DOC AIRBUS | TSM A320FLoss of Fuel Control on the Engine 2, Channel A
1. Possible Causes
NOTE: This task is to troubleshoot the Clear Language Message (CLM) CHA FMU/HC/EEC2 The fault acronyms
listed in the fault confirmation section below will help you focus on the correct cause of this CLM.
· FMU ( 4000KC )
· EEC ( 4000KS )
2 Job Set-up Information
A. Referenced Information
REFERENCE DESIGNATION
73-00-00-810-900-B Multiple Dual Track Check Faults on the Engine 1
Ref. AMM 24-41-00-861-002 Energize the Aircraft Electrical Circuits from the External Power
Ref. AMM 24-41-00-862-002 De-energize the Aircraft Electrical Circuits Supplied from the External
Power
Ref. AMM 31-60-00-860-002 EIS Stop Procedure
Ref. AMM 70-23-15-912-010 Connection of Electrical Connectors
Ref. AMM 71-00-00-710-013 Test No.11 : High Power Assurance Test
Ref. AMM 71-13-00-010-010 Opening of the Fan Cowls 437AL(447AL),438AR(448AR)
Ref. AMM 71-50-00-210-010 Wire Harness Visual Inspection - All Power Plant Electrical Cables
Ref. AMM 73-22-00-710-040 Operational Test of the FADEC SYSTEM on the Ground
Ref. AMM 73-22-34-000-010 Removal of the Electronic Engine Control (EEC)
Ref. AMM 73-22-34-400-010 Installation of the Electronic Engine Control (EEC)
Ref. AMM 73-22-52-000-010 Removal of the Fuel Metering Unit (FMU)
Ref. AMM 73-22-52-400-010 Installation of the Fuel Metering Unit (FMU)
Ref. ASM 73-25-18
Ref. AMM 78-32-00-010-010 Opening of the Thrust Reverser Halves
70-00-00-03-13 STANDARD PRACTICES - ENGINE - GENERAL - TASK SUPPORTING
DATA
Fuel Control SHEET 1
Figure 73(IAE)-00-00-991-00800-B / SHEET 1/1 - Fuel Control not printed, as per printing preferences
3. Fault Confirmation
Subtask 73-00-00-860-178-A
A. Job Set-up
(1) Energize the aircraft electrical circuits
Ref. AMM 24-41-00-861-002 .
(2) On the overhead panel 50VU, set the ENG FADEC GND PWR 2 pushbutton switch to the ON
position.
Subtask 73-00-00-710-340-A
B. Identify test to make sure that the fault is present
NOTE: Troubleshooting can start immediately without doing the fault confirmation if this CLM was indicated
in multiple flight or ground legs.
(1) Do the CFDS message decoding to identify the fault acronym related to the CLM message
(Ref. TSM 70-00-00-03) .
(2) If the readout gives the fault acronym WFWAF in FADEC 2A, do the FADEC system operational test
for fault confirmation Ref. AMM 73-22-00-710-040 .
(a) If test gives the fault acronym WFWAF in FADEC 2A, or there are two or more occurrences in the
fault history, continue with fault isolation Para. 4.A.
(b) If test does not give the fault acronym WFWAF, and there is no history of faults, return the engine
to service.
(3) If the readout gives the fault acronym WFL in FADEC 2A, do the FADEC system operational test for
fault confirmation Ref. AMM 73-22-00-710-040 .
(a) If test gives the fault acronym WFL in FADEC 2A, or there are two or more occurrences in the
fault history, continue with fault isolation Para. 4.B.
(b) If the test does not give the fault acronym WFL, and there is no history of faults, return the engine
to service.
(4) If the readout gives the fault acronym WFTK in FADEC 2A, do a high power assurance test for the
fault confirmation as follows:
(a) On the overhead panel 50VU, set the ENG FADEC GND PWR 2 pushbutton to the ON position.
NOTE: This action resets the FADEC memory.
(b) Do the test No. 11: high power assurance test Ref. AMM 71-00-00-710-013 .
(c) Read the LAST LEG REPORT of the FADEC (2A) menu on the MCDU (Ref. TSM 70-00-00-03) :
1 Make a record of the failure message.
2 Make a record of the channel FADEC 2A which found the fault.
3 Do the CFDS message decoding to identify the fault acronym.
NOTE: Multiple dual track check faults may indicate a failed fuel pump. Four control units
on the engine are driven by HP fuel: the VSV actuator, the 2.5 bleed controller, the
ACOC air modulating valve and the active clearance control actuator. If you have
faults with two or more of these units, you must follow the multiple dual track check
faults procedure (Ref. TSM 73-00-00-810-900) .
(d) If the test gives the fault acronym WFTK or there are two or more occurrences in the fault history,
continue with fault isolation Para 4.C.
(e) If the test does not give the fault acronym WFTK, and there is no history of faults, then return
engine to service.
4. Fault Isolation
(Ref. Fig. Fuel Control SHEET 1)
Subtask 73-00-00-810-178-A
A. Fault Isolation for fault acronym WFWAF
A torque motor Wrap Around Fault (WAF) was found in channel A. The circuit for the FMU metering valve
is open, short-to-ground, or has a wire-to-wire short.
NOTE: At any time during this procedure, you can do the steps in Para. 3 to make sure that the fault is
corrected.
NOTE: Removal and installation of the electrical connectors can correct this fault.
(1) Do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J3) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 .
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wiring chafing.
4 If a problem is found with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-B) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connector:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do this electrical check of the channel A torque motor circuit in the FMU metering valve Ref.
ASM 73-25-18.
1 Make sure that contacts G and F are not shorted to ground.
2 Make sure that contacts G and F are not shorted to other contacts in the connector.
3 Make sure that the resistance from contact G to contact F is between 68 and 110 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J3) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connector:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the torque motor wiring in the channel A harness. Look for:
1 Wire-to-wire shorts and shorts to ground.
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity.
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure the contacts are in the correct positions in each connector as specified in
the wiring diagram.
FMU Torque Motor Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
4000KC-B 4000KS-J3
Contacts Contacts
G K
F J
3 If a problem is found with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for this fault, listed in Para. 3 for fault confirmation.
1 If the test does not give the fault acronym WFWAF, return the engine to service.
2 If the test gives the fault acronym WFWAF, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If the fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
Subtask 73-00-00-810-224-A
B. Fault Isolation for the Fault Acronym WFL
The FMU resolver signal is out of range.This is caused by an open, short to ground, or a wire-to-wire short
in this circuit.
NOTE: At any time during this procedure, you can do the steps in Para. 3 to make sure that the fault is
corrected.
NOTE: Removal and installation of the electrical connectors can correct this fault.
(1) Do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J2) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 .
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wiring chafing.
4 If a problem is found with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-B) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connector:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel A resolver circuit in the FMU resolver Ref. ASM 73-25-18.
1 Make sure that contacts E, C, D, B and A are not shorted to ground.
2 Make sure that contacts E, C, D, B and A are not shorted to other contacts in the connector.
3 Make sure that the resistance from contact E to contact D is between 15 and 78 ohms.
4 Make sure that the resistance from contact C to contact D is between 15 and 78 ohms.
5 Make sure that the resistance from contact B to contact A is between 54 and 103 ohms.
6 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J2) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary
(e) Do the electrical check of the resolver harness in the channel A. Look for:
1 Wire-to-wire shortsand shorts to ground.
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity.
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
FMU Resolver Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
4000KC-B 4000KS-J2
Contacts Contacts
E V
C i
D j
B W
A A
3 If a problem is found with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for this fault, listed in Para. 3 for fault confirmation.
1 If the test does not give the fault acronym WFL, return the engine to service.
2 If the test gives the fault acronym WFL, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If the fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
Subtask 73-00-00-810-225-A
C. Fault Isolation for Fault Acronym WFTK
A Track-check fault was found in channel A. The FMU cannot move to its commanded position or it is
moving slower than normal.
NOTE: At any time during this procedure, you can do the steps in Para. 3 to make sure that the fault is
corrected.
NOTE: This fault is typically caused by a mechanical problem and not an electrical problem.
(1) Open the thrust reverser halves Ref. AMM 78-32-00-010-010 and and fan cowls as necessary Ref.
AMM 71-13-00-010-010 .
(2) Remove and replace the FMU ( 4000KC ) Ref. AMM 73-22-52-000-010 and Ref.
AMM 73-22-52-400-010 .
(3) Do the test listed in Para. 3 for fault confirmation.
(4) If the test was satisfactory, send the engine back to service.
(5) If the fault continues, remove and replace the EEC ( 4000KS ) Ref. AMM 73-22-34-000-010 and
Ref. AMM 73-22-34-400-010 .
(6) If the fault continues. Do the following:
(a) Do the steps for the fault acronym WFWAF listed in Para. 4.A above.
(b) Do the steps for the fault acronym WFL listed in Para. 4.B above.
5. Close-up
Subtask 73-00-00-860-179-A
A. Put the aircraft back to its initial configuration.
(1) Close the thrust reverser halves, activate the thrust reverser HCU, close the fan cowls and remove
the warning notices Ref. AMM 71-50-00-210-010 .
(2) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
Ref. AMM 31-60-00-860-002 .
(3) On the panel 50VU, push the ENG FADEC GND PWR 2 pushbutton switch.
(4) De-energize the aircraft electrical circuits
Ref. AMM 24-41-00-862-002 . [Rev.6 from Feb 2017] 2026.04.04 04:36:08 UTC