As a seasoned auto repair expert at autelfrance.com, I’m here to break down the OBD-II trouble code P0355, specifically focusing on diagnosing and resolving issues related to “Ignition Coil E Primary/Secondary Circuit Malfunction.” This guide is designed to help both professional technicians and informed vehicle owners understand and tackle this common diagnostic code.
Understanding the P0355 Code
The P0355 code is a generic powertrain code, meaning it’s applicable across a wide range of OBD-II equipped vehicles. It signals a problem within the ignition coil “E” circuit. Modern vehicles often utilize a Coil-On-Plug (COP) ignition system, which eliminates traditional spark plug wires by placing individual ignition coils directly above each spark plug. These coils are controlled by the Powertrain Control Module (PCM).
Each COP unit typically has two dedicated wires: a power supply from the vehicle’s power distribution center and a driver circuit connected to the PCM. The PCM activates and deactivates the coil by grounding and ungrounding this driver circuit. The PCM constantly monitors these driver circuits for any electrical faults.
When the PCM detects an open circuit or a short circuit in the driver circuit for ignition coil “E” (note that “E” refers to a specific cylinder, often cylinder #5, but consult your vehicle’s service manual for exact designation), it sets the P0355 trouble code. In some vehicles, the PCM might also disable the fuel injector for that cylinder to prevent further issues.
Symptoms of a P0355 DTC
When the P0355 code is present, you may observe several symptoms:
- Malfunction Indicator Lamp (MIL) Illumination: The check engine light will typically turn on.
- Engine Misfire: This is a common symptom and can range from subtle to severe. You might notice rough idling, hesitation during acceleration, or a general lack of engine power. The misfire can be constant or intermittent depending on the nature of the fault.
Image: Diagram illustrating a typical Coil-On-Plug (COP) ignition system, highlighting the components involved in a P0355 fault.
Potential Causes of a P0355 Code
Several factors can trigger a P0355 code. Here are the most common culprits:
- Short to Voltage or Ground on COP Driver Circuit: A wiring fault where the driver circuit wire is making unintended electrical contact.
- Open Circuit on COP Driver Circuit: A break in the wiring of the driver circuit, preventing proper signal flow.
- Loose Connection at Coil or Damaged Connector: Poor electrical connection at the ignition coil connector or broken connector locking mechanisms.
- Faulty Ignition Coil (COP): The ignition coil itself may be internally damaged and malfunctioning.
- Faulty Powertrain Control Module (PCM): In rare cases, the PCM’s internal driver for the ignition coil may be defective.
Diagnosing and Resolving the P0355 Code
Troubleshooting P0355 requires a systematic approach. Here’s a step-by-step guide:
1. Initial Inspection and Intermittent Misfire Check:
Begin by noting if the engine is currently misfiring. If the misfire is intermittent, the issue might be related to loose wiring or connections. Perform a wiggle test:
- Wiggle Test: With the engine running, gently wiggle the wiring harness at the ignition coil “E” and along its path towards the PCM. Also, check the coil connector itself for looseness.
- Observation: If wiggling the wiring causes the misfire to appear or worsen, you’ve likely pinpointed a wiring issue. Inspect the harness for signs of chafing, damage, or improper routing. Repair any wiring faults as needed.
- Connector Check: Carefully examine the ignition coil connector for corrosion, bent pins, or broken locks. Clean or repair the connector as necessary.
2. Driver Signal Verification (Engine Misfiring):
If the engine is currently misfiring, proceed with these steps:
-
Disconnect Coil Connector: Turn off the engine and disconnect the wiring connector from ignition coil “E”.
-
Driver Signal Test: Restart the engine. We need to check if the PCM is sending a driver signal to the coil.
- Using a Voltmeter (AC Hertz): If you don’t have an oscilloscope, a voltmeter with an AC Hertz (Hz) function can be used. Set your voltmeter to the AC Hertz scale and probe the driver circuit terminal at the ignition coil connector (the connector side, not the coil side). Look for a frequency reading, typically between 5 and 20 Hz. This indicates the PCM is attempting to ground and unground the circuit to fire the coil.
- Using an Oscilloscope (Ideal Method): An oscilloscope provides a visual representation of the driver signal, allowing for a more detailed analysis of the waveform. Connect the oscilloscope to the driver circuit terminal and observe the pattern. A pulsing waveform indicates a functioning driver signal.
-
Interpretation of Driver Signal Test:
- Frequency Signal Present (or Pulsing Waveform on Scope): If you detect a driver signal, it indicates the PCM is likely functioning correctly, and the issue is likely with the ignition coil itself. Replace ignition coil “E”.
- No Frequency Signal (or No Waveform on Scope): If there’s no driver signal, proceed to the next step to check for voltage on the driver circuit.
3. Voltage Check on Driver Circuit (No Driver Signal):
- DC Voltage Check: With the ignition coil connector still disconnected and the engine running (or ignition in the “ON” position), use a voltmeter set to DC Voltage. Probe the driver circuit terminal at the ignition coil connector (connector side).
- Voltage Reading Present: If you measure any significant DC voltage on the driver circuit, it indicates a short to voltage somewhere in the wiring. Trace the driver circuit wiring to locate and repair the short to voltage.
- No Voltage Reading: If there is no voltage, proceed to the next step to check for circuit continuity and shorts to ground.
4. Continuity and Resistance Checks (Ignition OFF):
-
Turn Ignition OFF: Ensure the ignition is completely off.
-
Disconnect PCM Connector: Locate and disconnect the PCM connector. Refer to your vehicle’s service manual for the PCM location and connector pinout.
-
Continuity Test (Driver Circuit): Use a multimeter in continuity mode to check for continuity between the driver circuit terminal at the ignition coil connector and the corresponding driver circuit pin at the PCM connector.
- No Continuity: If there’s no continuity, there’s an open circuit in the driver wire. Inspect the wiring harness for breaks or damage and repair the open circuit.
- Continuity Present: If continuity is good, proceed to check for a short to ground.
-
Resistance to Ground Test (Driver Circuit): With the PCM still disconnected, use a multimeter in resistance mode. Measure the resistance between the driver circuit terminal at the ignition coil connector and a known good ground (e.g., vehicle chassis).
- Low Resistance (or Continuity): If you measure low resistance or continuity to ground, there’s a short to ground in the driver circuit. Locate and repair the short to ground.
- Infinite Resistance: Infinite resistance is expected, indicating no short to ground.
5. PCM Driver Fault (Suspect if all wiring checks pass):
- PCM as Last Resort: If all wiring tests are normal (no shorts, opens, or voltage issues) and there’s still no driver signal to the ignition coil, a faulty PCM driver is a possibility.
- Caution: PCM failure is less common and can be expensive. Before replacing the PCM, re-verify all wiring checks to rule out any overlooked wiring problems.
- Post-PCM Replacement Check: If you replace the PCM, it’s crucial to re-perform the wiring checks to ensure there wasn’t an underlying wiring issue that might have caused the original PCM failure. This helps prevent repeat failures.
6. PCM Monitoring System Fault (Rare):
- Misfire Absent, Code Resets: In rare instances, if the engine is not misfiring, the coil is being triggered correctly, but the P0355 code keeps resetting, there’s a possibility of a fault within the PCM’s coil monitoring system itself. This is a less frequent scenario and often points towards a PCM issue.
Important Note: This information is for general guidance only. Always consult your vehicle’s specific service manual for detailed diagnostic procedures and wiring diagrams. Incorrect diagnosis or repairs can lead to further damage or safety issues. If you are not comfortable performing these tests, it is recommended to seek assistance from a qualified automotive technician.
By following these diagnostic steps, you can effectively troubleshoot and resolve the P0355 code, addressing ignition coil “E” circuit malfunctions and restoring your vehicle’s optimal engine performance.
