P030C — Ignition A Control Signal Circuit High

Diagnostic algorithm

1. Step 1 — Verify: Read and record all DTCs and freeze-frame data. Note conditions (rpm, load, temp) when fault set. Clear codes and attempt to reproduce.
2. Step 2 — Visual Inspection: With ignition off, inspect the Ignition A wiring, connectors, and coil/module for damage, corrosion, oil or loose pins. Check relevant fuses and relays.
3. Step 3 — Power/Ground Checks: Verify battery voltage at coil/module power pin and confirm solid engine/PCM grounds. Repair any poor grounds or power feed issues.
4. Step 4 — Backprobe & Measure: Backprobe the Ignition A control pin at the coil/module while cranking or running. Use a DMM to check DC levels; use an oscilloscope to verify switching waveform. If signal is steadystate high, suspect short to battery or open driver.
5. Step 5 — Isolate Load: Disconnect coil/module connector and measure voltage at the PCM control pin. If the pin still reads high with the coil disconnected, wiring short or PCM fault likely. If it changes, fault may be in coil/module.
6. Step 6 — Component Swap/Test: If practical, swap the suspect coil/module with a known good one or bench-test the coil to confirm behavior. Re-scan for codes after swap.
7. Step 7 — Wiring Continuity: With battery disconnected, check continuity between coil connector and PCM pin; check for shorts to battery and to ground. Repair or replace damaged wiring/harness.
8. Step 8 — PCM/Driver Test: If wiring and coils are confirmed good and problem persists, test PCM driver outputs per manufacturer procedure or consult repair manual. Replace PCM only after confirming external circuit integrity.
9. Step 9 — Final Verification: After repairs, clear codes and road test under the conditions that previously set the code. Confirm the MIL remains off and misfire is resolved.