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DTC codes / P03xx · Ignition system and misfire / P036C

P036CIgnition G Control Signal Circuit High

P036C indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the ignition control circuit for coil or cylinder 'G'. This circuit is responsible for triggering the ignition coil to fire the spark plug, and a high signal suggests a short to voltage, an open circuit, or a faulty coil driver.

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

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Engine misfire, rough idle, or hesitation during acceleration
  • Reduced engine power or limp mode in some vehicles
  • Poor fuel economy due to incomplete combustion
  • Difficulty starting or stalling, especially when the engine is cold
  • A noticeable vibration or shaking from the engine bay

Common causes, most likely first

  1. Faulty ignition coil or coil pack for cylinder 'G'
  2. Damaged or chafed wiring in the ignition control circuit (short to voltage)
  3. Corroded or loose electrical connector at the ignition coil or PCM
  4. Failed ignition control module (ICM) or driver circuit inside the PCM
  5. Open circuit in the ground path for the ignition coil
  6. Aftermarket alarm or remote start system interfering with ignition wiring

How to diagnose and fix it

  1. Perform a visual inspection of the ignition coil, wiring, and connectors for damage or corrosion
  2. Use a scan tool to check for other stored codes and freeze-frame data to confirm the fault conditions
  3. Test the ignition control circuit for a short to voltage using a digital multimeter (DMM) with the key on and engine off
  4. Check the resistance of the ignition coil primary and secondary windings against the manufacturer's specification
  5. Inspect and test the ground circuit for the ignition coil for continuity and resistance
  6. Swap the ignition coil from cylinder 'G' with a known-good coil from another cylinder to see if the code follows
  7. If all external components test good, diagnose the PCM driver circuit or replace the PCM as a last resort

High Voltage Signal Does Not Always Mean a Bad Coil

  • A short to voltage on the ignition control circuit often originates from a rubbed wire harness near hot exhaust components, not from the coil itself.
  • Some vehicles use a shared ignition control circuit for multiple cylinders, so a fault in one coil can affect others and set multiple codes.
  • A failed ignition coil driver inside the PCM can cause a high signal code, but this is rare and should only be suspected after all external wiring and components are ruled out.
  • Aftermarket electrical accessories tapped into the ignition circuit can introduce voltage spikes that trigger P036C without any hard failure.
  • The code may set intermittently due to a loose connector that only loses contact during engine vibration, so wiggle tests are essential during diagnosis.

Can I keep driving with P036C?

Driving with P036C is generally not recommended because the misfire can damage the catalytic converter and reduce engine performance. If the check engine light is flashing, stop driving immediately and seek professional repair; otherwise, drive cautiously to a repair shop and avoid heavy acceleration.

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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