🚨 Diagnostic Profile
Vehicle Make: Buick
Technical Description: IC Output High/Pulse Detected When Grounded Cyl. 7
This fault indicates that the Engine Control Module (ECM) has detected an abnormal voltage condition on the Ignition Control (IC) circuit for Cylinder 7. Specifically, when the module commands the coil driver to ground (turn on) for the dwell cycle, the feedback signal remains high or shows unexpected pulsing instead of dropping to the expected low reference voltage. This typically points to an open circuit, a shorted coil driver transistor, a damaged ignition coil, or a wiring fault between the ECM and the Cylinder 7 ignition coil.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires a digital multimeter and a capable scan tool with live ignition control (IC) waveform or bi-directional control capability. While no advanced module programming is typically required, proper diagnosis demands an understanding of ignition coil driver circuits, waveform analysis (ideally with a lab scope), and safe high-voltage ignition system handling. This is not a simple bolt-on part swap — root cause verification is essential before replacing components.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the Cylinder 7 ignition coil, its electrical connector, and the associated wiring harness. Look for:
– Corrosion, melted insulation, or chafed wires near the coil connector
– Signs of oil or coolant contamination at the coil boot
– Loose or corroded ECM harness connector pins
– Any aftermarket wiring splices or previous repair work in that circuit
Confirm the ignition coil itself is securely seated in the spark plug well and that the mounting bolt is properly torqued, as a poor ground connection can mimic this fault.
Step 2: Diagnostic Verification
Using a scan tool, access live data and monitor the IC (Ignition Control) circuit status for Cylinder 7 while cranking or running the engine (if it starts). Look specifically for:
– Commanded dwell time vs. actual feedback signal
– Any misfire counter increments on Cylinder 7
– Freeze frame data captured at the time the code set
Next, back-probe the ignition coil connector with a multimeter in DC volts mode. With the key on, engine off, verify reference voltage (typically 5V or 12V depending on platform) is present on the signal wire. Then, with a test light or by commanding the coil via bi-directional control, verify the ECM can pull the circuit to ground. If the circuit fails to ground properly, perform a continuity and resistance check between the ECM connector and coil connector to rule out an open or shorted wire. If wiring tests pass, the fault lies within the ignition coil driver itself or the ECM internal driver circuit.
Step 3: Resolution & Reset Process
If the ignition coil tests out of specification (shorted primary/secondary windings) or the circuit shows an open/short in the wiring harness, replace the affected ignition coil and/or repair the wiring harness using proper soldering and heat-shrink techniques (avoid crimp-only butt connectors in ignition circuits).
After the repair, clear the Diagnostic Trouble Codes (DTCs) using the scan tool. Perform a full drive cycle or use the scan tool’s built-in monitor reset function to confirm the IC circuit test passes and the code does not return. If the issue persists after coil and wiring repair, the ECM’s internal ignition driver module may be at fault, which would require ECM replacement and subsequent programming.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Ignition Coil (Cylinder 7), Coil-to-ECM Wiring Harness Repair Kit, Scan Tool with Bi-Directional Control, Digital Multimeter/Lab Scope, (Possible) ECM Replacement + Programming Software
Average Component Price: Ignition Coil: $45–$120 | Wiring Harness Repair: $30–$80 (parts only) | ECM (if required): $450–$900 + $150–$300 dealer programming fee
Estimated Labor Hours: Diagnosis: 0.5–1.0 hour | Coil Replacement: 0.3–0.5 hour | Wiring Harness Repair: 1.0–2.0 hours | ECM Replacement & Programming (if needed): 1.5–2.5 hours