🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: Ignition Control Circuit Group B
This diagnostic code refers to a malfunction within the secondary ignition control circuitry, typically associated with the Ignition Control Module (ICM) or Powertrain Control Module (PCM) communication with a specific bank or group of ignition coil drivers. A fault in Group B suggests the Engine Control Module is not receiving the correct reference signal voltage or feedback from a subset of the ignition coil pack, which can cause misfires, rough idle, or a no-start condition depending on severity.
🚨 Repair Difficulty Tier
Rating: Intermediate
This repair falls into the Intermediate category. While replacing the physical ignition coil or module itself requires only basic hand tools, accurately diagnosing which circuit (Group B specifically) is failing requires the use of a digital multimeter to check for resistance and voltage drop, as well as an OBD-II scanner capable of reading live ignition timing and misfire data. Attempting to replace parts without verifying the circuit with a meter first often results in misdiagnosis and unnecessary part replacement.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by performing a visual inspection of the wiring harness connected to the ignition coils associated with Group B (typically cylinders 2, 4, 6 or specific to GM coil pack mapping). Look for signs of melted plastic connectors, chafed wires, or corrosion at the pins. Inspect the ignition coil boots for cracking or carbon tracking, and check the spark plugs for fouling which could indicate a prolonged misfire in that specific group.
Step 2: Diagnostic Verification
Connect an OBD-II scan tool to view live data stream, specifically monitoring ‘Ignition Control Circuit’ voltage feedback for Group B while cranking or running the engine. Use a digital multimeter to back-probe the connector at the PCM or ICM; you should see a clean square wave or consistent reference voltage (usually 5v or 12v depending on the circuit design). A reading of 0 volts or an erratic signal confirms an open or shorted circuit rather than a dead component.
Step 3: Resolution & Reset Process
If the circuit tests open, repair or replace the damaged wiring harness section connecting to the Group B coils. If the wiring tests good but the coil fails to trigger, replace the specific ignition coil or the Ignition Control Module if integrated. After the physical repair, clear the Diagnostic Trouble Codes (DTCs) using the scan tool and perform a ‘Key Cycle’ test (ignition on/off 3 times) to confirm the PCM registers the circuit as repaired. Finally, perform a test drive to ensure no pending codes return.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: OBD-II Diagnostic Scanner, Digital Multimeter, Replacement Ignition Coil(s), Wiring Harness Pigtail Connectors (if applicable).
Average Component Price: $45 – $120 USD (per coil pack unit); Wiring harness repair kits typically range from $20 – $50 USD.
Estimated Labor Hours: 0.5 to 1.5 hours for standard diagnosis and coil replacement; up to 2.5 hours if deep wiring harness repair or ICM replacement is required.