P2304 on 2021-2024 Ford Bronco: Ignition Coil 'B' Circuit Fault Causes and Fixes

What's Unique About the 2021-2024 Ford BRONCO

The 2021-2024 Ford Bronco with the 2.3L EcoBoost engine is subject to specific Technical Service Bulletins (TSBs) that are critical for diagnosing P2304. Ford has identified that the PCM software can incorrectly map the Diagnostic Trouble Code (DTC) to the wrong cylinder, leading to misdiagnosis. This means a code for one cylinder might actually indicate a fault with another, or it could be a pure software glitch. Therefore, checking for a PCM software update is the most important first step, before any physical parts are replaced. This issue is also seen on the platform-mate Ford Ranger.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on, may be solid or flashing
• Rough or uneven idle
• Engine hesitation or stumbling during acceleration.
• Reduced engine power.
• Possible engine stalling under load.
• Audible misfire or 'popping' from the exhaust

Most Likely Causes

1. Powertrain Control Module (PCM) Software Error 🔴 High Probability Ford has issued TSB 24-2406 and SSM 52342 specifically for this issue on 2021-2024 Broncos with the 2.3L engine, indicating a known problem with incorrect cylinder-to-DTC mapping.
   How to confirm: A Ford dealer or a qualified shop with access to Ford's diagnostic tools (FDRS) can check if the vehicle's PCM software is outdated and if TSB 24-2406 applies. This is the definitive first step.
   Typical fix: Reprogramming the PCM to the latest software level. This is a dealer or professional-level repair. Note that after a PCM update, the transmission's adaptive learning may be reset, which can result in firmer-than-normal shifts for a few days.
   Est. part cost: $0 (if under warranty)
2. Faulty Ignition Coil 🟡 Medium Probability Coil-on-plug systems are common failure points due to high heat and vibration in the engine bay. The code directly points to a fault in the coil's circuit.
   How to confirm: After confirming the PCM software is up-to-date, swap the ignition coil from the suspect cylinder (typically #2) with one from another cylinder (e.g., #1). Clear the codes and drive. If the code changes to P2301 (for coil 'A'), the coil is bad.
   Typical fix: Replace the failed ignition coil. This is a straightforward DIY task requiring an 8mm socket.
   Est. part cost: $40-$80
3. Damaged Wiring or Connector ⚪ Low Probability Engine vibrations and heat can cause wiring to chafe or connectors to become loose or corroded. On some 2.3L EcoBoost platforms, wires inside the protective loom leading to the coil connector have been found broken. Corrosion at main body harness connectors, such as the one at the left-hand inner fender, has also been noted by owners.
   How to confirm: Visually inspect the wiring harness and connector for the ignition coil. Pull back the plastic loom to check for broken or chafed wires. Look for any signs of melting, corrosion, or pushed-out pins. Perform a wiggle test on the harness 🎬 Watch: Helpful tips for diagnosing a cylinder misfire. with the engine running to see if it induces a misfire.
   Typical fix: Repair the damaged section of the wiring harness or replace the connector pigtail. This may involve soldering and heat-shrinking the broken wire.
   Est. part cost: $10-$50
4. Worn or Fouled Spark Plug ⚪ Low Probability While a common maintenance item, a bad spark plug can increase resistance in the secondary ignition circuit, potentially triggering this code. Turbocharged engines are harder on plugs than naturally-aspirated ones. The correct spark plug gap is 0.028 - 0.031 inches (0.7 - 0.8 mm).
   How to confirm: If swapping the coil doesn't move the code, perform the same swap test with the spark plugs. Visually inspect the plug for wear, oil/carbon fouling, or cracks in the ceramic insulator.
   Typical fix: Replace the spark plug. It's recommended to replace all plugs at the same time for even performance. The OEM plugs are Iridium and should not be substituted with cheaper copper plugs.
   Est. part cost: $15-$30 per plug

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): This is rare. Before condemning the PCM, all other possibilities, especially the software update and wiring, must be exhaustively ruled out. A failed ignition driver inside the PCM is a last-resort diagnosis.

Diagnosis Steps

1. Check for Technical Service Bulletins (TSBs). This is the most critical first step. Contact a Ford dealer with your VIN or use a professional database to see if TSB 24-2406 or SSM 52342 apply to your vehicle. If so, a PCM reprogram is the first and most likely fix.
2. If no TSBs apply or the software is current, identify the cylinder associated with 'Ignition Coil B'. On the 2.3L I4, this is typically cylinder #2 (second from the front).
3. Perform an 'Ignition Coil Swap Test'. Turn off the engine. Swap the ignition coil from cylinder #2 with the coil from cylinder #1. Clear the codes with a scanner.
4. Drive the vehicle until the Check Engine Light returns. If the code has changed to P2301 (Ignition Coil 'A' Secondary Circuit), the ignition coil you moved is faulty and must be replaced.
5. If the code remains P2304, the coil is likely good. Repeat the swap test with the spark plugs between cylinders #2 and #1.
6. If the code does not follow either the coil or the plug, carefully inspect the wiring harness and connector for coil #2. Peel back any protective tape or loom and check for broken, brittle, or chafed wires. Check for corrosion in the main harness connectors near the inner fender.
7. If all parts and wiring appear to be in good condition, the issue may be an internal fault in the PCM, but this is very uncommon and should be the last consideration.

Parts You'll Likely Need

• Ignition Coil (OEM #P2GZ-12029-A) — This is the most common hardware failure for this code after a PCM software issue has been ruled out.
  Trusted brands: Motorcraft, NGK, Denso
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Spark Plug (OEM #SP-578 (CYFS-12Y-RT3)) — A worn or fouled spark plug can cause or contribute to ignition coil circuit faults. They are often replaced along with a failed coil. It is widely reported that NGK manufactures the OEM plug for Ford.
  Trusted brands: Motorcraft, NGK
  OEM price range: $20-$30
  Aftermarket price range: $15-$25

Related Codes That Often Appear With This One

• P0302 — P0302 is a generic code for 'Cylinder 2 Misfire Detected'. P2304 is a more specific Ford code pointing to the cause of that misfire being the ignition coil 'B' (cylinder 2) secondary circuit.
• P0352 — This code indicates a fault in the primary circuit of the same ignition coil. Seeing P0352 and P2304 together strongly points 🎬 See how to diagnose Ford ignition coil circuit codes. to an issue with the coil itself or its wiring/connector.
• P2303, P2306, P2309, etc. — These are all secondary ignition coil circuit codes for other cylinders. TSB 24-2406 lists all these codes as part of the same potential PCM software issue.

Technical Service Bulletins (TSBs) & Recalls

• TSB 24-2406: Notes that 2021-2024 Broncos with the 2.3L EcoBoost may exhibit an illuminated MIL with various ignition system DTCs, including P2304, due to incorrect cylinder to DTC mapping within the PCM.
• SSM 52342: A special service message that also highlights the incorrect cylinder to DTC mapping issue in the PCM for the 2.3L EcoBoost, leading to codes like P2304.

Platform-Specific Known Issues

• TSB 24-2406 / SSM 52342: A significant number of 2021-2024 Broncos with the 2.3L EcoBoost engine may set code P2304 (and other ignition codes) due to a PCM software error that incorrectly maps the fault to the cylinder. The official fix is to reprogram the PCM with the latest software.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.5 Ω to 2.0 Ω. Failure: A reading outside this range indicates a faulty coil.
• Ignition Coil Secondary Resistance — expected: 6,000 Ω to 10,000 Ω (6 kΩ - 10 kΩ). Failure: A reading significantly outside this range suggests a faulty coil.
• Ignition Coil Control (Driver) Pin Voltage — expected: Pulses between ~0-1V (driver ON) and battery voltage (~12V) (driver OFF) while engine is running.. Failure: Voltage staying high (> 2.0V) when it should be low indicates a circuit problem or faulty PCM driver.
• Spark Plug Gap — expected: 0.028 - 0.031 inches (0.7mm - 0.8mm). Failure: An incorrect gap can lead to inefficient spark and misfires.

Hidden / Shadow Codes Worth Checking

• Mode $06, TID $53: This is not a traditional DTC, but a monitor ID within the PCM's onboard diagnostic data. It tracks the raw misfire count for each cylinder, which can reveal intermittent misfires on a specific cylinder before they are frequent enough to set a P030x trouble code. (see via Requires a professional scan tool like Ford's IDS or an advanced DIY tool like FORScan that can access Mode $06 data.)

Scan Tool Commands That Help

• Ford IDS, FORScan, or advanced professional scanner (e.g., Snap-on): Power Balance Test — This test is critical for this specific vehicle and code. SSM 52342 explicitly recommends using it *before* physical diagnosis because the PCM may report a code for the wrong cylinder. The test disables fuel to each cylinder one by one and graphs the RPM drop. The cylinder that shows little or no RPM drop is the one with the actual misfire, regardless of what the P-code indicates.

Wiring & Ground Locations

• G110 / G120 — These are specific ground point designators. Their exact physical location can be found in the Ford service manual under 'Component Location Views'. A forum user mentioned these as key grounds to inspect when troubleshooting multiple electrical DTCs.. The ignition system is highly sensitive to poor grounds. A compromised ground can cause erratic voltage and trigger ignition circuit fault codes.
• Kick Panel Grounds — There are ground points located near the kick-panel speakers on the driver and passenger sides.. These are relatively accessible chassis ground points that can be checked for corrosion or looseness, which could affect various electronic systems, including the PCM and its sensor inputs.