10V Pressure Reference not Correct (131-9(A))

TASK 49-00-81-810-899-A
10V Pressure Reference not Correct (131-9(A))

1. Possible Causes

PRESS XDCR WIRING SHOWS OPEN CIRCUIT
APU INLET PRESSURE TRANSDUCER (P22)
TOTAL PRESSURE TRANSDUCER (P23)
DELTA PRESSURE TRANSDUCER (P24)
APU [4005KM]
aircraft wiring
APU INLET PRESSURE TRANSDUCER (8048KM)
TOTAL PRESSURE TRANSDUCER (8044KM)
DELTA PRESSURE TRANSDUCER (8043KM)

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	MULTIMETER - STANDARD

B. Referenced Information

REFERENCE	DESIGNATION
AMM 49-11-11-000-004	Removal of the Power Plant (APU) (131-9(A))
AMM 49-11-11-400-004	Installation of the Power Plant (APU) (131-9(A))
AMM 49-51-16-000-002	Removal of the Transducer - Differential Pressure (131-9(A))
AMM 49-51-16-400-002	Installation of the Transducer - Differential Pressure (131-9(A))
AMM 49-51-17-000-002	Removal of the Transducer - Total Pressure (131-9(A))
AMM 49-51-17-400-002	Installation of the Transducer - Total Pressure (131-9(A))
AMM 49-51-21-000-001	Removal of the Transducer - APU Inlet Pressure (131-9(A))
AMM 49-51-21-400-001	Installation of the Transducer - APU Inlet Pressure (131-9(A))
ASM 496104

3. Fault Confirmation
Subtask 49-00-81-710-248-A ** ON A/C NOT FOR ALL

A. Read-out of ECB Trouble-Shooting Data
(1) Put the APU MASTER SW to the ON position.
(2) Get access to the APU LAST LEG/PREVIOUS LEG report.
(3) Push the '>' adjacent to the related CFDS failure message:

the MCDU menu shows
PRESS XDCR WIRING SHOWS OPEN CIRCUIT

(4) Get access to the APU GND SCANNING menu.

4. Fault Isolation
Subtask 49-00-81-810-164-A ** ON A/C NOT FOR ALL

A. If the APU GND SCANNING menu gives the maintenance message:

CHECK PRESSURE XDCR WIRING

associated with Fault Code Number (FCN) 30

disconnect the electrical connector P2 at the APU firewall.
Use a MULTIMETER - STANDARD to do a resistance check across pin 20 and pin 21 of the electrical connector P2.

(1) If the resistance is < 75 Ohms:

disconnect the electrical connector P22 of the APU INLET PRESSURE TRANSDUCER (P22).
Do a resistance check across pin 20 and pin 21 of the electrical connector P2 again.

(a) If the resistance is < 75 ohms:

replace the APU INLET PRESSURE TRANSDUCER (P22) AMM 49-51-21-000-001 and AMM 49-51-21-400-001.

(b) If the resistance is > 75 Ohms:

disconnect the electrical connector P23 of the TOTAL PRESSURE TRANSDUCER (P23).
Do a resistance check across pin 20 and pin 21 of the electrical connector P2 again.

1 If the resistance is < 75 Ohms:

replace the TOTAL PRESSURE TRANSDUCER (P23) AMM 49-51-17-000-002 and AMM 49-51-17-400-002.

2 If the resistance is > 75 Ohms:

disconnect the electrical connector P24 of the DELTA PRESSURE TRANSDUCER (P24).
Do a resistance check across pin 20 and pin 21 of the electrical connector P2 again.

a If the resistance is < 75 Ohms:

replace the DELTA PRESSURE TRANSDUCER (P24) AMM 49-51-16-000-002 and AMM 49-51-16-400-002.

b If the resistance is > 75 Ohms:

replace the APU [4005KM] AMM 49-11-11-000-004 and AMM 49-11-11-400-004.

(2) If the resistance is > 75 Ohms:

do a check and repair of the aircraft wiring between ECB (59KD) AB/A1,A4 and electrical connector P2/20,21 ASM 496104.

Subtask 49-00-81-810-164-B ** ON A/C NOT FOR ALL

A. If the APU GND SCANNING menu gives the maintenance message:

CHECK PRESSURE XDCR WIRING (8001KM)

associated with Fault Code Number (FCN) 30

disconnect the electrical connector P2 at the APU firewall.
Use a MULTIMETER - STANDARD to do a resistance check across pin 20 and pin 21 of the electrical connector P2.