Finding “Ignition Coil D”: What It Means and Where to Look

In most vehicles, “Ignition Coil D” refers to the coil for cylinder 4, located directly on or above that spark plug; however, the exact physical spot depends on your engine layout and manufacturer’s cylinder numbering. This means Coil D could be at the far end of an inline engine or mid/front on a V-engine, so confirming your specific cylinder map is essential.

What “Ignition Coil D” Typically Signifies

Automakers and scan tool software commonly label individual coils alphabetically in cylinder order: A, B, C, D, and so on. Across many brands, the letter D corresponds to cylinder 4, which is why OBD-II code P0354 is defined as “Ignition Coil D Primary/Secondary Circuit” on numerous platforms. The physical location of that cylinder changes with engine configuration (inline vs. V) and manufacturer numbering schemes.

How Cylinder Numbering Affects Coil D’s Location

The following list outlines common conventions for how cylinder positions are arranged, which determines where Coil D (often cylinder 4) actually sits on the engine.

• Inline-4 (I4): Cylinders run in a straight line. Cylinder 1 is usually at the timing belt/chain end. Cylinder 4 sits at the opposite end—often the transmission side on a transverse FWD layout.
• Inline-6 (I6): Cylinder 1 at the timing end; cylinder 4 is the fourth from that end, roughly mid-to-rear of the straight bank.
• V6 (varies by brand): Even cylinders (2-4-6) occupy one bank and odd (1-3-5) the other. Example patterns:
  – Toyota/Lexus V6 (e.g., 2GR-FE): Bank 1 (1-3-5) typically at the firewall; Bank 2 (2-4-6) at the radiator side; cylinder 4 is the middle of the front bank.
  – GM V6: Bank 1 often driver side (odd cylinders); Bank 2 passenger side (even cylinders); cylinder 4 is middle of the passenger bank.
• V8 (varies by brand):
  – GM/Chevy LS: Bank 1 is driver side (1-3-5-7); Bank 2 passenger (2-4-6-8); cylinder 4 is front half of passenger bank.
  – Ford Modular: Bank 1 is passenger side (1-2-3-4); Bank 2 driver (5-6-7-8); cylinder 4 is rear of passenger bank.
  – Many Toyota/Nissan V8s: Bank 1 typically passenger side; even cylinders on the opposite bank place cylinder 4 on the driver side front half.
• General rule: Bank 1 always contains cylinder 1, but which physical side is Bank 1 depends on the manufacturer.

Because V-engine bank orientation differs across makes, blindly assuming sides can mislead you; always verify with your vehicle’s service information or under-hood labels.

Coil-On-Plug vs. Coil Pack: What You’re Looking For

Modern engines often use coil-on-plug (COP), where each spark plug has its own coil mounted directly on top—so “Coil D” is the fourth COP in cylinder order. Older or some budget engines use a coil pack (a multi-tower unit) with plug wires; in that case, “Coil D” would be the coil circuit feeding cylinder 4’s plug wire from the pack.

Step-by-Step: How to Locate Ignition Coil D on Your Vehicle

Use the steps below to identify and physically find Coil D with minimal guesswork and without relying on inconsistent online diagrams.

1. Confirm what “D” maps to: Check your scan tool’s data or a factory service manual. On most OBD-II systems, D = cylinder 4 (e.g., P0354).
2. Identify the engine layout: Inline or V? Look at the valve cover(s). One cover means inline; two covers means V engine.
3. Find cylinder 1: On inline engines, cylinder 1 is at the timing belt/chain end. On V engines, cylinder 1’s bank is “Bank 1” (location varies by brand).
4. Use the cylinder map: Follow the manufacturer’s numbering (often on an under-hood emissions label, service manual, or reputable OEM guide) to locate cylinder 4.
5. Locate the coil:
   – COP systems: The coil is the black module bolted atop the spark plug for cylinder 4, with a single electrical connector.
   – Coil pack systems: Trace the plug wire labeled/known for cylinder 4 from the distributor/coil pack to the spark plug; the corresponding coil circuit is “D.”
6. Verify by swapping: If diagnosing a misfire, swap the suspected coil with another cylinder and see if the fault code moves—this confirms you found the correct coil position.

Following this sequence avoids common mistakes, especially on transverse engines where “left/right” and “front/rear” can be misleading relative to the car rather than the engine.

Where to Find Reliable Cylinder Diagrams

The resources below commonly provide accurate cylinder numbering and bank orientation for your exact year/make/model/engine code.

• Factory service manual (FSM) or OEM online service portals.
• Under-hood emissions/vacuum diagram labels (often show Bank 1/2).
• Reputable repair databases (Alldata, Mitchell1, OEMTechInfo sites).
• Owner forums with verified service manual excerpts (exercise caution; confirm with OEM sources).

When diagrams disagree, defer to OEM documentation or the emissions label under the hood, which reflects your specific engine orientation and bank assignment.

What If Your Vehicle Doesn’t Follow A=1, B=2, C=3, D=4?

Most do, but not all scan tools or manufacturers present coils by letter. Some use cylinder numbers only, others label by connector position. If your tool flags “Coil D” yet your manual shows a different mapping, rely on the manual’s cylinder identification and wiring pinout for final confirmation.

Red Flags and Tips

Keep these practical notes in mind to avoid misidentification and repeat repairs.

• Transverse engines: “Front of engine” means the belt/chain end, not the grille side.
• Bank 1 confusion: It’s the bank with cylinder 1—brand-dependent in physical location.
• Coil connector reach: Harness length often hints at intended coil positions.
• Codes and misfires: P0354 points to the coil circuit for D (often cylinder 4), but a failing plug or wiring can cause the same code—test before replacing parts.

By aligning code definitions with verified cylinder maps and a quick swap test, you can pinpoint Coil D confidently and rule out related faults.

Bottom Line

Ignition Coil D is generally the coil for cylinder 4, positioned directly above that spark plug on COP systems or tied to that plug’s lead on coil-pack systems. Its physical location varies with engine layout and manufacturer cylinder numbering. To be exact for your car, consult the under-hood label and the factory service manual to identify cylinder 4’s position, then locate the corresponding coil.

Summary

Coil D typically equals cylinder 4, but the exact spot depends on your engine type and brand-specific cylinder maps. Verify the cylinder layout from OEM sources, identify cylinder 4 based on that map, and then locate the coil sitting atop (COP) or feeding (coil pack) that cylinder. When in doubt, confirm by swapping coils and watching whether the fault follows.

Where is my ignition coil located?

Your ignition coil is located on the engine, most often on top of the valve cover and directly above the spark plug, where it receives a signal from the engine computer to fire the spark plug. In older cars, the ignition coil might be inside a distributor, but in newer cars with modern electronic systems, you’ll typically find individual coil-on-plug systems, meaning each spark plug has its own coil. 
To find it:

1. Open the hood: and locate the engine. 
2. Look for the ignition coils: on top of the engine’s valve covers. They’re usually obvious because each one will be connected to a spark plug. 
3. Identify the spark plug: for the cylinder you’re interested in, and then you’ll see the ignition coil sitting directly on top of it. 

Important Considerations

• Engine cover: Opens in new tabYou might need to remove a plastic engine cover or other components to access the coils. 
• Vehicle specifics: Opens in new tabThe exact placement can vary significantly depending on your car’s make and model, so consulting your vehicle’s owner’s manual or a shop manual is the best reference. 
• Type of system: Opens in new tabOlder vehicles with a distributor will have a single coil, while modern vehicles with coil-on-plug (COP) systems will have multiple coils. 

This video shows how to locate ignition coils on a Ford F150: 44sRams to the RescueYouTube · Mar 7, 2025

Which coil is ignition coil D?

cylinder #4 ignition coil
The powertrain control system (PCM) manages the ignition coils that ignite the spark plugs at precisely the right time. If the PCM detects a potential problem with the ignition coil “D” (which is the cylinder #4 ignition coil) or its circuit, code P0354 may be set.

How serious is the P0354 code?

A P0354 code means that the ignition coil or coils are not functioning properly and that there is an electrical problem with them. The ignition coils are responsible for properly igniting the air-fuel mixture in the engine’s combustion chambers.

Where is the ignition coil D on a 2005 Ford Escape?

2005 Ford Escape P0354 Code: Ignition Coil Location & Fix
On a 2005 Escape, the ignition coils are mounted on top of the engine, above each spark plug. Inspect the coil pack for damage or corrosion, check wiring connectors for secure fit, and test coil resistance with a multimeter.