a misfire. An NHTSA complaint for a 2015 Challenger with a P0303 code noted 'scoring on the cylinder 3 wall'. A compression or leak-down test is needed to diagnose this.
• Faulty Powertrain Control Module (PCM): In rare cases, the driver circuit within the PCM that controls the ignition coil or fuel injector for cylinder 3 can fail. TSB #18-094-16 also notes that a PCM software update may be required to correct overly sensitive misfire detection logic on some 2014 models. This should be considered after all other possibilities have been exhausted.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0303 and check 🎬 Watch: A complete guide to diagnosing and fixing P0303 misfires. for any other codes.
2. Determine the location of cylinder 3. For the 3.6L V6, it's the middle cylinder on the driver's side (front of car is 1-3-5 on passenger side, 2-4-6 on driver's side). For Hemi V8s, it's the second cylinder back on the driver's side (odd cylinders 1-3-5-7 on driver's side, even 2-4-6-8 on passenger side).
3. Swap the ignition coil from cylinder 3 with another cylinder (e.g., cylinder 1). Clear the codes and drive the vehicle. If the code changes to P0301, the ignition coil is faulty.
4. If the code remains P0303, swap the spark plug from cylinder 3 with another cylinder. If the code follows the plug, the spark plug is the issue.
5. If the misfire still persists on cylinder 3, visually inspect the wiring and connector for the ignition coil and fuel injector for any damage, corrosion, or rodent chew marks.
6. Check the fuel injector on cylinder 3. Listen for a steady clicking sound. A 'noid' light can verify if the injector is receiving a pulse from the PCM.
7. For Hemi engines, listen carefully for a ticking sound, especially on cold starts. If a tick is present with a persistent P0303, the likelihood of lifter/camshaft failure is high.
8. If ignition, fuel, and wiring check out, perform a compression test on cylinder 3 to rule out mechanical engine problems like bad valves, piston rings, or head gasket issues.
9. If a Hemi lifter/cam failure is suspected 🎬 See this detailed explanation of why Hemi lifters fail., the next step is to remove the driver's side valve cover to inspect the valvetrain for cylinder 3, checking for a collapsed lifter or worn camshaft lobe.

Parts You'll Likely Need

• Ignition Coil (OEM #68238603AA (Fits many 5.7L, 6.2L, 6.4L Hemi applications, supersedes multiple older part numbers)) — This is one of the most common failure points for a single-cylinder misfire. It's a relatively simple and quick part to replace.
  Trusted brands: Mopar, NGK, Delphi
  OEM price range: $70 - $120
  Aftermarket price range: $40 - $100
• Spark Plug (OEM #SP149212AC (For 6.4L Hemi), SPLZFR5C11 (For 5.7L Hemi), SP149125AE (For 3.6L V6)) — As a standard wear item, a fouled or worn-out spark plug is a very frequent cause of misfires.
  Trusted brands: NGK, Champion
  OEM price range: $15 - $30
  Aftermarket price range: $10 - $25
• Fuel Injector — Less common than ignition parts, but a clogged or failed injector will prevent the proper amount of fuel from reaching the cylinder, causing a misfire.
  Trusted brands: Mopar, Bosch, Standard Motor Products
  OEM price range: $100 - $200
  Aftermarket price range: $50 - $150

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or begins to affect other cylinders due to a systemic issue (like the beginning of widespread lifter failure), a P0300 (Random/Multiple Cylinder Misfire) may be stored alongside P0303.
• P0353 — This code specifically indicates a malfunction in the ignition coil primary or secondary circuit for cylinder 3. If you see this with P0303, the ignition coil or its wiring/connector is almost certainly the problem.
• P219A — This code (Bank 1 Air-Fuel Ratio Imbalance) can sometimes appear with a misfire code on Hemi engines. TSBs have been issued for other models suggesting a PCM update can resolve these codes appearing together, indicating a potential software logic issue.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #1400322REVA: Lists P0303 with other misfire codes related to the fuel system.
• Bulletin #18-094-16 & #1809416: Mentions P0303 in a list of misfire codes that can be addressed by a PCM software update for 2014 models to correct overly sensitive misfire detection.

Platform-Specific Known Issues

• On Hemi V8 engines, a P0303 code can be an indicator of a failing valve lifter, which can also damage the camshaft. This is a known issue and is often accompanied by a ticking noise from the engine, known as the 'Hemi Tick'.
• A 2015 Challenger owner reported a P0303 code that was ultimately caused by scoring on the cylinder 3 wall, requiring major

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Winding Resistance — expected: 0.75 - 0.81 Ohms. Failure: A reading significantly outside this range indicates a defective coil.
• Ignition Coil Secondary Winding Resistance — expected: 10,000 - 11,000 Ohms (10-11 kOhms). Failure: A reading significantly outside this range indicates a defective coil.
• Fuel Injector Resistance (High-Impedance) — expected: 11 - 16 Ohms. Failure: A reading of 'OL' (open), near zero (shorted), or a value that differs by more than 1.0 Ohm from the other injectors. Consistency across all injectors is key.

Hidden / Shadow Codes Worth Checking

• Mode $06 Misfire Counter: This is not a DTC but a specific data parameter accessible with an advanced scan tool. It shows the raw count of misfire events per cylinder. A high count for cylinder 3 confirms the misfire is actively occurring, even if the Check Engine Light isn't flashing. (see via An advanced OBD-II scanner with Mode $06 data display capabilities.)

Scan Tool Commands That Help

• wiTECH (dealer tool) or equivalent high-level aftermarket scanner: Cylinder Cutout / Cylinder Kill Test — This bidirectional command is used to confirm a dead cylinder. The tool disables the fuel injector and/or ignition coil for cylinder 3. If the engine's idle quality does not change when cylinder 3 is 'cut out,' it confirms that cylinder was not contributing power, verifying the misfire location.

Wiring & Ground Locations

• Engine to Chassis Ground Strap — Typically a braided metal strap connecting the engine block or cylinder head to the vehicle's frame rail or firewall.. A loose, corroded, or missing main ground strap can cause unstable voltage and phantom electrical problems throughout the vehicle, including weak spark or erratic sensor readings that can lead to a misfire code. While not specific to cylinder 3, it's a foundational check for any electrical issue.

Real Owner Repair Stories

• YouTube channel 'Auto Repair Questions' (Dodge Magnum 3.5L V6 (similar engine family and cylinder layout)) — Cold misfire, shaking, P0303 code stored.
  ❌ Tried (didn't work) Initial diagnosis pointed to spark, coil, or wiring.
  ✅ What actually fixed it The porcelain insulator on the spark plug for cylinder 3 was cracked. Replacing the single spark plug resolved the misfire.
• YouTube channel 'Pancakes and Powerslides' (Dodge Challenger 3.6L V6) — Misfire on cylinder 3 (P0303).
  ❌ Tried (didn't work) The video is a direct repair, not a list of failed attempts.
  ✅ What actually fixed it The owner replaced the intake manifold gasket set to resolve the P0303 code.
• YouTube channel 'The Flat Rate Mechanic' (Dodge Challenger 5.7L Hemi) — Misfire on cylinders 1, 2, 3, and 4, stuttering, and occasional stalling.
  ❌ Tried (didn't work) Checked ignition coils., Checked and swapped fuel injectors.
  ✅ What actually fixed it A broken intake valve spring on one of the affected cylinders. The broken spring prevented the valve from closing completely, allowing exhaust pressure into the intake manifold and disrupting the air/fuel mixture for multiple cylinders on that bank.

"I Checked Everything" — The Actual Cause

• A common cause for an isolated cylinder misfire that isn't related to ignition or fuel components is a vacuum leak from the intake manifold gasket specific to that cylinder's runner. While a smoke test is the primary method to find such leaks, a gasket can fail intermittently based on engine temperature and expansion. If a smoke test on a cold engine is negative, the leak may only appear when the engine is hot. Visual inspection of the gasket after removing the intake manifold may be required to find a hardened, flattened, or torn section that was causing the leak.

OEM Part Supersession History

• 56029129AA, 56029129AB, 56029129AF, 68060346AA → 68238603AA — Part has been updated by the manufacturer over time for improved reliability or to consolidate inventory.
  Heads up: While the newer part may physically fit older models, it's crucial to use the correct part for the vehicle's specific production date, as internal electronics may differ. Using the wrong revision could lead to premature failure or improper performance.

Model Year Variations Within This Range

• 2014 vs. 2015+: The 2015 model year marked a major refresh, including an all-new interior, updated exterior styling, and a new 8-speed automatic transmission. For P0303, the most relevant change is the ignition coil part number, which was updated for vehicles built after April 17, 2015. Additionally, PCM software updates were common during this period; a 2017 update for 2015-2016 models inadvertently caused issues with Sport Mode, demonstrating that software logic can vary significantly year to year.