🚨 Diagnostic Profile
Vehicle/Equipment Make: Buick
Technical Description: IC Output High/Pulse Detected When Grounded Cyl.2
This diagnostic condition is associated with the Ignition Control (IC) circuit between the Powertrain Control Module (PCM) and the ignition module or coil driver circuit for Cylinder 2. The PCM expects to see a specific voltage pulse pattern on the IC circuit when it commands the ignition module to fire. When this circuit is grounded or shorted, the PCM detects an abnormally high signal or an unexpected pulse pattern, indicating a fault in the IC control wiring, the ignition module, or the PCM driver itself.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires the use of a bidirectional scan tool capable of reading ignition system live data, as well as a digital multimeter or oscilloscope to properly test the IC circuit waveform. While no airbag or restraint systems are involved, accurate diagnosis requires knowledge of ignition module operation, PCM driver circuits, and proper wiring diagram interpretation. This is not a simple bolt-on part replacement and may require circuit-level testing before condemning a component.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness between the PCM and the ignition control module, paying close attention to the Cylinder 2 IC circuit wire. Look for signs of chafing, melted insulation, corrosion at connector pins, or any area where the wire may have been pinched against the engine block or chassis, which could cause an intermittent or constant short to ground. Also inspect the ignition module and coil assembly for cracks, carbon tracking, or moisture intrusion that could create an unintended ground path.
Step 2: Diagnostic Verification
Connect a scan tool and monitor live ignition control data, if available, to check for IC circuit status flags or misfire counters on Cylinder 2. Using a digital multimeter, back-probe the IC signal wire at the PCM connector with the key on, engine off, and verify there is no continuity to ground (resistance should read as open or very high, not near 0 ohms). If a short to ground is confirmed, isolate the circuit by disconnecting the ignition module connector and retesting the wire alone to determine whether the fault lies in the harness or inside the module itself. For more precise results, use an oscilloscope to capture the IC waveform during cranking and compare it to known-good pulse patterns for that ignition system.
Step 3: Resolution & Reset Process
If the wiring harness is found to be shorted to ground, repair or replace the damaged section of wire using proper soldering and heat-shrink techniques, ensuring the repair is routed away from heat sources and moving parts. If the ignition module or coil assembly is found to be internally shorted, replace the faulty component with an OEM or OEM-equivalent part. After repairs are complete, clear the diagnostic trouble codes using the scan tool, then perform several drive cycles while monitoring live data to confirm the IC circuit reads normally with no recurring faults. Finally, verify there are no misfire codes present on Cylinder 2 during idle and under load conditions.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Ignition control module, Cylinder 2 ignition coil (if integrated or suspect), wiring harness repair kit (connectors, terminals, wire loom), bidirectional scan tool, digital multimeter or oscilloscope.
Average Component Price: $45 – $180 for an ignition coil or module (depending on type: coil-on-plug vs. distributor-style ignition module), $15 – $40 for wiring repair materials. No special dealer software flashing is typically required for this repair.
Estimated Labor Hours: 1.0 – 2.5 hours for diagnosis and circuit testing, plus an additional 0.5 – 1.5 hours for component replacement or wiring repair, depending on accessibility of the ignition module and harness routing.