OBD-II Code P2305: Ignition Coil 'B' Secondary Circuit Malfunction

What Does P2305 Mean?

P2305 means your car's Powertrain Control Module (PCM) detected a fault in the secondary (high-voltage) circuit of ignition coil 'B', which fires cylinder #2 on most engines. The secondary circuit generates the thousands of volts required to push a spark across the spark plug gap. The PCM monitors the voltage and duration of every spark event. If the spark duration is too short, weak, or nonexistent, the computer logs code P2305.

Technical definition: The SAE/ISO definition is "Ignition Coil 'B' Secondary Circuit Malfunction". This indicates an abnormal voltage condition or open/short in the high-voltage circuit, which includes the coil's secondary winding, the coil boot/wire, and the spark plug. On Chrysler, Dodge, and Jeep vehicles, the definition is 'Ignition Coil 2 Secondary Circuit - Insufficient Ionization'. This means the PCM uses the spark plug as a sensor to measure combustion chamber ionization after firing, and the reading fell outside the expected range.

Can I Drive With P2305?

Yes, But With Caution. You can drive short distances, but a persistent misfire dumps raw fuel into the exhaust. This destroys your catalytic converter—a $1,500+ repair—in under 50 miles. If the check engine light flashes, pull over immediately to prevent catastrophic damage.

Common Causes

• Faulty Ignition Coil (Very Common) — A failed ignition coil causes the vast majority of P2305 codes. Constant heat and vibration break down the internal secondary windings or crack the plastic housing, creating a short or open circuit that prevents the coil from generating high voltage.
• Worn or Fouled Spark Plug (Common) — A spark plug with a worn electrode or heavy carbon/oil fouling requires significantly more voltage to fire. This increased electrical demand overworks the ignition coil, pushing the secondary circuit voltage outside the PCM's expected range.
• Damaged Spark Plug Wire or Coil Boot (Common) — The rubber boot on a coil-on-plug unit or the spark plug wire cracks and degrades from engine heat. This allows the high-voltage spark to arc directly to the engine block (ground) instead of reaching the spark plug tip.
• Wiring or Connector Issues (Less Common) — The electrical connector at the ignition coil suffers from loose pins, corrosion, or water intrusion (often from pressure washing the engine). The wiring harness can also chafe against metal components or suffer rodent damage, creating a short to ground.
• Failing Powertrain Control Module (PCM) (Uncommon) — The internal driver circuit that controls coil 'B' inside the PCM fails. This is a heavily documented factory defect on 2015-2016 Chrysler, Dodge, and Jeep 3.6L models, causing the PCM to set a P2305 code and repeatedly destroy new coils.
• Faulty Camshaft or Crankshaft Sensor (Very Rare) — An erratic signal from a timing sensor disrupts ignition timing. This causes the PCM to misinterpret the feedback from the ignition coil's secondary circuit, logging a false P2305 code.

Symptoms

• Flashing or Solid Check Engine Light — The PCM illuminates the Check Engine Light immediately. A flashing light indicates a severe, active misfire currently damaging the catalytic converter.
• Engine Misfire and Rough Idle — The engine shakes, stumbles, or vibrates noticeably, especially at idle or under light acceleration, because cylinder #2 is dead.
• Sluggish Acceleration — With one cylinder failing to contribute power, the vehicle hesitates and struggles to accelerate, particularly when climbing hills or merging.
• Raw Fuel Smell from Exhaust — Unburned fuel from the dead cylinder passes directly into the exhaust system, creating a strong gasoline odor at the tailpipe.
• Engine Stalling — The engine stalls when coming to a stop or idling in gear due to the severe RPM instability caused by the misfire.

Diagnostic Flowchart

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

Common Fixes & Costs

• Replace Ignition Coil 'B' — Parts: $30-$120, Labor: $50-$100, ~0.5 hr book time (DIY)
• Replace the Spark Plug(s) — Parts: $8-$30 (per plug), Labor: $100-$250 (full set), ~1.2 hr book time (DIY)
• Replace Spark Plug Wire or Coil Boot — Parts: $10-$40, Labor: $25-$50, ~0.3 hr book time (DIY)
• Repair Wiring or Replace Connector Pigtail — Parts: $15-$50, Labor: $100-$250, ~1.5 hr book time (Intermediate)
• Replace and Program Powertrain Control Module (PCM) — Parts: $300-$1,200, Labor: $200-$300, ~1.8 hr book time (Professional)

Used vs. New Parts: Buying Guide

When a used part is worth it: A used OEM coil from a low-mileage donor car is acceptable only for older, high-mileage vehicles where budget is the absolute priority.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the donor vehicle's mileage.
• Match the part number exactly; visual similarity guarantees nothing.
• Reject any coil with hairline cracks, white carbon tracking, or brittle rubber boots.

Decision logic:

• If Vehicle is newer or has under 100K miles → Buy a new OEM or premium aftermarket coil (Denso, NGK). The reliability is worth the $80.
• If Budget is extremely tight and the car is old → A $20 used OEM coil from a salvage yard is often more reliable than a $15 no-name Amazon coil.
• If The coil is buried under the intake manifold → Always buy new OEM. The 3 hours of labor required to replace a failed used part destroys any initial savings.

Warranty tradeoff: Used parts carry a 30-day warranty covering only the part. New aftermarket parts offer 1-year to lifetime warranties. New OEM parts offer 1-2 year warranties.

Worst-case if a used part fails: 200-500 if a used coil fails, requiring repeat labor and a new part.

What Happens If You Wait — Timeline

1. 0-1 week: Check Engine Light illuminates. A slight stumble occurs at idle. Performance loss is minimal. (MPG impact: 0-5%% · Added cost: $0)
2. 1 week - 2 months: Misfire becomes consistent. Acceleration is sluggish, and fuel economy drops. The Check Engine Light flashes under heavy load. (MPG impact: 5-15%% · Added cost: $50-150 in wasted fuel)
3. 2-4 months: Raw fuel superheats the catalytic converter, melting the internal honeycomb. A rotten egg smell emits from the exhaust. (MPG impact: 15-25%% · Added cost: $1200-2800 (catalytic converter replacement required))
4. 4+ months: Catalytic converter completely blocks the exhaust. The engine loses all power and stalls. Unburned fuel washes oil off cylinder walls, scoring the engine block. (MPG impact: 25-40%% · Added cost: $1500-3400 (catalyst, O2 sensors, and potential engine rebuild))

Cost of Not Fixing It

• Immediate (0-1 month): Noticeable 10-15% drop in fuel economy, rough idle, and poor acceleration. High risk of stalling in traffic. (Added cost: 50-150 in wasted fuel)
• Short-Term (1-6 months): Raw fuel from the dead cylinder superheats and melts the internal honeycomb substrate of the catalytic converter, causing permanent failure. (Added cost: 1200-2800 for catalytic converter replacement)
• Long-Term (6+ months): Prolonged misfiring fouls oxygen sensors and washes lubricating oil off the cylinder walls, leading to internal engine scoring and compression loss. (Added cost: 300-600 for O2 sensors, plus catastrophic engine damage)

Diagnosis Steps

1. Read the Codes and Freeze Frame Data
   Use an OBD-II scanner to confirm P2305. Look for companion codes like P0302 (Cylinder 2 Misfire), which confirms the affected cylinder. Review the freeze frame data to see the exact engine RPM, load, and temperature when the fault occurred.
   Tools: OBD-II Scanner (Beginner)
2. Swap the Ignition Coil (The Definitive Test)
   Swap the ignition coil from cylinder #2 (coil 'B') with the coil from cylinder #4. Clear the codes and drive the vehicle. If the check engine light returns and the code changes to P2308 (Coil 'D' on cylinder #4), you have proven the ignition coil is faulty.
   Tools: Basic socket set or screwdriver (Beginner)
3. Perform a Visual Inspection
   Inspect the wiring and connector for coil #2. Look for backed-out pins, green corrosion, or water inside the connector. Check the coil housing for hairline cracks or melted potting material. Inspect the rubber boot for white/grey carbon tracking lines, which indicate electrical arcing.
   Tools: Flashlight (Beginner)
4. Inspect the Spark Plug
   If swapping the coil didn't move the code, remove the spark plug from cylinder #2. Replace it immediately if you find a rounded center electrode, cracked porcelain, or heavy oil/carbon fouling.
   Tools: Spark plug socket, ratchet, extension (Intermediate)
5. Check for Power at the Coil Connector
   Disconnect the coil connector and turn the ignition to 'ON' (engine off). Use a multimeter to probe the power supply wire. You must see 12 volts. If voltage is missing, trace the wiring upstream to the fuse box or ASD relay.
   Tools: Digital Multimeter, vehicle-specific wiring diagram (Intermediate)
6. Test Ignition Coil Resistance
   With the coil removed, measure the primary resistance between the positive and negative terminals (typically 0.4 to 2.0 ohms). Measure the secondary resistance between the positive terminal and the spark plug boot (typically 6,000 to 15,000 ohms). An 'OL' reading means the coil is internally broken.
   Tools: Digital Multimeter (Advanced)
7. Test the ASD Relay Circuit (Chrysler/Dodge/Jeep Only)
   Chrysler coils receive power from the Auto Shutdown (ASD) relay. With the ignition on, probe the ASD Relay Output circuit at the coil connector with a 12V test light connected to ground. If it fails to illuminate brightly, the ASD relay or its wiring is faulty.
   Tools: 12-volt test light, wiring diagram (Advanced)
8. Analyze the Secondary Ignition Waveform
   Use an oscilloscope to view the coil's firing event. A healthy coil-on-plug system shows a 30-45 kV firing line and a spark burn time of at least 1.5 milliseconds. A P2305 fault typically reveals a burn time under 0.8 ms or no firing line at all.
   Tools: Automotive Oscilloscope with secondary probe (Advanced)
9. Test the PCM Driver Circuit
   If the coil, plug, and power supply are perfect, the PCM is suspect. Use a noid light or oscilloscope to check for a pulsing ground signal from the PCM to the coil while the engine cranks. No pulse confirms a dead PCM driver.
   Tools: Digital Multimeter, Noid Light, professional scan tool (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 190-210°F (Fully warmed up at normal operating temperature.)
• RPM: 2000-3000 RPM (Under load, during acceleration.)
• Engine Load: 40-70% (Moderate to heavy acceleration, like climbing a hill or merging onto a highway.)
• Vehicle Speed: 40-60 mph (Steady-state cruising or light acceleration at highway speeds.)

Related Codes

• P0302 — Cylinder 2 Misfire Detected. This is the most common companion code. P0302 identifies the symptom (misfire), while P2305 pinpoints the electrical cause.
• P0352 — Ignition Coil 'B' Primary Circuit Malfunction. Indicates a fault on the low-voltage side. Seeing P2305 and P0352 together guarantees a dead coil, a broken connector, or a fried PCM.
• P0300 — Random/Multiple Cylinder Misfire Detected. If present with P2305, the electrical fault is spreading, pointing to a failing PCM, a bad ASD relay, or a damaged wiring harness.
• P0202 — Injector Circuit / Open - Cylinder 2. Appears if the PCM intentionally shuts down the fuel injector to protect the catalytic converter from the persistent ignition fault.

Climate & Environmental Factors

• Cold Weather: Low temperatures increase electrical resistance within the coil's windings, exposing a weak coil that functions normally in warm weather.
• High Humidity / Moisture: Water intrusion from engine washing or heavy rain compromises the coil boot insulation, allowing the spark to arc to the engine block instead of firing the plug.
• High Altitude: Lower atmospheric pressure reduces the voltage required for a spark to jump a gap in open air. Weak coils will arc internally or to the block rather than firing inside the high-pressure combustion chamber.

How to Talk to a Mechanic About This Code

Say this: "My scanner shows a P2305 code for the ignition coil on cylinder 2, and the engine is misfiring. Please diagnose the coil, spark plug, and the wiring connector for cylinder 2."

This directs the mechanic to the exact problem area, preventing them from charging you for an open-ended, multi-hour diagnostic process.

Avoid saying:

• 'My check engine light is on, can you look at it?'
• 'Just fix whatever is making it shake.'
• 'I think it needs a tune-up.'

Questions to ask before authorizing the repair:

• Did you confirm the failure by swapping the coil to another cylinder?
• If the coil is good, did you verify the PCM is sending a ground pulse?
• Are you using an OEM replacement coil or an aftermarket brand?

Where to Take It: Dealer vs Independent vs Chain

• Dealer:
  Best for: Vehicles under powertrain warranty., Chrysler/Jeep models requiring the TSB PCM replacement., Complex PCM programming.
  Downsides: Highest labor rates., Will push for expensive OEM parts when premium aftermarket parts work fine. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit. P2305 is a standard ignition code that any ASE-certified independent shop can diagnose and repair efficiently.
  Best for: Out-of-warranty vehicles., Standard coil, plug, and wiring repairs., Owners seeking the best value.
  Downsides: May lack the dealer-level software required to program a new PCM. (Typical cost: +0% vs. baseline)
• Chain Shop: Avoid for diagnosis. They frequently misdiagnose wiring or PCM issues as simple coil failures, leading to wasted money.
  Best for: You already diagnosed a bad coil and just need someone to bolt a new one on.
  Downsides: High pressure to upsell unrelated fuel system cleanings., Incapable of diagnosing deep wiring or PCM faults. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the repair estimate exceeds 50% of the vehicle's private-party value, sell the car. For vehicles over 150,000 miles, lower this threshold to 40%.

• Car worth $4000, fix is $2200: Walk away. The repair cost is over 50% of the car's value.
• Car worth $12000, fix is $800: Fix it. The repair is well below the threshold and cheaper than a new car down payment.
• Car worth $2500, fix is $1500: Walk away. The repair cost is 60% of the vehicle's value.

What Scan Tool You Need for This Code

Minimum: An OBD-II scanner that reads codes, clears codes, and displays live data (specifically misfire counters).

A $20 code reader only gives you 'P2305'. It cannot show live misfire data, which is critical for verifying which cylinder is dead and confirming the repair worked.

Budget: BlueDriver Pro (~$99) — Connects via Bluetooth to your phone. Reads P2305, displays freeze frame data, and graphs live misfire counts to confirm the fault.

Mid-range: Foxwell NT510 Elite (~$180) — Offers bi-directional control to command components on and off, providing OE-level diagnostics for one specific car brand.

Professional: Autel MaxiCOM MK808 (~$499) — Provides full bi-directional control to test the PCM's ignition driver circuit directly, which is essential if you suspect a dead computer.

Rent vs buy: Auto parts stores read codes for free, but they cannot show live misfire data. If you plan to DIY this repair, buy the BlueDriver.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear P2305 and any companion misfire codes.
2. Perform a complete OBD-II drive cycle to force the PCM to run its self-tests.
3. Check the scanner for pending codes after the drive cycle completes.

Drive cycle (~30 minutes): Cold start the engine (off for 8+ hours). Idle for 3 minutes. Drive for 15 minutes in mixed city/highway conditions. Perform three 5-minute steady-speed cruises at 55 mph. Allow the vehicle to cool down.

Readiness monitors affected: Misfire Monitor, Catalyst Monitor, Oxygen (O2) Sensor Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery clears the code but resets all readiness monitors, guaranteeing an automatic emissions test failure.
• The code returns instantly upon startup if the electrical connector is not fully seated.
• Failing to keep the fuel tank between 15% and 85% prevents the EVAP monitor from running during the drive cycle.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An active P2305 is an automatic failure. After repair, all readiness monitors (except EVAP) must read 'Complete' before a retest, requiring up to 100 miles of driving.
• New York: NYS DMV inspections rely on the OBD-II scan. An illuminated Check Engine Light for P2305 results in immediate failure.
• Texas: In the 17 emissions-testing counties, an active P2305 code fails the OBD portion of the annual safety inspection.

Most Commonly Affected Vehicles

• Chrysler Town & Country / Pacifica (2015-2016) — TSB #18-069-16 REV A identifies a faulty PCM as the root cause for 3.6L V6 models built between July 27, 2015, and Sept 11, 2015. The PCM must be replaced.
• Dodge Grand Caravan / Ram 1500 (2004-2016) — The 2015-2016 Grand Caravan 3.6L suffers the same PCM defect as Chrysler models. Ram 1500s (especially 2004 Hemi models) frequently log this code due to wiring harness chafing.
• Jeep Wrangler (JK) / Grand Cherokee (2007-2017) — The 3.6L Pentastar V6 is prone to coil failures. Additionally, 2012+ models suffered cylinder head defects that fouled plugs, indirectly triggering P2305.
• Ford F-150 / Mustang (2004-2010) — On 4.6L and 5.4L Triton engines, this code often accompanies spark plug 'blowout,' where weak cylinder head threads fail, ejecting the plug and destroying the coil.
• Volkswagen Jetta / Passat / Rabbit (2005-2015) — The 2.5L 5-cylinder engine has a notoriously high ignition coil failure rate. Technicians strongly recommend replacing all five coils simultaneously.
• Chevrolet / GMC Silverado 1500 / Sierra 1500 (2014-2014) — GM bulletin PIP5147 addresses water intrusion into the coil connectors on 4.3L and 5.3L engines, requiring replacement and heavy application of dielectric grease.
• Hyundai / Kia Sonata / Optima (2011-2019) — On 2.4L GDI engines, P2305 points to a failed coil, but owners must inspect the spark plug for heavy oil fouling, which indicates deeper engine wear.
• Subaru Outback / Forester (2008-2018) — Accessing coils on the flat 'boxer' engine is difficult. Replacing coil #2 (driver's side front) requires removing the battery and battery tray.

Manufacturer-Specific Notes

• Chrysler / Dodge / Jeep: TSB #18-069-16 REV A is critical for 2015-2016 3.6L models. It states P2305 is caused by a defective PCM with poor environmental sealing. If your VIN falls within the build dates, replacing the coil is useless; you must replace the PCM.
• General Motors (Chevrolet / GMC): A service bulletin for 2014 V6/V8 trucks identifies water intrusion into the coil connectors as the primary cause. The fix requires replacing the coil and packing the new connector boot with dielectric grease.
• Ford: On 4.6L and 5.4L Triton V8s, P2305 accompanied by a loud ticking noise means a spark plug has blown out of the cylinder head, destroying the coil. This requires a $300-$500 thread repair insert (like a Time-Sert).
• Volkswagen: The 2.5L 5-cylinder engine burns through ignition coils rapidly. Because the coils degrade at the same rate, replacing just one usually results in another failing weeks later. Replace all five as a set.

Real Owner Stories

2015 Jeep Wrangler JKU with P2305 & P0302

Check Engine Light appeared. The owner replaced all spark plugs and coils, but the light returned within 48 hours.

What they tried:

1. Replaced all spark plugs.
2. Replaced all ignition coils.

Outcome: The issue was a loose wire in the harness connector for ignition coil #2. The pin had backed out, causing an intermittent connection. Pushing the pin back into the harness and securing the clip resolved the codes permanently.

Lesson: Never replace expensive components without meticulously inspecting the wiring connectors first. A backed-out pin perfectly mimics a dead coil.

2005 Dodge Grand Caravan 3.3L with P2305

Engine developed a severe misfire with code P2305 and no spark on cylinders 2 and 5.

What they tried:

1. Replaced ignition coil three times.
2. Replaced PCM twice.
3. Replaced spark plugs and wires.

Outcome: The problem persisted despite replacing every component. The owner eventually found a chafed wire deep in the main harness shorting to the engine block, destroying the new PCMs.

Lesson: If a new coil and PCM fail to fix a Chrysler misfire, stop throwing parts at it. You must perform a deep dive into the wiring harness to find the short circuit.

2007 Jeep Wrangler JKUR with P2305 & P0300

Vehicle misfired badly. The owner found the aftermarket ignition coil pack physically cracked and leaking potting material.

What they tried:

1. Replaced the cracked coil with a warranty replacement.
2. Cleared codes.

Outcome: The new coil failed immediately, and P2305 returned. A shop diagnosed a failed PCM driver circuit that was sending continuous voltage to the coil, literally melting it from the inside out. Replacing the PCM solved the issue.

Lesson: A physically melted ignition coil is a massive red flag. It indicates the PCM driver has failed closed. Installing a new coil without replacing the PCM will just melt the new coil.

How to Prevent This Code From Triggering

• Replace spark plugs at the manufacturer's recommended interval (Every 30,000 to 100,000 miles) — Worn spark plugs have wide gaps that require massive voltage to fire. This overworks the ignition coil, overheating and destroying its internal windings.
• Apply dielectric grease to the inside of the coil boot (Whenever replacing coils or spark plugs) — Dielectric grease seals out moisture and prevents the high-voltage spark from arcing through the rubber boot to the engine block.
• Avoid washing the engine bay with high-pressure water (Always) — High-pressure water bypasses weather seals on electrical connectors, causing immediate short circuits and long-term pin corrosion.

Frequently Asked Questions

What does the 'B' in P2305 mean?

The 'B' designates the second cylinder in the engine's firing order, which is almost always cylinder #2. Verify your vehicle's specific cylinder numbering and firing order in a repair manual.

What does 'Insufficient Ionization' mean on my Dodge/Jeep?

This is Chrysler's term for a weak or missing spark. The PCM uses the spark plug as a sensor to measure combustion chamber ions after firing. If the measurement fails, it sets P2305, usually due to a bad coil or plug.

I replaced the coil and plug, but P2305 came back. What's next?

Inspect the coil's electrical connector for corrosion or backed-out pins. Next, test the wiring between the coil and the PCM for proper voltage and ground. Finally, check for Technical Service Bulletins (TSBs), as a faulty PCM driver is a common hidden cause.

What is the ASD relay and could it cause P2305?

On Chrysler, Dodge, and Jeep vehicles, the Auto Shutdown (ASD) relay supplies power to the ignition coils. If this relay or its circuit fails, the coils lose power, triggering a P2305 code.

Can I replace the PCM myself?

Physically swapping the PCM is easy, but the new module requires specialized programming to sync with your vehicle's VIN and immobilizer keys. Without dealer-level software, the car will not start. Leave this repair to a professional shop.

What are common misdiagnosis mistakes for P2305?

The biggest mistake is replacing the coil without checking the electrical connector for corrosion, which instantly ruins the new part. Another error on Chrysler vehicles is ignoring a faulty PCM driver that repeatedly destroys replacement coils. Always test the circuit if a new coil fails quickly.

My Ford truck has a P2305 and a loud ticking noise. What is it?

On a Ford Triton V8, this combination means a spark plug has blown out of the cylinder head, destroying the coil. The ticking is combustion gas escaping past stripped threads. This requires a specialized thread repair insert like a Time-Sert.

Why is it so hard to change the coils on my Subaru?

Subaru's flat 'boxer' engine places the spark plugs and coils horizontally against the frame rails. Access is extremely tight, especially on the driver's side. You must remove the battery and battery tray just to reach the components.

Key Takeaways

• Code P2305 flags a high-voltage failure in ignition coil 'B', which corresponds to cylinder #2 on most engines.
• A dead ignition coil causes 80% of P2305 codes, making a $50-$150 DIY coil replacement the most likely fix.
• Swap the cylinder #2 ignition coil with cylinder #4; if the code changes to P2308, you have definitively proven the coil is bad.
• Chrysler, Dodge, and Jeep owners must check TSB #18-069-16; a known factory PCM defect causes this code and requires an $800-$1,200 module replacement.
• Pull over immediately if your Check Engine Light flashes; driving with an active misfire destroys a $1,500 catalytic converter in under 50 miles.