P1321 — Electronic Ignition System Fault Line

Causes

• Defective ignition coil or coil pack
• Faulty ignition control module or ignition driver in the PCM
• Damaged or corroded wiring/connectors in ignition circuit
• Open or shorted reference or ground circuit
• Faulty crankshaft or camshaft position sensor (timing/sync issue)
• Low battery voltage or poor battery/charging system condition

Symptoms

• Malfunction Indicator Lamp (MIL) illuminated
• Engine misfire or rough idle
• Hard starting or no-start condition
• Reduced engine power or hesitation under load
• Intermittent stalling or poor drivability

What to check

• Read and record freeze-frame data and stored misfire/related codes
• Visually inspect ignition coils, module, spark plugs and wiring for damage or corrosion
• Check battery voltage and charging system; ensure stable supply during cranking
• Verify power and ground at coils and ignition module connectors
• Inspect harness for chafing, melted insulation, or rodent damage near engine and firewall
• Check connectors for corrosion, bent pins, or poor contact

Signal parameters

• Crank/Cam sensor: digital trigger pulses synchronized to engine speed (expected coherent pulse train with engine cranking/running)
• Ignition coil primary: switched supply ~battery voltage (0–12V) with pulsed ground control when firing
• Ignition driver/control: PWM or pulsed trigger from PCM; pulses should align with cam/crank signals and RPM
• Reference circuits: typical sensor reference ~5V (verify stable reference with key on)
• No-load coil secondary: high-voltage pulse delivered to spark plug when commanded (verify with scope or appropriate HV probe)

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