ICB - Flashing Code 2

Article ID: 448
Last updated: 07 Mar, 2023

Trane Package Unit: YCH

Re: Heating - Code 2

Code 2 = Failed to Sense or Sustain Flame (3 tries)

Qty Possible Causes:
2 Bad Glow Plug
Bad Ignition Control Board (ICB)
Bad Gas Valve
No Gas
Busted Burner


1. Prepare for Testing

  • Open the gas section access panel.
  • Place an amp probe on one wire going to the glow plug.

2. Check Inducer Motor

  • Reset the Ignition Control Board by momentarily unplugging the molex plug from the ICB.
  • The light on the ICB should flash continuous if a call for heat is present.
    • Light On (not flashing) = No call for heat ⇒ Energize a call for heat from the thermostat.
  • Ensure that the inducer motor starts normally.
    • No Inducer Operation ⇒ Check for 230V

3. Check the Glow Plug

  • Monitor the glow plug amperage as the unit goes through an ignition sequence.
  • Should draw approx. 3 Amps.
    • Low Amperage = Bad Glow Plug
    • No Amperage ⇒ Remove the plug feeding power to the glow plug and check for 120VAC between the two wires from the ICB during an ignition attempt.
      • No Voltage = Bad Ignition Control Board
      • Voltage + No Amperage = Bad Glow Plug 

4. Check Gas Pressure/Gas Valve

  • Manifold (Outlet) Pressure
    • A pressure gauge that reads negative pressure is required.
    • Proper manifold gas pressure = (-0.20" w.c.).
  • Monitor the gas pressure as the unit goes through an ignition sequence.
  • Pressure should start-off high negative and drop to -0.20" when the gas valve opens.
    • Pressure Drops to -0.20" but Does Not Ignite = Bad Burner
    • Pressure Doesn't Drop = Bad Gas Valve or No Inlet Gas ⇒ Check the inlet gas pressure.
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Article ID: 448
Last updated: 07 Mar, 2023
Revision: 6
Views: 42
Comments: 0