The P0355 diagnostic trouble code (DTC) indicates a problem with the control circuit for ignition coil #5. Modern vehicles rely heavily on individual ignition coils to generate the spark necessary for combustion. When the engine control module (ECM) detects an issue with the electrical circuit controlling coil #5, this code is triggered, potentially leading to engine misfires and performance problems. Properly diagnosing and resolving this issue is crucial for maintaining optimal engine operation and preventing further damage.
The presence of a P0355 code isn't just an annoyance; it signals a potential breakdown in the engine's combustion process. Ignoring this code can lead to reduced fuel efficiency, rough idling, and even damage to the catalytic converter if unburnt fuel enters the exhaust system. Therefore, understanding the causes, symptoms, and troubleshooting steps associated with P0355 is vital for any vehicle owner or technician.
| Topic | Description | Possible Causes |
|---|---|---|
| Code Definition | P0355 indicates a fault within the control circuit specifically for ignition coil #5. This means the ECM has detected an unexpected voltage or current reading in the circuit that triggers the coil. The circuit includes wiring, connectors, and the coil itself. | Shorted or open wiring in the ignition coil control circuit; faulty ignition coil; loose or corroded connectors; faulty ECM (rare). |
| Symptoms | Observable signs that indicate a P0355 code is present. These symptoms can range from subtle to severe and might vary depending on the vehicle and the severity of the issue. Identifying these symptoms early can help in faster and more accurate diagnosis. | Engine misfire (most common); rough idling; decreased fuel economy; lack of power; check engine light illumination; possible engine stalling; catalytic converter damage (if misfire is prolonged). |
| Common Causes | The most frequent reasons for the P0355 code to appear. These are the culprits that are most often found during the troubleshooting process. Addressing these common causes first can save time and effort in the diagnostic process. | Faulty ignition coil; damaged or corroded wiring and connectors; loose connections; rodent damage to wiring. |
| Diagnostic Steps | A structured approach to identifying the root cause of the P0355 code. This involves a series of tests and inspections to isolate the problem. Following these steps systematically will ensure a thorough and accurate diagnosis. | Visual inspection of wiring and connectors; testing ignition coil resistance; checking for spark; using a multimeter to test circuit voltage and continuity; swapping ignition coils; ECM testing (last resort). |
| Repair Procedures | The actions taken to fix the issues identified during the diagnostic process. These can range from simple repairs to more complex component replacements. Proper repair procedures are essential to ensure the issue is resolved correctly and permanently. | Replacing the faulty ignition coil; repairing or replacing damaged wiring and connectors; cleaning corroded connections; securing loose connections; replacing the ECM (if diagnosed as the cause). |
| Related Codes | Other DTCs that may appear alongside P0355, potentially indicating a broader issue or providing additional clues to the problem. Understanding these related codes can help in a more comprehensive diagnosis. | P0300 (Random Misfire Detected); P0305 (Cylinder 5 Misfire Detected); P0351-P0360 (Ignition Coil A-J Primary/Secondary Circuit Malfunction); P0356, P0357, P0358, P0359, P0360 (Other ignition coil circuit malfunctions). |
| Tools Required | The specific tools needed to perform the diagnostic and repair procedures. Having the right tools on hand will make the process more efficient and effective. | OBD-II scanner; multimeter; spark tester; wiring diagram; socket set; wrench set; electrical tape; wire stripper/crimper; dielectric grease. |
| Safety Precautions | Essential safety measures to take while working on the vehicle's electrical system. These precautions will help prevent injury and damage to the vehicle. | Disconnect the negative battery terminal before working on the electrical system; wear safety glasses; avoid working in wet conditions; use caution when working near the ignition system due to high voltage. |
| ECM Role | The engine control module's function in managing the ignition coils. The ECM is the central computer that controls various engine functions, including ignition timing and coil activation. Understanding the ECM's role is crucial for understanding the P0355 code. | The ECM provides a ground signal to the ignition coil to trigger the spark. It monitors the current flow in the control circuit to ensure proper operation. If the ECM detects an abnormality in the control circuit for coil #5, it sets the P0355 code. |
| Wiring Diagram Significance | How wiring diagrams assist in diagnosing P0355. Wiring diagrams are essential tools for tracing circuits and identifying potential breaks or shorts. | A wiring diagram shows the specific wiring layout for the ignition coil #5 control circuit, allowing you to trace the wires from the ECM to the coil and identify potential points of failure, such as connectors and splices. |
Detailed Explanations
Code Definition: P0355, Ignition Coil 5 Control Circuit, signifies that the vehicle's ECM has detected a malfunction within the electrical circuit that controls ignition coil number five. This circuit typically includes the wiring, connectors, and the ignition coil itself. The ECM monitors the voltage and current flow in this circuit, and if it detects an unusual reading (e.g., an open circuit, a short to ground, or a short to voltage), it will set the P0355 code.
Symptoms: Several symptoms can indicate the presence of a P0355 code. The most common symptom is an engine misfire, which occurs when cylinder #5 is not firing correctly. This can lead to rough idling, where the engine shakes or vibrates excessively at idle. You might also experience decreased fuel economy due to the inefficient combustion process. A lack of power during acceleration is another possible symptom. The check engine light will illuminate on the dashboard. In severe cases, the engine may stall. Prolonged misfires can also lead to catalytic converter damage as unburnt fuel enters the exhaust system.
Common Causes: The most frequent causes of a P0355 code include a faulty ignition coil, which is the most likely culprit. Damaged or corroded wiring and connectors can also disrupt the electrical circuit. Loose connections can cause intermittent issues. Rodent damage to wiring is a common problem, especially in vehicles parked outdoors for extended periods.
Diagnostic Steps: A systematic approach is crucial for diagnosing a P0355 code. Start with a visual inspection of the wiring and connectors associated with ignition coil #5. Look for any signs of damage, corrosion, or loose connections. Next, test the ignition coil resistance using a multimeter, comparing the reading to the manufacturer's specifications. Check for spark at the spark plug of cylinder #5 using a spark tester. Use a multimeter to test circuit voltage and continuity, ensuring that the wiring is intact and that the coil is receiving power and ground. Swapping ignition coils with a known good coil from another cylinder can help determine if the coil itself is faulty. ECM testing should be performed as a last resort, as ECM failures are relatively rare.
Repair Procedures: Once the cause of the P0355 code has been identified, the appropriate repair procedure can be performed. Replacing the faulty ignition coil is a common repair. Repairing or replacing damaged wiring and connectors is essential to restore the integrity of the electrical circuit. Cleaning corroded connections with electrical contact cleaner can improve conductivity. Securing loose connections will prevent intermittent issues. Replacing the ECM should only be done if it has been definitively diagnosed as the cause of the problem, and this often requires specialized equipment and expertise.
Related Codes: Several other DTCs may appear alongside P0355. P0300 (Random Misfire Detected) indicates that misfires are occurring in multiple cylinders. P0305 (Cylinder 5 Misfire Detected) specifically identifies a misfire in cylinder #5. P0351-P0360 (Ignition Coil A-J Primary/Secondary Circuit Malfunction) codes indicate similar issues with other ignition coils. Understanding these related codes can provide valuable context for diagnosing the root cause of the problem.
Tools Required: Several tools are essential for diagnosing and repairing a P0355 code. An OBD-II scanner is needed to read and clear the DTC. A multimeter is used to test voltage, resistance, and continuity. A spark tester is used to check for spark at the spark plug. A wiring diagram provides a detailed map of the electrical circuit. A socket set and wrench set are needed to remove and install components. Electrical tape and a wire stripper/crimper are used to repair wiring. Dielectric grease helps prevent corrosion on electrical connections.
Safety Precautions: Before working on the vehicle's electrical system, disconnect the negative battery terminal to prevent electrical shock. Wear safety glasses to protect your eyes. Avoid working in wet conditions to minimize the risk of electrocution. Use caution when working near the ignition system due to the presence of high voltage.
ECM Role: The ECM plays a crucial role in managing the ignition coils. It provides a ground signal to the ignition coil to trigger the spark. The ECM monitors the current flow in the control circuit to ensure proper operation. If the ECM detects an abnormality in the control circuit for coil #5, it sets the P0355 code. The ECM relies on feedback from sensors to adjust ignition timing and coil dwell time, optimizing engine performance.
Wiring Diagram Significance: A wiring diagram is invaluable for diagnosing P0355. It shows the specific wiring layout for the ignition coil #5 control circuit, allowing you to trace the wires from the ECM to the coil and identify potential points of failure, such as connectors, splices, and grounding points. By following the wiring diagram, you can systematically check the continuity and voltage of each wire in the circuit, pinpointing the location of the fault.
Frequently Asked Questions
What does the P0355 code mean? It indicates a problem with the control circuit for ignition coil #5, meaning the ECM has detected an issue with the electrical signal controlling that coil.
Can I drive with a P0355 code? It's not recommended. The misfire can damage the catalytic converter and lead to further engine problems.
How do I fix a P0355 code? Start by inspecting the wiring and connectors, then test the ignition coil and circuit with a multimeter. Replacing a faulty coil or repairing damaged wiring are common solutions.
Is the ignition coil always the problem with P0355? Not always, but it's a common cause. Wiring issues, connectors, and even (rarely) the ECM can also be responsible.
Where is ignition coil #5 located? The location varies by engine. Consult your vehicle's repair manual or a reliable online resource to determine the exact location.
Conclusion
The P0355 code signals a problem within the ignition coil #5 control circuit, often leading to engine misfires and performance issues. By systematically diagnosing the problem, addressing common causes like faulty ignition coils or wiring issues, and performing appropriate repairs, you can resolve the P0355 code and restore optimal engine operation.