Message Name:

PIT SIGNAL STUCK ON

Message Code:

B3-006711

Associated CAS:

FIRE SYS FAULT
(Advisory)

The Pilot Initiated Test signal from PIT switch is asserted continuously for greater than 45 seconds.

• Fire-Detection-and-Extinguishing (FIREX) Control-Unit (A91)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Assure that the test switch has not been pressed for more than 45 seconds.
2. Verify the wiring from the press to test switch to the FIREX Control Unit (A91), plug A91P2, pin 34 should provide a ground when the press to test switch is pressed. Should be less than 1Ω.
3. If resistance is higher than normal, suspect the S101 test reset switch, ground GS2442 (other components should be failed), or the wiring between the switch and FIREX control unit.
4. If the wiring checks good, verify that the DCU is also receiving the press to test switch input. When the switch is pressed, A14EP1 should also receive a ground on pin 15H. Should be less than 1Ω. If the DCU is not receiving the ground, verify the wiring between the switch, ground GS2442, or S101 test reset switch.
5. If the above discrete wiring checks good, swap out or replace the FIREX Control Unit.