FixItFor.Us
P codepowertrainHigh severity

P0350Ignition Coil Primary/Secondary Circuit Malfunction

The PCM has detected an electrical fault in an ignition coil primary or secondary circuit without identifying which coil.

Definition

On coil-on-plug and coil-pack systems the PCM drives each coil's primary winding through a control circuit and monitors that circuit (and on many systems an ionization or feedback signal) for correct current flow and switching; P0350 sets when it detects an open, short, or missing feedback on a coil circuit it cannot attribute to a specific coil, often alongside a numbered coil code. Expect misfiring, rough idle, hesitation, and a MIL that may flash under load; sustained misfire dumps raw fuel into the exhaust and can overheat and destroy the catalytic converter, so the fault should not be driven on any longer than necessary.

Common causes

  • Failed ignition coil (shorted or open primary winding)
  • Damaged wiring or corroded connector in the coil power or control circuits
  • Open ignition feed to the coils (blown fuse, failed relay)
  • Poor coil ground or engine ground strap
  • Water intrusion into coil connectors or plug wells
  • PCM coil driver failure (rare, sometimes caused by a shorted coil)

Common misdiagnoses

  • Replacing all coils when a shared feed or ground is at fault
  • Replacing spark plugs alone for what is a circuit fault
  • Replacing the PCM without checking whether a shorted coil damaged the driver
  • Replacing the crank sensor for the misfire symptom

Troubleshooting steps

  1. 1.Check for accompanying coil-specific and misfire codes

    Codes P0351-P0358 or P030x misfire codes stored with P0350 identify which cylinder's circuit to start with.

  2. 2.Verify coil power supply

    Key on, confirm battery voltage on the coil feed wire at each connector and check the ignition fuse and relay; a dead shared feed sets circuit codes on multiple coils.

  3. 3.Test the control circuit

    Use a scope or noid-type test light on the coil trigger wire while cranking and confirm the PCM is switching the primary; a good trigger with no spark condemns the coil.

  4. 4.Measure coil primary resistance

    Compare primary winding resistance to spec (typically 0.4-2 Ω); an open or near-zero reading condemns the coil.

  5. 5.Inspect connectors and grounds

    Look for corrosion, bent pins, oil or water in plug wells, and verify the coil mounting/ground path is clean and tight.

  6. 6.Clear codes and confirm under load

    Verify smooth operation and no misfire counts on a road test that includes acceleration under load.

Related codes