P0351 — Ignition Coil A Primary Control Circuit
P0351 sets when the ECM detects an open, short, or performance problem in the primary control circuit for ignition coil A (usually cylinder 1). Swap the coil with another cylinder — if the code moves, the coil is bad. Check for oil in the plug well that can damage the coil. Some coils fail intermittently when hot — test under operating temperature.
Fault Overview
Failed ignition coil, open or shorted control wire, poor coil ground, connector issues, and PCM driver fault (less common) are the primary causes.
Engine & Platform Coverage
Symptoms
- •P0351
- •ignition coil A circuit
- •coil primary circuit
- •P0351 cylinder 1 coil
- •ignition coil code
Possible Causes
- 1.Failed ignition coil
- 2.Open or shorted control wire
- 3.Poor coil ground
- 4.Connector issues
- 5.PCM driver fault (less common)
Wiring & Circuit Notes
Coil connector, control wire from PCM, power feed, and ground. Check for oil or corrosion in the connector.
DVOM Specs & Sensor Tests
Coil primary resistance. Control circuit voltage and current during cranking/running. Power and ground at the coil.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Step 1 — Confirm the Code Is for Coil A / Cylinder 1: Confirm the code is for coil A / cylinder 1 and check misfire counts on that cylinder.
- 2Step 2 — Swap the Coil with Another Cylinder: Swap the coil with another cylinder and retest. If the code or misfire follows the coil, replace it.
- 3Step 3 — Measure Primary Resistance and Control Circuit: Measure coil primary resistance and control circuit voltage and current.
- 4Step 4 — Check Power and Ground at the Coil: Check power and ground at the coil connector.
- 5Step 5 — Inspect Wiring and Connector: Inspect wiring and connector for oil intrusion, corrosion, or damage.
- 6Step 6 — Replace the Coil if It Fails the Swap Test: Replace the coil if it fails the swap test and the circuit is proven good.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Replace ignition coil $40–200; repair wiring or connector $50–200; repair oil leak into plug well $100–400.
Related Codes & Pages
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Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.