🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: IC Output High/Pulse Detected When Grounded Cyl.5
This diagnostic trouble code indicates that the Ignition Control (IC) module has detected an abnormal output signal on the Cylinder 5 ignition control circuit. Specifically, the Powertrain Control Module (PCM) expects a specific voltage transition pattern when the IC circuit is commanded to ground, but instead detects a high voltage or an unexpected pulse signature. This typically points to an issue within the ignition coil driver circuit, a short to voltage in the wiring harness, or an internal fault in the ignition module/coil pack assembly responsible for firing Cylinder 5.
🚨 Repair Difficulty Tier
Rating: [Intermediate]
This repair requires the use of a digital multimeter and a capable scan tool with live data streaming (bi-directional control preferred) to properly isolate whether the fault lies within the wiring harness, the ignition module, or the coil pack. While not as high-liability as airbag or restraint system work, this repair does require intermediate electrical diagnostic knowledge of ignition primary and secondary circuits, as well as careful component testing to avoid misdiagnosis and unnecessary parts replacement.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the ignition coil pack assembly and all connectors related to Cylinder 5. Check for melted, burnt, or corroded terminals at the IC module connector. Inspect the wiring harness for chafing, pinched wires, or exposed conductors that could be shorting to the vehicle chassis or to a voltage source. Confirm that the coil pack mounting is secure and that there is no visible carbon tracking on the coil boot or spark plug well for Cylinder 5.
Step 2: Diagnostic Verification
Connect a scan tool capable of reading live PCM data and monitor the IC signal output for Cylinder 5 while cranking or running the engine (if it starts). Compare the voltage pattern against known-good waveform specifications — a healthy circuit should toggle cleanly between low (grounded) and high states. Using a digital multimeter in DC voltage mode, backprobe the IC circuit wire at the PCM connector with the ignition on; a reading staying high (battery voltage) when it should pulse to ground confirms a short-to-voltage condition. Additionally, use an oscilloscope if available to check for noise or pulse irregularities indicating an internal coil driver fault.
Step 3: Resolution & Reset Process
If the wiring harness tests are normal but the coil pack fails the pulse test, replace the ignition coil pack assembly for Cylinder 5. If the harness is found to have a short to voltage, repair or replace the damaged wiring section and secure with appropriate harness loom and connectors. After repairs, clear the Diagnostic Trouble Codes (DTCs) using the scan tool, perform a PCM reset/relearn procedure if required by the vehicle’s service manual, and conduct a test drive while monitoring live data to confirm the IC output now pulses correctly to ground without triggering the fault code again.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Ignition Coil Pack (Cylinder 5), Ignition Control Module (if integrated separately), Wiring Harness Repair Kit/Connector Pigtail, OBD-II Scan Tool with Live Data/Bi-Directional Capability
Average Component Price: $45 – $180 (Coil Pack/Module); $15 – $50 (Harness Repair Kit)
Estimated Labor Hours: 1.0 – 2.5 hours (includes diagnostic time, component replacement, and PCM reset/verification)