P0304 on 2010-2017 Volvo XC60: Cylinder 4 Misfire Causes and Fixes

What's Unique About the 2010-2017 Volvo XC60

While a misfire code can happen on any car, some 2015-2016 XC60 models with the 2.0L T5 'Drive-E' engine were known to have excessive oil consumption issues due to a piston ring design problem. This issue can lead directly to code P0304 by causing the spark plug in cylinder 4 to become fouled with oil, preventing a proper spark. For the 3.0L T6 engine, the inline-six configuration is generally robust, but misfires are still most commonly traced to ignition components. A burnt valve is also a known, albeit more serious, cause of misfires on the T6 engine, sometimes linked to prolonged use of lower octane fuel. For both engines, the diagnostic process is otherwise straightforward, typically starting with the ignition system.

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Solid or flashing Check Engine Light
• Reduced fuel economy
• Smell of unburned fuel from the exhaust
• Engine knocking or pinging sounds

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Ignition coils are a common wear item on modern engines and a very frequent cause of single-cylinder misfires on Volvos.
   How to confirm: Swap the ignition coil from cylinder 4 with another cylinder (e.g., cylinder 3). Clear the codes and drive the vehicle. If the code changes to P0303, the ignition coil is faulty. 🎬 See how to diagnose a P0303 misfire on this XC60.
   Typical fix: Replace the failed ignition coil. It is often recommended to replace all coils if they are the same age and mileage.
   Est. part cost: $50-$120
2. Worn or Fouled Spark Plug 🔴 High Probability On 2015-2016 2.0L T5 engines, known oil consumption issues can foul the spark plugs, causing a misfire. Otherwise, spark plugs are a standard maintenance item that wears out over time.
   How to confirm: Remove the spark plug from cylinder 4. Inspect it for wear (worn electrode), damage (cracked insulator), carbon buildup, or oil/fuel fouling. Compare its condition to a plug from another cylinder.
   Typical fix: Replace the spark plug. If plugs are old, replace the entire set. If the plug is oil-fouled on a T5, investigate the underlying oil consumption issue, which may require dealer intervention or piston ring replacement.
   Est. part cost: $10-$25 per plug
3. Faulty Fuel Injector 🟡 Medium Probability
   How to confirm: After ruling out spark issues, a mechanic can perform a fuel injector balance test. You can also listen to the injector with a mechanic's stethoscope to check for a consistent clicking sound. Swapping injectors between cylinders is a definitive test but is more labor-intensive than swapping coils.
   Typical fix: Replace the faulty fuel injector for cylinder 4. It's sometimes recommended to clean or replace all injectors if they are high mileage.
   Est. part cost: $70-$200

Rare But Worth Checking

• Low Engine Compression: This indicates a more serious mechanical issue, such as a worn piston ring, a burnt exhaust valve, or a damaged head gasket. This should be investigated with a compression test after ruling out spark and fuel issues. A user on Reddit with a T6 reported zero compression in a cylinder due to a burnt valve.
• Vacuum Leak: A vacuum leak from a cracked hose or a failed intake manifold gasket near cylinder 4 can lean out the air/fuel mixture and cause a misfire. On T6 engines, a failed PCV diaphragm built into the oil filter housing can also cause misfires.
• Clogged/Dirty Intake Valves: On direct-injection engines like the T5 and T6, carbon can build up on the back of the intake valves over time, restricting airflow to a specific cylinder and causing misfires, especially on cold starts.

Diagnosis Steps

1. Confirm the P0304 code using an OBD-II scanner. Note any other codes present.
2. Determine which engine you have (2.0L T5 4-cylinder or 3.0L T6 6-cylinder) and locate cylinder 4. On both engines, cylinders are numbered sequentially starting from the passenger side (timing belt side) of the engine bay.
3. Swap the ignition coil from cylinder 4 with the coil from cylinder 3.
4. Clear the codes and start the engine. Let it run until the check engine light reappears or check for pending codes.
5. If the code is now P0303, you have a bad ignition coil. Replace it.
6. If the code remains P0304, turn off the engine and remove the spark plug from cylinder 4. Inspect it for wear, damage, or oil/fuel fouling.
7. If the spark plug is worn or fouled, replace it (and likely the others if they are old). If it's heavily oil-fouled on a 2015-2016 T5, be aware of the potential for a larger oil consumption problem related to piston rings.
8. If both the coil and plug are good, the issue is likely fuel-related or mechanical. Inspect the injector wiring for any visible damage. Listen for a steady clicking from the injector with a stethoscope.
9. For a more definitive test, swap the fuel injector from cylinder 4 with cylinder 3. This is more involved but will confirm a faulty injector if the code moves to P0303.
10. If spark and fuel systems seem okay, perform a compression test on cylinder 4 to check for mechanical engine problems like bad rings or valves. A YouTube video on a 2015 XC60 with P0304 demonstrated using a pressure transducer for in-depth analysis. 🎬 Watch: A professional diagnostic walkthrough of a 2015 XC60 P0304. A Reddit user with a T6 ultimately found a burnt valve was the cause after replacing ignition and fuel parts.

Parts You'll Likely Need

• Ignition Coil (OEM #30684245 (for 3.0L T6), 31312514 (for 2.0L T5)) — Ignition coils are a common failure item that directly causes a single-cylinder misfire.
  Trusted brands: Bosch (OEM supplier), Delphi, NGK, Bremi
  OEM price range: $80-$150
  Aftermarket price range: $40-$90
• Spark Plug — Spark plugs are a routine maintenance item. A worn, cracked, or fouled plug cannot create the spark needed for combustion.
  Trusted brands: Volvo (OEM), NGK, Bosch
  OEM price range: $20-$30
  Aftermarket price range: $10-$20

Related Codes That Often Appear With This One

• P0300 — If the misfire becomes more widespread or intermittent across cylinders, a P0300 (Random/Multiple Cylinder Misfire) may appear.
• P0420 — A persistent misfire allows unburnt fuel into the exhaust, which can overheat and damage the catalytic converter, triggering a code for low catalyst efficiency.
• P0204 — This code indicates an electrical fault in the cylinder 4 injector circuit (e.g., open or short) and points more directly to a wiring or injector problem rather than a spark issue.

Technical Service Bulletins (TSBs) & Recalls

• Volvo Technical Journal (TJ) 31418: Addresses excessive oil consumption on 2015-2016 2.0L (Drive-E) engines, a root cause for oil-fouled spark plugs and misfires like P0304. The fix often involves replacing pistons and piston rings.

Platform-Specific Known Issues

• Some 2015-2016 models with the 2.0L T5 four-cylinder 'Drive-E' engine were susceptible to high oil consumption due to faulty piston ring design. This can cause spark plugs to foul with oil, leading to misfire codes like P0304. Volvo addressed this with Technical Journal TJ 31418 and an extended warranty for some vehicles. Owners report needing to add oil weekly and eventual engine failure in severe cases.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance — expected: Typically 10-18 Ω (for high-impedance injectors common on these models). Failure: A reading significantly outside this range, or an open/infinite resistance, indicates a failed injector coil.
• Fuel Injector Voltage (Key On, Engine Off) — expected: Approximately 12V (Battery Voltage) at the power supply pin of the injector connector.. Failure: No voltage suggests a problem with the wiring, fuse, or relay supplying power to the injectors.
• Live Misfire Count (Using Volvo VIDA) — expected: The counter for cylinder 4 should be zero or near-zero on a healthy engine.. Failure: The misfire counter for cylinder 4 will increment rapidly during a misfire event, confirming the fault is actively occurring.

Scan Tool Commands That Help

• Volvo VIDA: Live Data Monitoring / Misfire Counters — Use this function to watch individual cylinder misfire counts in real-time. This is invaluable for diagnosing intermittent misfires that don't immediately set a hard code, as you can see which cylinder is stumbling even for a moment.
• Volvo VIDA: Fault Trace - Data View — After reading a DTC, VIDA's 'Data view' can show frozen data values from the moment the fault was detected, status bits (e.g., if the fault is confirmed or temporary), and fault counters. This helps determine if the misfire happened under specific conditions (load, temp) and how frequently it occurs.

Wiring & Ground Locations

• Engine Ground Straps — Key grounds are located on the strut towers in the engine bay (both passenger and driver side). There are also grounds on the top of the engine itself.. A corroded or loose engine ground can cause erratic behavior in the ignition system, leading to weak spark and misfires. While not specific to cylinder 4, checking main grounds is a crucial step if ignition problems seem widespread or intermittent.
• Ignition Coil Connector — Directly on top of each ignition coil, under the plastic engine cover.. The plastic locking tabs on these connectors can become brittle with age and break, leading to a poor connection. A loose connection at the cylinder 4 coil can cause an ignition circuit fault (like P0354) or a misfire (P0304).
• ECM (Engine Control Module) — Located in the left rear of the engine compartment (driver's side, near the firewall).. The ECM provides the ground pulse to fire the ignition coil and fuel injector. While rare, a faulty driver circuit in the ECM for cylinder 4 could be the cause, but this should only be considered after all other wiring, coil, plug, and injector issues are ruled out.

Real Owner Repair Stories

• Reddit user in r/MechanicAdvice (2013 Volvo XC60 T6, 150,000 miles) — Sudden, pronounced misfire on cylinder 6 (P0306).
  ❌ Tried (didn't work) New spark plugs and ignition coils, Swapping coils and plugs between cylinders, New fuel injector (aftermarket), Replacing the entire cylinder head with a low-mileage used unit, Replacing the fuel injector again with a genuine Volvo part
  ✅ What actually fixed it The issue was never resolved by the original poster in the thread, who had replaced nearly every component related to the cylinder. The final suspicion fell on a wiring harness issue or a faulty ECM driver, highlighting a case where common fixes fail.
• Reddit user in r/Volvo (2015.5 Volvo XC60 T6, 152,000 miles) — Engine shuddering, Check Engine Light with codes for cylinder 2 and 4 misfire.
  ❌ Tried (didn't work) Replacing spark plugs, Testing all ignition coils
  ✅ What actually fixed it A compression test revealed 0 lbs of compression in cylinder 4. A Volvo mechanic confirmed a burnt valve, requiring engine replacement. The owner opted to get a new car rather than repair.

When the Usual Fixes Don't Work

• In one documented case for a similar P-platform Volvo, a persistent misfire on a 2013 T6 engine was not resolved by replacing the coil, plug, injector, or even the entire cylinder head. This suggests that in very rare instances, the root cause can be a fault in the engine wiring harness or the Engine Control Module (ECM) itself, which are significantly more difficult and expensive to diagnose and repair than the common components.

OEM Part Supersession History

• 31358940 → 31312514 — Part revision or manufacturer change for the ignition coil used on the 2.0L T5 'Drive-E' engine.
• N/A → 30684245 — This is the established part number for the ignition coil on the 3.0L T6 'SI6' engine. It also cross-references to Land Rover part LR002954.

Model Year Variations Within This Range

• 2010-2014 (approx.): Primarily used the 3.0L T6 and 3.2L inline-six engines. Misfire diagnosis on these engines is very traditional, focusing on coils, plugs, injectors, and potential mechanical issues like burnt valves.
• 2014-2017: The 2014 model year marked a major facelift and the introduction of the 2.0L T5 'Drive-E' four-cylinder engine family, which gradually replaced the six-cylinders. These direct-injection engines are known for the specific oil consumption issue (2015-2016) leading to fouled plugs and are also susceptible to intake valve carbon buildup causing misfires.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Excessive Oil Consumption (2.0L T5) 🔴 High — Common on 2015-2016 models with the 2.0L 'Drive-E' engine. Can start as early as 60k miles. (Ref: Volvo TJ 31418)
• Haldex AWD System Failure 🟠 Medium — The pump can fail due to a clogged filter, often around 40k-60k miles. The DEM (Differential Electronic Module) can also fail from water intrusion on older, high-mileage vehicles. (Ref: P1889 is a common fault code for pump failure.)
• Transmission Shift Quality Issues (TF-80SC) 🟠 Medium — Can develop harsh shifting or hesitation, particularly in early (2009-2014) models. Often related to old fluid or requires a software update.
• Infotainment System Glitches 🟡 Low — Owners report issues with screens freezing or going blank, and general software bugs across multiple model years. (Ref: Often addressed by dealer software updates.)
• Accessory Drive Belt/Tensioner Noise 🟡 Low — The belt tensioner and idler pulley on the 3.0L/3.2L SI6 engines can wear out, causing chirping or rattling noises.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, buying used parts is generally not recommended for the key components. The only exception might be a major mechanical component like a complete cylinder head or engine block from a reputable salvage yard with a warranty, but only as a last resort for a major mechanical failure like a burnt valve.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a major component like a cylinder head, verify the donor vehicle's mileage.
• Inspect for any visible signs of overheating (warping, discoloration).
• Ensure the salvage yard offers a warranty against cracking or other defects.

OEM-only on this vehicle (don't cheap out):

• Fuel Injectors: While aftermarket injectors exist, OEM (Bosch is the supplier) or genuine Volvo injectors are strongly recommended to ensure correct flow rates and spray patterns. Poor quality injectors can cause persistent performance issues.
• PCV Oil Trap/Housing: For T6 engines, the integrated PCV system is complex. Using a genuine Volvo or OEM part is critical to avoid immediate failure or new vacuum leaks.

Aftermarket brands forum-validated for this vehicle:

• Ignition Coils: Bosch (often the OEM supplier), NGK, Delphi, Bremi.
• Spark Plugs: NGK, Bosch (ensure correct heat range and gap for your specific engine).

Brands owners have reported issues with on this vehicle:

• Unbranded, 'white-box' ignition coils and fuel injectors from online marketplaces. These often have high failure rates and may not meet the specific resistance or flow requirements of the engine, leading to continued misfires or new fault codes.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0303 — This code appears during the diagnostic process if the faulty ignition coil or fuel injector is swapped from cylinder 4 to cylinder 3 to confirm the failure.
• P0420 — A catalyst efficiency code that often appears alongside P0304 because the engine misfire can damage or overwhelm the catalytic converter.
• P1889 — A common fault code for the Haldex AWD pump failure, which is a known issue on this vehicle platform, though unrelated to engine misfires.

Frequently Asked Questions