P0354 on 2021-2024 Ford Bronco: Ignition Coil 'D' Circuit Malfunction Causes & Fixes

What's Unique About the 2021-2024 Ford BRONCO

For the 2021-2024 Ford Bronco, this code is particularly relevant due to known ignition system issues on the EcoBoost engine family. Ford has issued multiple Technical Service Bulletins (TSBs) for this generation, specifically mentioning DTCs like P0354 related to ignition coil failures on the 2.3L and 3.0L EcoBoost engines. Crucially, TSB SSM 52342 points out that the PCM software may incorrectly map the DTC to the wrong cylinder on vehicles built before mid-February 2024. This means that while P0354 points to cylinder #4, the actual fault could be on another cylinder, making a diagnostic power balance test (using a tool like FDRS) highly recommended before swapping parts.

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 (may be flashing)
• Rough or shaking idle
• Engine misfires, which may feel like a stumble or hesitation during acceleration
• Reduced engine power and responsiveness
• Difficulty starting the engine
🎬 Watch: A breakdown of P0354 causes and common fixes
• Noticeable fuel smell from the exhaust

Most Likely Causes

1. Faulty Ignition Coil #4 🔴 High Probability → Shop Ignition Coil Ford has issued TSBs #TSB 24-2406 and #SSM 52342 acknowledging ignition coil circuit faults on 2.3L and 3.0L EcoBoost engines in this vehicle. Aftermarket coils are also a common source of premature failure, with many technicians recommending sticking to OEM Motorcraft parts.
   How to confirm: The easiest method is to swap the ignition coil from cylinder #4 with one from another cylinder (e.g., cylinder #1). Clear the codes and drive the vehicle. If the code changes to P0351, the ignition coil is confirmed to be faulty. However, due to the potential for incorrect cylinder mapping noted in TSB 52342, a cylinder power balance test with a capable scan tool is the most accurate diagnostic step.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace the corresponding spark plug at the same time and apply dielectric grease to the new coil boot. 🎬 Watch: Step-by-step EcoBoost coil pack replacement and misfire fix
   Est. part cost: $30-$80
2. Damaged Wiring or Connector 🟡 Medium Probability Engine heat and vibration can cause wiring to become brittle or connectors to loosen over time. The plastic locking tabs on the coil connectors are known to become brittle and break, leading to a poor connection. Rodents can also chew on wiring harnesses under the engine cover.
   How to confirm: Visually inspect the wiring harness and connector for cylinder #4's ignition coil. Look for any signs of cracks, corrosion, melting, or frayed wires. Ensure the connector is securely plugged in and that the locking tab is intact. Use a multimeter to check for battery voltage at the power pin and for good ground at the ground pin on the connector with the key on.
   Typical fix: Repair the damaged section of wire or replace the ignition coil pigtail connector. 🎬 See how to properly replace damaged Ford coil connectors Connector repair kits are available.
   Est. part cost: $15-$40
3. Worn or Faulty Spark Plug ⚪ Low Probability → Shop Spark Plug While a bad spark plug typically sets a misfire code (P0304), a severely worn or fouled plug can increase resistance in the secondary ignition circuit, potentially stressing the coil and contributing to a P035x code.
   How to confirm: Remove the spark plug from cylinder #4 and inspect it for wear, damage, or heavy deposits. Compare it to a new plug or one from a working cylinder. A large gap or fouling can indicate a problem. The correct spark plug gap is 0.028 in - 0.031 in (0.7 mm - 0.8 mm) for the 2.3L EcoBoost.
   Typical fix: Replace the spark plug. It's best practice to replace all spark plugs as a set, especially on a turbocharged engine.
   Est. part cost: $10-$25 per plug

Rare But Worth Checking

• Powertrain Control Module (PCM) Failure: → Shop Engine Control Module (ECM) This is very rare. A faulty coil driver within the PCM can cause this code. This should only be considered after all other possibilities (coil, plug, wiring) have been definitively ruled out through testing. TSB 52342 also mentions that a PCM software update may be required to correct cylinder mapping issues on some models.

Diagnosis Steps

1. Read the diagnostic trouble codes with an OBD-II scanner to confirm P0354 is present and check for any other related codes like P0304.
2. Crucial Step for Bronco: Be aware of TSB 52342, which indicates the PCM may report the wrong cylinder on certain models. If you have access to a Ford-specific diagnostic tool (like FDRS) or a high-end bidirectional scanner, perform a cylinder power balance test to confirm which cylinder is actually failing before proceeding.
3. Locate cylinder #4. On the 2.3L I4, it is the rearmost cylinder. On the 2.7L/3.0L V6, it is the frontmost cylinder on the driver's side (left bank).
4. Visually inspect the ignition coil, connector, and wiring for the suspect cylinder. Look for any obvious damage, corrosion, or loose connections. Check for oil in the spark plug well, which indicates a leaking valve cover gasket.
5. If no visual faults are found, perform an ignition coil swap test. Label and move the coil from the suspect cylinder to another cylinder (e.g., swap cylinder #4 and #1).
6. Clear the DTCs using the scanner.
7. Start the engine and let it run for a few minutes, or take a short drive to see if the Check Engine Light returns.
8. Re-scan for codes. If the code has moved to the new cylinder (e.g., P0351), the ignition coil is faulty and needs to be replaced.
9. If the original code (P0354) returns, the problem lies in the wiring or the PCM. Inspect the wiring harness for continuity and check for power and ground at the coil connector using a multimeter.
10. If the wiring is confirmed to be good, the issue may be with the PCM, which requires advanced diagnostics.

Parts You'll Likely Need

• Ignition Coil (OEM #JX6Z-12029-A (For 2.3L)) — This is the most frequent failure point for code P0354, especially on EcoBoost engines, as confirmed by Ford's own service bulletins. Owner forums and mechanic recommendations strongly advise using genuine Motorcraft parts over aftermarket brands to avoid premature failure.
  Trusted brands: Motorcraft (Recommended), NGK, Denso, Bosch
  OEM price range: $60-$90
  Aftermarket price range: $30-$60
• Ignition Coil (V6) (OEM #KT4Z-12029-A (For 2.7L/3.0L)) — The V6 engines use a different coil, but it is still the most common cause of this code on those engines. The same advice applies: use OEM Motorcraft coils for reliability.
  Trusted brands: Motorcraft (Recommended), Standard Motor Products
  OEM price range: $70-$100
  Aftermarket price range: $40-$70

Related Codes That Often Appear With This One

• P0304 — P0304 indicates a misfire detected on cylinder #4. Since P0354 points to a fault in the ignition coil circuit for that same cylinder, the lack of spark will directly cause a misfire.
• P0300 — Indicates random or multiple cylinder misfires. This can occur if the underlying issue, like a widespread wiring problem or fuel delivery issue, is affecting more than just cylinder #4.

Technical Service Bulletins (TSBs) & Recalls

• TSB 24-2406: Notes that 2021-2024 Broncos with 2.3L/3.0L EcoBoost engines may set various ignition system DTCs, including P0354.
• SSM 52342: Mentions that 2021-2024 Broncos with the 2.3L EcoBoost may set ignition system DTCs, including P0354. It specifically warns of incorrect cylinder-to-DTC mapping in the PCM and recommends a power balance test for accurate diagnosis.

Platform-Specific Known Issues

• Ford has issued Technical Service Bulletin #TSB 24-2406, which states that 2021-2024 Broncos with 2.3L or 3.0L EcoBoost engines may exhibit an illuminated MIL with ignition system DTCs including P0354.
• A similar bulletin, #SSM 52342, also notes that 2021-2024 Broncos with the 2.3L EcoBoost engine may set code P0354 and other ignition-related codes in the PCM. Crucially, this TSB warns that the PCM may have incorrect cylinder-to-DTC mapping, meaning the code could be for the wrong cylinder. It advises using a power balance test to identify the correct failing cylinder before replacing parts.
• Owner experiences on forums like Bronco6G confirm that ignition coil failure is a common issue. One owner of a 2.7L Badlands reported a P0354 code at around 30,000 miles, which was resolved by the dealer replacing the ignition coil and spark plug for cylinder 4 under warranty.

Mechanic-Grade Diagnostic Values

• Ignition Coil Connector - Power Pin Voltage (Key On, Engine Off) — expected: Battery Voltage (approx. 12.6V). Failure: Low or no voltage indicates a problem with the power supply circuit or fuse.
• Ignition Coil Connector - Ground Pin — expected: Good continuity to chassis ground (<1 Ohm). Failure: High resistance or an open circuit indicates a bad ground connection.
• Ignition Coil Connector - PCM Driver Signal (at idle) — expected: 5-20 Hz signal on a multimeter set to AC Hertz scale.. Failure: No signal suggests a wiring break or a faulty PCM driver.
• Ignition Coil Connector - PCM Driver Signal (Oscilloscope) — expected: A square wave with an amplitude of approximately 4-5 Volts.. Failure: A missing, weak, or malformed waveform points to a PCM or wiring issue.

Scan Tool Commands That Help

• Ford FDRS (or equivalent professional scanner): Power Balance Test — This is a critical first diagnostic step for this specific vehicle and code, as recommended by Ford TSB SSM 52342. It graphically displays the power contribution from each cylinder to accurately identify which one is truly at fault, bypassing a known software issue where the PCM may report the incorrect cylinder.

Wiring & Ground Locations

• Ignition Coil Connector (C169 for Cyl #4 on 2.3L) — On top of the valve cover, plugged into the ignition coil for the fourth cylinder (rearmost on 2.3L, front-left on V6).. This connector is the direct interface between the engine harness and the ignition coil. Testing for power, ground, and signal at its pins is the primary way to determine if the fault lies with the coil or the vehicle's wiring/PCM. The plastic locking tab is a common failure point, leading to a poor connection.
• Engine Ground Points (General) — Multiple locations, including battery-to-chassis, battery-to-engine-block, and engine-to-firewall. Specific locations like G110 and G120 are detailed in the factory service manual under 'Component Location Views'.. A poor engine ground can cause a host of intermittent electrical issues, including ignition problems. While not a direct cause of a single-cylinder coil code, it can create electrical noise and voltage drops that may trigger faults in the ignition monitoring system.

Real Owner Repair Stories

• Bronco6G Forum (2022 Ford Bronco Badlands 2.7L, approx. 30,000 miles) — Check Engine Light on, rough idle, P0354 code stored.
  ❌ Tried (didn't work) Owner did not report trying any fixes before taking it to the dealer.
  ✅ What actually fixed it The Ford dealership diagnosed a bad ignition coil on cylinder #4. They replaced both the ignition coil and the spark plug for that cylinder under warranty, which resolved the code and symptoms.

OEM Part Supersession History

• KT4Z-12029-A (V6 Coil) → N/A — N/A
  Heads up: Related part numbers for the 2.7L engine include FT4Z-12029-A and JT4Z-12029-A. This suggests variations exist based on model year or specific V6 application. Always verify the correct part number with a VIN before purchasing.

Model Year Variations Within This Range

• 2021-2024 (pre-Feb 2024 builds): According to TSB SSM 52342, Bronco models (specifically 2.3L and 3.0L Raptor) built on or before February 13, 2024, may have a PCM software issue that causes incorrect cylinder-to-DTC mapping. Vehicles built after this date likely have corrected software, making the P0354 code more reliable in pointing to the correct cylinder.