P1356 - IC Output High/Pulse Detected when GND_Cyl. 6

Introduction:

Diagnostic Trouble Code (DTC) P1356 indicates a specific issue related to the ignition system in a vehicle, specifically concerning the Integrated Circuit (IC) output signal when cylinder 6 is grounded. This code suggests that the Powertrain Control Module (PCM) has detected an unexpected high voltage or pulse signal from the ignition control circuit for cylinder 6 when that cylinder is theoretically grounded, signaling a potential fault within the ignition system or its related circuitry. Addressing this code promptly is important to maintain engine performance and prevent potential damage.

Table: P1356 Diagnostic Information

Detailed Explanations

Code Definition: IC Output High/Pulse Detected when GND_Cyl. 6

This diagnostic code is triggered when the vehicle's PCM detects an abnormal voltage or pulse signal emanating from the ignition control circuit associated with cylinder 6 while the cylinder is grounded. This is not the expected behavior and indicates a discrepancy between what the PCM commands and what it actually observes. The "IC Output" refers to the signal coming from the ignition control circuit, often located within the ignition module or PCM itself. "GND_Cyl. 6" means the PCM is expecting cylinder 6 to be electrically grounded as part of its normal ignition sequence.

Affected Systems: Ignition System, Powertrain Control Module (PCM)

The P1356 code directly relates to the ignition system because it involves the ignition coil and its control circuitry for cylinder 6. The Powertrain Control Module (PCM) is also implicated, as it's responsible for monitoring the ignition system's performance and setting the code when it detects anomalies. The PCM controls the timing and firing of the ignition coils and relies on feedback signals to ensure proper operation. Any fault in the PCM's ability to interpret or control these signals can lead to a P1356 code.

Symptoms: Misfire on cylinder 6, rough idling, decreased engine performance, illuminated Check Engine Light (CEL), hard starting, stalling.

The most common symptom is a misfire on cylinder 6. This occurs because the incorrect or absent ignition signal prevents the proper combustion of the air-fuel mixture in that cylinder. This misfire can lead to rough idling, as the engine struggles to maintain a smooth and consistent speed. Consequently, overall engine performance suffers, resulting in reduced power and acceleration. The Check Engine Light (CEL) will illuminate, signaling to the driver that a problem has been detected. In more severe cases, the vehicle may experience hard starting or even stalling, especially at low speeds.

Possible Causes: Ignition coil, wiring harness, connectors, PCM, grounding issues, crankshaft position sensor, camshaft position sensor.

• Faulty Ignition Coil: The ignition coil for cylinder 6 is the most likely culprit. A shorted or open coil can cause incorrect signals.
• Damaged Wiring/Connectors: Damaged or corroded wiring and connectors in the ignition circuit for cylinder 6 can disrupt the signal path and lead to false readings.
• PCM Malfunction: Though less common, a malfunctioning PCM can incorrectly interpret the ignition signals or send erroneous commands.
• Poor Grounding: Inadequate grounding of the ignition system or PCM can cause erratic signals and trigger the code.
• Crankshaft Position Sensor/Camshaft Position Sensor: While not directly related, a faulty crankshaft or camshaft position sensor can provide inaccurate engine timing information, indirectly impacting the ignition system and potentially contributing to the P1356 code.

Troubleshooting Steps

1. Visual Inspection: Begin by thoroughly inspecting the wiring harness and connectors associated with the ignition coil for cylinder 6. Look for signs of damage, corrosion, or loose connections. Pay close attention to the wiring insulation for cracks or breaks.

2. Ignition Coil Test: Use a multimeter to test the resistance of the ignition coil for cylinder 6. Compare the readings to the manufacturer's specifications. Also, check for shorts to ground.

3. Wiring Continuity Test: Using a multimeter in continuity mode, check the wiring between the ignition coil and the PCM. Ensure there are no open circuits or shorts to ground.

4. Grounding Check: Verify that the engine and PCM are properly grounded. Clean and tighten any ground connections that appear corroded or loose. A voltage drop test can be performed to check the effectiveness of the ground circuits.

5. PCM Diagnosis: If the other components appear to be functioning correctly, the PCM may be the source of the problem. Consult a qualified technician for PCM diagnosis and potential reprogramming or replacement.

6. Crankshaft/Camshaft Position Sensor Check: Although less likely, rule out issues with the crankshaft and camshaft position sensors by testing their signal output using an oscilloscope or scan tool.

Prevention

• Regular Maintenance: Following the manufacturer's recommended maintenance schedule can help prevent ignition system problems.
• Wiring Inspection: Periodically inspect the wiring harness and connectors for signs of damage or corrosion.
• Grounding Maintenance: Ensure that all ground connections are clean and tight.
• Quality Parts: When replacing ignition system components, use high-quality parts from reputable manufacturers.
• Proper Installation: Ensure that all components are installed correctly and securely.

Frequently Asked Questions

• What does the P1356 code mean? It means the PCM detected an unexpected high voltage or pulse from the ignition control circuit for cylinder 6 when it should be grounded.

• Can I drive my car with a P1356 code? It's not recommended, as it can cause misfires, damage to the catalytic converter, and reduced engine performance.

• Is the P1356 code difficult to fix? The difficulty depends on the root cause, ranging from simple wiring repairs to PCM replacement.

• Will replacing the ignition coil always fix the P1356 code? Not always; it's a common cause, but other factors like wiring, grounding, or PCM issues can also trigger the code. Proper diagnosis is essential.

• Can a bad spark plug cause a P1356 code? While a bad spark plug can cause a misfire, it typically wouldn't directly trigger P1356. P1356 specifically points to an issue with the IC output signal when the cylinder is grounded, indicating a problem with the ignition control circuit itself, rather than the spark plug.

Conclusion

The P1356 code indicates a problem with the ignition control circuit for cylinder 6, likely involving the ignition coil, wiring, or PCM. Thorough diagnosis and repair are necessary to restore engine performance and prevent further damage to the vehicle. Addressing this issue promptly will prevent more serious problems.