🚨 Diagnostic Profile
Vehicle Make: Buick
Code/Condition: IC Output High/Pulse Detected When Grounded Cyl.3
This diagnostic condition relates to the Ignition Control (IC) circuit for Cylinder 3, monitored by the Powertrain Control Module (PCM). The PCM expects a specific voltage/pulse signal pattern from the ignition module during the IC circuit test. When the Cylinder 3 IC output wire is manually grounded during diagnostic testing, the PCM detects an unexpected high signal or pulse rather than the anticipated low/ground state. This typically points to a fault within the ignition control module driver circuit, a wiring short to voltage, or an internal PCM driver issue tied to the Cylinder 3 ignition coil/module pair.
🚨 Repair Difficulty Tier
[Intermediate]
This repair requires a digital multimeter, a scan tool capable of reading live ignition control data, and a solid understanding of distributorless ignition system (DIS) wiring. While no specialized module flashing or airbag-level safety liability is involved, misdiagnosis can lead to unnecessary ignition module or PCM replacement. Comfortable DIY mechanics with wiring diagram experience can attempt this, but most shops will classify it as an intermediate-level electrical diagnostic.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the ignition control wiring harness near Cylinder 3, checking for chafed insulation, corrosion at connector pins, or signs of melted/burnt wiring near the ignition module. Inspect the Cylinder 3 coil and module connector for secure seating and confirm there is no bare wire shorting to a 12V source or ground. Check for aftermarket wiring modifications or previous repair splices in this circuit.
Step 2: Diagnostic Verification
Using a scan tool, access PCM live data and monitor the IC (Ignition Control) signal status for Cylinder 3 while cranking or running the engine. Back-probe the Cylinder 3 IC signal wire at the PCM connector with a multimeter set to DC volts; a healthy circuit should toggle between near 0V and 5V in sync with ignition pulses. If the voltage remains high (close to 12V or system voltage) even when the circuit is grounded during the test procedure, this confirms a short-to-voltage condition or a failed ignition module driver transistor. Cross-reference readings against Cylinder 1 and 2 circuits for comparison, as healthy cylinders will show normal low-to-high toggling.
Step 3: Resolution & Reset Process
If testing confirms a wiring short to voltage, repair or replace the damaged harness section with OEM-spec wiring and re-insulate connections. If the ignition module driver for Cylinder 3 is confirmed faulty (output remains high regardless of PCM command), replace the ignition control module assembly. In rare cases where the module tests good but the fault persists, inspect the PCM driver circuit itself, as an internal PCM fault may require PCM replacement and re-flashing with updated calibration software. After repairs, clear PCM diagnostic trouble codes and perform a drive cycle while monitoring IC circuit live data to confirm normal pulse behavior and no code recurrence.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Ignition Control Module, Cylinder 3 Coil Pack (if integrated), wiring harness repair kit/connector pigtail, PCM reflash software (dealer-level, if PCM fault confirmed), digital multimeter, and OEM scan tool or equivalent aftermarket scanner with live ignition data capability.
Average Component Price: Ignition Control Module: $85–$220 | Coil Pack (if separate): $45–$130 | Wiring Harness Repair Kit: $25–$60 | PCM (if required): $350–$650 plus $120–$250 for dealer programming.
Estimated Labor Hours: Diagnostic testing: 0.8–1.5 hours | Ignition module/coil replacement: 0.5–1.0 hour | Wiring harness repair: 1.0–2.0 hours | PCM replacement and programming (if needed): 1.5–2.5 hours.