P0355 on 2021-2024 Ford Bronco: Ignition Coil 'E' Causes and Fixes

What's Unique About the 2021-2024 Ford BRONCO

The 2021-2024 Bronco has a very specific and well-documented issue related to this code family. Ford issued Technical Service Bulletins (TSBs) because the PCM software can have 'incorrect cylinder to DTC mapping'. This affects the 2.3L EcoBoost, 2.7L EcoBoost, and 3.0L EcoBoost (Raptor) engines. This means that while your scanner reads P0355 (for cylinder 5), the actual faulty coil could be on a completely different cylinder. This issue can even cause a P0355 code to appear on the 2.3L 4-cylinder engine, which doesn't have a fifth cylinder. This makes blindly replacing the coil for cylinder 5 a common and costly mistake on this specific vehicle.

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 is on
• Rough or shaking idle
• Engine stumbling or hesitating on acceleration
• Noticeable loss of power
• Engine running rougher than usual
• A flashing Check Engine Light, indicating a severe misfire
• Sputtering or popping sounds from the exhaust

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Ignition coils are common wear items. Ford has issued TSBs covering a range of ignition system DTCs on these engines, indicating a known pattern of issues. Forum discussions also point to coil packs being a frequent failure point on EcoBoost engines.
   How to confirm: After identifying the correct cylinder with a power balance test, swap the suspect ignition coil with one from another cylinder. Clear the codes. If the code returns for the new cylinder (e.g., P0352 if you moved it to cylinder 2), the coil is bad.
   Typical fix: Replace the failed ignition coil. It is often recommended to replace the corresponding spark plug at the same time.
   Est. part cost: $40-$90
2. PCM Software Glitch (Incorrect Cylinder Mapping) 🔴 High Probability This is a documented issue acknowledged by Ford in TSB 24-2406 and SSM 52342 for 2021-2024 Broncos with 2.3L and 3.0L engines. The bulletins explicitly state the PCM may have 'incorrect cylinder to DTC mapping.'
   How to confirm: The code (e.g., P0355) does not match the failing cylinder found during a power balance test. For example, the code is P0355 but the power balance test shows cylinder 2 is misfiring.
   Typical fix: The PCM must be reprogrammed by a dealer or qualified shop with the latest Ford software to correct the mapping. This is done after replacing the actual failed hardware component (like a coil or plug).
   Est. part cost: $0 (labor for reprogramming will apply, typically 1-1.5 hours)
3. Damaged Wiring or Loose Connector 🟡 Medium Probability Engine vibrations and heat can cause wiring to become brittle or connectors to loosen over time. A visual inspection of the harness is a key diagnostic step.
   How to confirm: Visually inspect the wiring harness and connector for the failing ignition coil. Check for chafed or broken wires, and ensure the connector is clean, free of corrosion, and securely latched. Use a multimeter to check for proper power, ground, and signal at the connector pigtail.
   Typical fix: Repair the damaged section of the wiring harness or replace the connector pigtail. Motorcraft offers connector kits like WPT-1492 for this purpose.
   Est. part cost: $15-$50
4. Worn or Faulty Spark Plug ⚪ Low Probability → Shop Spark Plug While less likely to cause a circuit code than a misfire code (P030x), a spark plug with an excessive gap or internal short can over-stress the ignition coil, leading to a circuit fault. Owners on forums have noted that bad plugs can lead to coil failure.
   How to confirm: Remove the spark plug from the affected cylinder and inspect it for wear, damage, or carbon/oil fouling. Check the gap against manufacturer specifications.
   Typical fix: Replace the spark plug. It's best practice to replace all spark plugs as a set 🎬 See this walkthrough on changing Bronco 2.7L spark plugs if they are near the end of their service life.
   Est. part cost: $10-$25 per plug

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is the least likely cause. The internal driver circuit for the ignition coil can fail, but all other possibilities should be exhausted before condemning the PCM.
• Water Intrusion in Spark Plug Well: → Shop Spark Plug On the related 2.3L EcoBoost in the Ford Ranger, water leaking from the cowl area into the spark plug wells is a known issue that shorts out coils and plugs, 🎬 Watch: Diagnosing common Ford EcoBoost cold start misfires covered by TSB 23-2011. While not specifically documented for the Bronco, it's a plausible cause given the shared engine architecture.

Diagnosis Steps

1. Connect an OBD-II scanner to confirm the P0355 code and check for any other related codes.
2. CRITICAL: Due to Ford TSB 24-2406 and SSM 52342, do not assume cylinder 5 is the problem. The code is likely pointing to the wrong cylinder.
3. Have a professional technician perform a 'power balance test' using a Ford-specific diagnostic tool (FDRS). This test will identify which cylinder is actually losing power, regardless of the P0355 code.
🎬 Watch: How to perform a cylinder power balance test
4. Per SSM 52342, if the power balance test shows two cylinders dropping out, the PCM is shutting off fuel to the cylinder it *thinks* is bad. The actual faulty component is on the *other* cylinder that is dropping out. If only one cylinder drops out, that is the one to diagnose.
5. Once the correct failing cylinder is identified, locate its ignition coil.
6. Visually inspect the coil, its electrical connector, and the wiring harness for any signs of damage, corrosion, or loose connections.
7. If no visual issues are found, swap the ignition coil from the failing cylinder with a coil from a known good cylinder.
8. Clear all DTCs and start the engine. Let it run and then re-scan for codes.
9. If the code has moved to the new cylinder (e.g., P0352 after swapping with cylinder 2), the ignition coil is faulty and must be replaced.
10. If the original code (P0355) or a code for the original failing cylinder returns, the problem is likely in the wiring or the PCM driver for that circuit. Test the wiring for power, ground, and signal.
11. After replacing the faulty hardware (coil, plug, or wiring), the PCM should be reprogrammed with the latest software by a Ford dealer or qualified shop to correct the underlying mapping error and prevent future misdiagnosis.

Parts You'll Likely Need

• Ignition Coil (OEM #2.3L I4: Motorcraft DG-576 (also JX6Z-12029-A/B). 2.7L V6 / 3.0L V6: Motorcraft DG-588.) — This is the most common component to fail, causing the P0355 circuit code.
  Trusted brands: Motorcraft, NGK, Denso, Delphi
  OEM price range: $70-$135
  Aftermarket price range: $40-$90
• Spark Plug (OEM #Motorcraft SP-594 (supersedes SP-578). Part number CYFS-12Y-RT3 also applies. Fits 2.3L, 2.7L, and 3.0L engines.) — Often replaced as a preventative measure along with the ignition coil, as a worn plug can stress the new coil.
  Trusted brands: Motorcraft, NGK, Bosch
  OEM price range: $15-$30
  Aftermarket price range: $10-$20
• Ignition Coil Connector (OEM #Motorcraft WPT-1492) — If the connector or pigtail wiring is found to be damaged, it will need to be replaced to ensure a solid connection to the new coil.
  Trusted brands: Motorcraft, Dorman, Standard Motor Products
  OEM price range: $45-$55
  Aftermarket price range: $15-$35

Related Codes That Often Appear With This One

• P0305 — P0305 means 'Cylinder 5 Misfire Detected'. Since P0355 indicates a fault that prevents the coil from firing the spark plug, a misfire is the direct result. P0355 is the cause, and P0305 is the effect.
• P0351, P0352, P0353, P0354, P0356 — Due to the PCM mapping issue, the actual fault might be on cylinders 1, 2, 3, 4, or 6, but the PCM incorrectly logs it as a P0355.
• P2303, P2306, P2309, P2312, etc. — These are codes for 'Ignition Coil Primary Control Circuit Low/High'. They are also listed in the same TSBs as P035x codes and are symptoms of the same incorrect cylinder mapping issue.

Technical Service Bulletins (TSBs) & Recalls

• TSB 24-2406: Notes that 2021-2024 Broncos with 2.3L/3.0L engines may show various ignition DTCs, including P0355, due to incorrect cylinder-to-DTC mapping in the PCM, and advises reprogramming the PCM.
• SSM 52342: Explains that when ignition DTCs like P0355 appear, they may be for the incorrect cylinder. It instructs technicians to use a power balance test to find the actual faulty cylinder. It further clarifies that if two cylinders drop out during the test, the PCM is cutting fuel to the cylinder associated with the DTC, and the *other* cylinder is the one with the actual ignition fault.

Platform-Specific Known Issues

• Ford has issued TSB 24-2406 and SSM 52342 for 2021-2024 Broncos with 2.3L, 2.7L, and 3.0L EcoBoost engines. These bulletins warn that the PCM may have 'incorrect cylinder to DTC mapping,' causing it to log a fault for the wrong cylinder. The official corrective action involves identifying the true failing cylinder with a power balance test, repairing the underlying ignition system component, and then reprogramming the PCM to the latest software level to prevent the issue from recurring.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: Approximately 0.4 to 2.0 ohms (general Ford spec). Some sources cite 0.55 ohms for similar Motorcraft coils.. Failure: A reading of infinity (OL) indicates an open circuit. A reading of zero indicates a short. Significant deviation from the expected range suggests a faulty coil.
• Ignition Coil Secondary Resistance — expected: Approximately 6,000 to 15,000 ohms (6k-15k Ω). Some sources cite 5,500 ohms for similar Motorcraft coils.. Failure: A reading of infinity (OL) indicates an open secondary winding. A reading far outside the specified range indicates an internal coil problem.
• Spark Plug Gap — expected: 0.027 - 0.031 inches. Failure: A gap that is too wide or too narrow can cause inefficient spark and lead to misfires.

Scan Tool Commands That Help

• Ford Diagnostic and Repair System (FDRS): Power Balance Test — This is the primary diagnostic step required by Ford's TSBs for this issue. It graphically displays the power contribution of each cylinder, allowing a technician to identify the actual misfiring cylinder, even when the DTC (like P0355) points to the wrong one.
• Ford Diagnostic and Repair System (FDRS): PCM Reprogramming — After the physical repair (e.g., replacing a bad coil) is complete, the PCM must be updated to the latest software calibration to correct the underlying 'incorrect cylinder to DTC mapping' glitch and prevent future misdiagnosis.
• High-end Bi-directional Scanners: Injector Buzz Test / Coil Active Test — Can be used to command individual coils to fire or injectors to click. While the Power Balance test is more definitive for this specific Ford issue, an active test can help confirm if the coil driver circuit in the PCM is responding to commands.

Wiring & Ground Locations

• G104 — On the 2.7L engine, this ground is typically located on the front of the engine block or cylinder head area. Specific diagrams should be consulted for exact placement.. This is a primary engine-to-chassis ground. A loose or corroded G104 can cause unstable voltage and erratic behavior in multiple electronic systems, including the ignition system, potentially leading to intermittent circuit codes like P0355.
• Ignition Coil Connector (WPT-1492) — Directly on top of each ignition coil, pushed onto the 2-pin or 3-pin connector of the coil body.. This connector is the direct interface for the coil's primary circuit. The P0355 code specifically refers to a fault in this circuit. The connector pins, wiring pigtail, and locking tab are common failure points due to engine heat and vibration.
• Cylinder #5 Location (2.7L/3.0L V6) — On the transverse mounted 2.7L/3.0L EcoBoost V6, cylinder #5 is the middle cylinder on the firewall side (Bank 2).. While the code may be misleading due to the TSB, a technician must still know the physical location of cylinder 5 to begin diagnosis, even if it's just to swap the coil to another cylinder.

Real Owner Repair Stories

• Bronco6G Forum User (2021 Bronco Wildtrak (2.7L V6), 300 miles) — Check engine light came on, malfunction indicator lamp warning, car started to vibrate while driving on the interstate.
  ❌ Tried (didn't work) The user immediately took the vehicle to the dealer.
  ✅ What actually fixed it The dealer diagnosed and replaced a single defective ignition coil. They had to test the six cylinders to identify the bad one.
• Bronco6G Forum User (2022 Bronco Badlands (2.7L V6), 23,000 miles) — Rough idle, extended crank (no codes initially). Later, a flashing check engine light with misfires on cylinder 1 and multiple random misfires.
  ❌ Tried (didn't work) First dealership replaced the vapor management valve, which did not fix the issue.
  ✅ What actually fixed it A different dealership diagnosed the issue as faulty fuel injectors and replaced the injectors for cylinders #1 and #3.

OEM Part Supersession History

• DG-583, PB5Z-12029-A → Motorcraft DG-588 — Standard part revision and consolidation for multiple vehicle applications.

Model Year Variations Within This Range

• 2022: For the 2022 model year, Ford introduced a newly available manual transmission option with the Sasquatch Package, which includes the 2.7L EcoBoost engine. While this doesn't directly change the P0355 diagnosis, it introduces a new powertrain combination to the market.
• 2021-2024: SSM 52342 specifically notes build dates for affected Bronco Raptors as 'on and before 13-Feb-2024', suggesting that vehicles built after this date may have corrected PCM software from the factory.