Ignition

P036B — Ignition G Control Signal Circuit Low

Severity: medium Drive with care, to a shop

What P036B means

The engine control module fires the ignition coils using control signals and monitors their voltage. P036B sets when the signal in the ignition "G" control circuit is lower than expected, due to an open, a short to ground, or a failing coil or driver. Which cylinder circuit G refers to depends on the manufacturer and engine, so check the wiring diagram for your vehicle.

Symptoms

  • Check Engine light on
  • Hesitation or weak acceleration
  • Rough idle
  • Poor fuel economy
  • Possible misfires, with a flashing Check Engine light under load
  • Hard starting

Possible causes

  1. Open or short to ground in the ignition G control wire
  2. Faulty ignition coil or its built-in driver
  3. Corroded, loose or damaged connector pins
  4. Damaged wiring harness (chafing, heat damage, rodents)
  5. Camshaft position sensor or its circuit, if linked to this circuit on your engine
  6. Failed ECM (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and look for related misfire codes (P030x).
  2. Inspect the coil connector and harness for corrosion, melting, chafing or loose locks.
  3. Use the wiring diagram to find which coil circuit G feeds, then check power and ground at the connector.
  4. Swap the coil with one from another cylinder and see whether the fault follows it.
  5. Test the control wire from the coil connector to the ECM for opens and shorts to ground.
  6. Inspect the spark plugs and replace them if worn or damaged.
  7. Check the camshaft sensor circuit if the diagram shows a link.
  8. If wiring and coil are good, test the ECM driver and reflash or replace the unit if needed.

Common fixes

  • Repair the wiring or replace a damaged connector
  • Replace the faulty ignition coil
  • Replace worn spark plugs
  • Reprogram or replace the ECM if confirmed faulty

Questions and answers

What does P036B mean?

It means a low signal in the ignition G control circuit. The ECM is not seeing the expected voltage on that circuit, most often because of wiring, a connector or a coil.

Can I drive with P036B?

Briefly and carefully, until it is repaired. Misfires can harm the catalytic converter and raise fuel use, and if the Check Engine light flashes you should stop driving.

What most often causes P036B?

Most often it is damaged wiring or a poor connection at the coil connector, followed by the coil itself. A failed ECM is rare.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.