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DTC codes / P03xx · Ignition system and misfire / P036A

P036AIgnition G Control Signal Circuit/Open

P036A indicates that the powertrain control module (PCM) has detected an open circuit or loss of signal on the ignition control circuit for ignition coil or spark plug 'G'. The PCM commands a dwell signal to fire the coil, but the feedback or voltage on the control wire does not match the expected profile, so the circuit is flagged as open.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Engine misfire or rough running, especially under load or at idle.
  • Reduced engine power or a limp-home mode in some vehicles.
  • Difficulty starting or a no-start condition if the affected cylinder is critical.
  • Slight decrease in fuel economy due to incomplete combustion.

Common causes, most likely first

  1. Broken, chafed, or corroded wire in the ignition coil 'G' control circuit.
  2. Loose or damaged electrical connector at the ignition coil or PCM.
  3. Failed ignition coil 'G' with an open internal primary winding.
  4. Faulty PCM driver for that specific ignition circuit (rare but possible).
  5. Water intrusion or corrosion in the coil-on-plug well or harness.
  6. Aftermarket alarm or remote start wiring that has compromised the ignition circuit.

How to diagnose and fix it

  1. Perform a visual inspection of the ignition coil 'G' connector and wiring for damage, corrosion, or loose pins.
  2. Use a scan tool to check for other misfire or ignition codes and confirm P036A is current.
  3. Measure resistance of the ignition coil 'G' primary winding and compare to specification.
  4. Back-probe the control circuit at the coil and check for a pulsed signal (dwell) while cranking or running.
  5. Check continuity and resistance of the control wire from the coil connector to the PCM connector.
  6. If the circuit tests good, swap the suspect coil with a known-good coil from another cylinder to see if the misfire moves.
  7. Repair or replace the faulty wiring, connector, or ignition coil as needed, then clear codes and verify the repair.

Ignition coil G circuit traps to avoid

  • A loose or corroded ground at the engine block can cause an open circuit code for an ignition coil even when the coil and wiring test fine.
  • Some vehicles use a shared power feed for multiple coils, so a blown fuse or relay can set a code for only one coil if the others are on a separate circuit.
  • The PCM may set P036A intermittently due to a poor connection that only acts up when the engine is hot or vibrating, so wiggle-testing the harness is essential.
  • Aftermarket spark plugs with incorrect resistance can stress the coil and eventually cause an open circuit code, so always verify plug specification.
  • Do not replace the PCM based solely on this code; the driver circuit is rarely the cause, and a noid light or oscilloscope test can confirm PCM function.

Can I keep driving with P036A?

If the check engine light is on but the engine runs smoothly, you can drive cautiously to a repair shop, but avoid heavy acceleration or towing. If the engine is misfiring, running rough, or lacks power, stop driving and have the vehicle towed to prevent catalytic converter damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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