🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: IC Output High/Pulse Detected When Grounded Cyl.6
This diagnostic trouble code indicates that the Ignition Control (IC) circuit for Cylinder 6 is reporting a high-voltage or pulse signal condition when the Powertrain Control Module (PCM) commands the circuit to ground. This typically points to an issue within the ignition control module, coil driver circuit, or a wiring fault between the PCM and the ignition coil/module for the affected cylinder. The IC circuit is used by the PCM to monitor spark timing feedback, and an abnormal signal suggests the coil driver transistor is not pulling the circuit to ground properly or there is a short/open in the control wire.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires the use of a professional-grade scan tool capable of reading live ignition control data, along with a digital multimeter or oscilloscope to test circuit continuity, voltage, and pulse patterns. While no airbag or restraint systems are involved, a solid understanding of ignition system electrical theory and PCM communication is necessary to accurately isolate the fault between the module, wiring harness, and ignition coil pack.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by performing a visual inspection of the ignition coil assembly, coil-on-plug connector for Cylinder 6, and the associated wiring harness. Look for signs of corrosion, melted insulation, loose connector pins, or chafed wires near the engine block or valve cover area. Check the ignition module (if equipped with a separate module) for cracks, carbon tracking, or heat damage. Inspect the PCM connector pins for the IC circuit to ensure no bent or corroded terminals are present, as this can cause an intermittent high-voltage reading.
Step 2: Diagnostic Verification
Connect a scan tool to the vehicle’s OBD-II port and access PCM live data streams, specifically monitoring the Ignition Control (IC) signal for Cylinder 6 during cranking and idle conditions. Compare the waveform pattern to a known-good cylinder to identify irregular pulse widths or voltage spikes. Next, backprobe the IC circuit wire at the coil connector using a multimeter or oscilloscope to verify the signal switches cleanly between 0V (grounded) and reference voltage (typically 5V) when the engine is cranked. A circuit that fails to pull low or shows erratic voltage spikes confirms a coil driver or wiring fault rather than a false PCM code.
Step 3: Resolution & Reset Process
If the wiring and connector are found to be in good condition, replace the ignition coil or ignition control module assigned to Cylinder 6, as the internal driver transistor is the most common point of failure. After replacement, clear the Diagnostic Trouble Codes using the scan tool and perform a key-cycle test to confirm the code does not reset. Finally, conduct a road test while monitoring live IC data to verify consistent pulse behavior across all cylinders and ensure no misfire codes are triggered under load.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Replacement ignition coil (coil-on-plug) for Cylinder 6, OEM wiring harness pigtail connector (if damaged), digital multimeter or oscilloscope, and a professional-grade bi-directional scan tool for live data monitoring and code clearing.
Average Component Price: $45 – $120 for an OEM or high-quality aftermarket ignition coil; $25 – $60 for a wiring harness connector repair kit if needed.
Estimated Labor Hours: 0.5 to 1.5 hours for diagnosis and coil replacement; add an additional 0.5 hours if harness repair or PCM connector cleaning is required.