P1355

What Does Code P1355 Mean?

The OBD-II diagnostic trouble code P1355 indicates a detected malfunction within the primary circuit of the ignition coil designated as “D”. The Engine Control Module (ECM), often interchangeably referred to as the Powertrain Control Module (PCM), is responsible for continuously monitoring the electrical characteristics and operational feedback of the ignition system components. In a typical electronic ignition system, the primary circuit of an ignition coil consists of a low-voltage winding (the primary winding), which receives battery voltage (B+) on one side and is grounded through a switching transistor (or “driver”) within the ECM on the other side. When the ECM grounds this circuit, current flows through the primary winding, creating a magnetic field. When the ECM then rapidly opens this ground circuit, the magnetic field collapses, inducing a very high voltage in the secondary winding, which subsequently fires the spark plug.

Code P1355 is set when the ECM detects an electrical fault within this primary control circuit for coil “D”. This fault could manifest as an open circuit (no current flow), a short circuit to ground, or a short circuit to voltage, indicating an abnormal current draw or absence of current flow through the primary winding that deviates from programmed parameters. The specific cylinder “D” refers to depends on the vehicle manufacturer’s cylinder numbering and coil assignment scheme, but it typically corresponds to the fourth cylinder in the firing order or sequential numbering (e.g., cylinder #4).

Common Symptoms

• Check Engine Light (CEL) Illumination: The most common and immediate symptom, indicating the ECM has detected a fault.
• Engine Misfire: The primary consequence of a faulty ignition coil or its circuit is the inability to produce a spark, leading to misfires on the affected cylinder. This is often accompanied by specific misfire codes (e.g., P030D, where D represents the cylinder number).
• Rough Idling or Stalling: Due to the engine running on fewer cylinders, the idle quality will deteriorate significantly.
• Reduced Engine Performance: Noticeable loss of power, poor acceleration, and hesitation, especially under load.
• Poor Fuel Economy: Unburnt fuel passing through the affected cylinder due to lack of spark can also lead to increased fuel consumption.
• Strong Fuel Odor: Unburnt fuel entering the exhaust system can cause a noticeable smell of raw gasoline.
• Difficulty Starting: In some cases, a persistent misfire can make the engine harder to start, though this is less common for a single-cylinder issue.

What Causes the Code P1355?

• Faulty Ignition Coil (Coil “D”): The most common cause, where the internal primary winding develops an open circuit, a short circuit, or experiences excessive resistance, preventing proper magnetic field generation.
• Damaged Wiring or Connector for Coil “D”:
  • Open Circuit: A broken wire in the primary feed (B+) or the control signal wire to the ECM.
  • Short to Ground: The primary circuit wiring chafing and making contact with the vehicle’s chassis or engine block.
  • Short to Voltage: The primary control wire accidentally making contact with another power supply wire.
  • Corrosion or Loose Connections: At the coil connector or harness, leading to intermittent or high-resistance connections.
• Failed ECM/PCM Driver: The specific transistor or driver circuit within the ECM responsible for controlling the ground path for Coil “D” fails. This is less common than coil or wiring faults but is a definitive possibility, especially if power and ground to the coil are confirmed good, and the coil itself tests fine.
• Faulty Spark Plug (Less Common as a direct cause, but can lead to coil failure): While a faulty spark plug (e.g., fouled or gapped incorrectly) typically triggers misfire codes directly, severe issues can sometimes overload and prematurely damage the ignition coil’s primary circuit over time, though it rarely causes P1355 directly.

How to Diagnose and Troubleshoot

A systematic approach is crucial for diagnosing P1355. Always consult the vehicle’s specific service information for accurate wiring diagrams, component locations, and resistance specifications.

1. Retrieve and Analyze DTCs and Freeze Frame Data: Use an OBD-II scanner to confirm P1355. Note any other related codes, especially misfire codes (e.g., P0304 if Coil D corresponds to cylinder 4). Review freeze frame data to understand engine conditions (RPM, load, temperature) when the code was set. Clear codes after initial review.
2. Visual Inspection:
   • Carefully inspect the ignition coil “D” and its electrical connector. Look for visible damage, cracks, oil leaks, or signs of overheating on the coil body.
   • Examine the wiring harness leading to the coil for chafing, cuts, bare wires, or signs of rodent damage. Pay close attention to areas where the harness might rub against engine components.
   • Check for corrosion or bent pins within the coil connector itself. Ensure the connector is securely seated.
3. Perform a Coil Swap Test (if applicable to Coil-On-Plug systems): If the vehicle uses individual Coil-On-Plug (COP) coils, swap Coil “D” with a known good coil from an adjacent, healthy cylinder (e.g., Coil “D” with Coil “C”). Clear codes, start the engine, and see if the misfire and the P1355 code follow the coil to the new cylinder. If the misfire or code moves, the coil is faulty. If the code stays on cylinder “D”, the issue is likely wiring or ECM related.
4. Electrical Testing with a Digital Multimeter (DMM):
   • Power Supply Check (Coil B+): With the ignition ON and engine OFF, disconnect the coil “D” electrical connector. Using a DMM set to DC Volts, check for battery voltage (approximately 12V) between the B+ terminal of the coil harness connector and a good chassis ground. If no voltage, diagnose the power supply circuit (fuse, relay, wiring).
   • Ground Reference Check: Identify the constant ground wire (if applicable, separate from the ECM control ground) in the coil connector and test for continuity to chassis ground (should be < 0.5 ohms).
   • ECM Control Circuit Check: This circuit carries the switching signal from the ECM.
     • Continuity Test: Disconnect the ECM connector and the coil “D” connector. Identify the control wire for coil “D” at both ends using a wiring diagram. Test for continuity between the corresponding pins (should be < 0.5 ohms). Also, test for shorts to ground and shorts to B+ on this wire (should be infinite resistance).
     • Signal Test (Advanced, requires Oscilloscope): Reconnect the ECM. With the engine running, back-probe the control wire at the coil connector. An oscilloscope should show a square wave signal, indicating the ECM is attempting to switch the coil ground. The duty cycle and voltage swing should be consistent with a healthy primary circuit operation. A DMM can sometimes show an average voltage, but an oscilloscope is definitive.
   • Coil Primary Resistance Test: If specifications are available, measure the resistance of the primary winding of coil “D” using the DMM (ignition OFF, coil disconnected). Compare this reading to factory specifications or to a known good coil. An open circuit (OL) or a significantly out-of-spec resistance indicates a faulty coil.
5. ECM Driver Diagnosis: If all coil and wiring tests confirm good power, ground, and continuity, and the coil itself tests good, but no control signal is present from the ECM, the issue points towards a failed ignition coil driver within the ECM. This should be a last resort conclusion after thoroughly eliminating all other possibilities.

Recommended Repairs and Solutions

The recommended repair depends entirely on the findings from the diagnostic procedure:

• Replace Ignition Coil “D”: If the coil swap test confirmed the fault followed the coil, or if direct electrical testing of the coil (e.g., primary resistance) indicated it was faulty, replace Coil “D”. Always ensure the spark plug in that cylinder is also in good condition; a worn or fouled plug can overstress a new coil.
• Repair or Replace Wiring Harness: If visual inspection or DMM tests revealed an open circuit, a short, or excessive resistance in the wiring to or from Coil “D”, repair the damaged section of the harness. Use proper automotive-grade wiring, connectors, and heat-shrink tubing for durable repairs. In severe cases, replacing a section of the harness may be necessary. Ensure all connections are secure and free of corrosion.
• Replace ECM/PCM: If all other components (coil, wiring, power, ground) test conclusively good, and an oscilloscope confirms no control signal from the ECM to Coil “D”, then the ECM’s internal driver for that circuit is likely faulty. ECM replacement is a complex and often costly repair that typically requires programming or “flashing” to the vehicle’s specific VIN and options. This step should only be taken after all other diagnostic avenues have been exhausted.

Mechanics’ Tips:

• Always identify the correct cylinder “D” for the specific vehicle using service information. Cylinder numbering varies between manufacturers.
• When replacing ignition coils, consider replacing all spark plugs, especially if they are nearing their service interval. Ensure correct spark plug type and gap.
• Use high-quality OEM or reputable aftermarket ignition coils. Cheap coils often have a shorter lifespan and can lead to recurring issues.
• After completing any repair, clear the diagnostic trouble codes from the ECM and perform a test drive under various engine loads and RPMs to confirm the repair and ensure the code does not return. Check for pending codes before returning the vehicle.
• Ensure all connectors are fully seated and locked, and any removed components (e.g., intake manifold, brackets) are reinstalled correctly to prevent future issues.