Loss of Weight on Wheels Signal on the System 1

TASK 73-25-00-810-916-A
Loss of Weight on Wheels Signal on the System 1

1. Possible Causes

P0 port
PS12 sense line
LGCIU
EIU-1 [1KS1]
ECU [4000KS]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 72-23-00-000-006	Removal of the PS12 Line
AMM 72-23-00-000-040	Removal of the PS12 Line
AMM 72-23-00-280-002	Inspection/Check of the PS12 line
AMM 72-23-00-280-003	Inspection/Check of the PS12 Line
AMM 72-23-00-400-006	Installation of the PS12 Line
AMM 72-23-00-400-040	Installation of the PS12 Line
AMM 73-20-00-00-
AMM 73-21-60-000-001	Removal of the Electronic Control Unit (ECU)
AMM 73-21-60-400-001	Installation of the Electronic Control Unit (ECU)
AMM 73-25-34-000-040	Removal of the Engine Interface Unit (EIU)
AMM 73-25-34-400-040	Installation of the Engine Interface Unit (EIU)

3. Fault Confirmation
Subtask 73-25-00-710-280-A ** ON A/C NOT FOR ALL

A. Not applicable.

4. Fault Isolation
Subtask 73-25-00-810-168-B ** ON A/C NOT FOR ALL

A. Read the scheduled maintenance report or class 3 report and check if the maintenance message P0/P12/T12, ADC, ECU is present.
(1) If the message is present:

check the P0 port of the ECU for absence of blockage AMM 73-20-00-00-.
check the PS12 sense line for absence of blockage or leaks AMM 72-23-00-280-002. If leaks or blockage are found tighten unions or replace the PS12 sense line AMM 72-23-00-000-040 and AMM 72-23-00-400-040.

(2) If nothing is found:

Do a check of the Post Flight Report (PFR), of the Scheduled Maintenance Report (SMR) or class 3 Report and of the FADEC Last Leg Report for LGCIU failure.

(a) If message is present:

do the related trouble shooting procedure for the LGCIU .

(b) If no message is present:

replace the EIU-1 [1KS1] AMM 73-25-34-000-040 and AMM 73-25-34-400-040.

(3) If the fault repeats on the subsequent flights:

replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

Subtask 73-25-00-810-168-C ** ON A/C NOT FOR ALL

A. Read the scheduled maintenance report or class 3 report and check if the maintenance message P0/P12/T12, ADC, ECU is present.
(1) If the message is present:

check the P0 port of the ECU for absence of blockage AMM 73-20-00-00-.
check the PS12 sense line for absence of blockage or leaks AMM 72-23-00-280-003. If leaks or blockage are found tighten unions or replace the PS12 sense line AMM 72-23-00-000-006 and AMM 72-23-00-400-006.

(2) If nothing is found:

Do a check of the Post Flight Report (PFR), of the Scheduled Maintenance Report (SMR) or class 3 Report and of the FADEC Last Leg Report for LGCIU failure.

(a) If message is present:

do the related trouble shooting procedure for the LGCIU

(b) If no message is present:

replace the EIU-1 [1KS1] AMM 73-25-34-000-040 and AMM 73-25-34-400-040.

(3) If the fault repeats on the subsequent flights:

replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

[Rev.8 from Aug 2018] 2026.04.04 04:35:48 UTC