Loss of the EGT Thermocouple Signal to the ECU on Engine 2

TASK 77-20-00-810-804-A
Loss of the EGT Thermocouple Signal to the ECU on Engine 2

1. Possible Causes

harness J13
ECU [4000KS]
harness CJ13
lower left-hand thermocouple lead assembly
lower right-hand thermocouple lead assembly
upper left-hand thermocouple lead assembly
three-probe thermocouple lead assembly
upper extension lead
lower extension lead
main junction box assembly
harness HJ13

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AWM 715109
AMM 73-21-50-000-005	Removal of the CJ13 Harness
AMM 73-21-50-000-012	Removal of the J13 Harness
AMM 73-21-50-000-029	Removal of the CJ13 Harness
AMM 73-21-50-000-046	Removal of the HJ13 Harness for SAC Engines
AMM 73-21-50-400-005	Installation of the CJ13 Harness
AMM 73-21-50-400-012	Installation of the J13 Harness
AMM 73-21-50-400-029	Installation of the CJ13 Harness
AMM 73-21-50-400-046	Installation of the HJ13 Harness for SAC Engines
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)
ASM 732515
AMM 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)
AMM 77-21-10-000-001	Removal of the Upper Extension Lead
AMM 77-21-10-000-002	Removal of the Main Junction Box
AMM 77-21-10-000-003	Removal of the Upper Right Thermocouple Lead Assembly
AMM 77-21-10-000-004	Removal of the Lower Left Thermocouple Lead Assembly
AMM 77-21-10-000-005	Removal of the Lower Right Thermocouple Lead Assembly
AMM 77-21-10-000-006	Removal of the Lower Extension Lead
AMM 77-21-10-000-007	Removal of the Upper Left Thermocouple Lead Assembly
AMM 77-21-10-000-008	Removal of the Upper Extension Lead
AMM 77-21-10-000-009	Removal of the Lower Extension Lead
AMM 77-21-10-000-025	Removal of the Main Junction Box
AMM 77-21-10-000-026	Removal of the Upper Right Thermocouple Lead Assembly
AMM 77-21-10-000-027	Removal of the Lower Left Thermocouple Lead Assembly
AMM 77-21-10-000-028	Removal of the Upper Left Thermocouple Lead Assembly
AMM 77-21-10-000-029	Removal of the Lower Right Thermocouple Lead Assembly
AMM 77-21-10-200-001	Inspection/Check of the T495 Thermocouple Wiring Harness
AMM 77-21-10-200-002	Inspection/Check of the T495 Thermocouple Wiring Harness
AMM 77-21-10-400-001	Installation of the Upper Extension Lead
AMM 77-21-10-400-002	Installation of the Main Junction Box
AMM 77-21-10-400-003	Installation of the Upper Right Thermocouple Lead Assembly
AMM 77-21-10-400-004	Installation of the Lower Left Thermocouple Lead Assembly
AMM 77-21-10-400-005	Installation of the Lower Right Thermocouple Lead Assembly
AMM 77-21-10-400-006	Installation of the Lower Extension Lead
AMM 77-21-10-400-007	Installation of the Upper Left Thermocouple Lead Assembly
AMM 77-21-10-400-008	Installation of the Upper Extension Lead
AMM 77-21-10-400-009	Installation of the Lower Extension Lead
AMM 77-21-10-400-025	Installation of the Main Junction Box
AMM 77-21-10-400-026	Installation of the Upper Right Thermocouple Lead Assembly
AMM 77-21-10-400-027	Installation of the Lower Left Thermocouple Lead Assembly
AMM 77-21-10-400-028	Installation of the Upper Left Thermocouple Lead Assembly
AMM 77-21-10-400-029	Installation of the Lower Right Thermocouple Lead Assembly

3. Fault Confirmation
Subtask 77-20-00-710-058-A ** ON A/C NOT FOR ALL

A. Do the operational test of the FADEC 2A on the ground (with engine non motoring) AMM 73-29-00-710-040.

Subtask 77-20-00-710-058-B ** ON A/C NOT FOR ALL

A. Do the operational test of the FADEC 2A on the ground (with engine non motoring) AMM 73-29-00-710-040.

4. Fault Isolation
Subtask 77-20-00-810-054-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message T495 SENS, J13, ECU:

do a check for open or short to ground of the harness J13 between the ECU (4000KS) and the 6 o'clock junction box, between the 6 o'clock junction box and the T495 thermocouple AWM 715109 and ASM 732515.

(1) If the wiring is not correct:

repair the above wiring.

(2) If the wiring is correct:

disconnect the harness J13 from the ECU (4000KS) and do a resistance check of the cable between:
. pins 12 and 13 (1 to 10 ohms)
. pins 12 and 24 (> 10 megohms)
. pin 12 and the ground (> 10 megohms).

(a) If the resistance values are in the specified limits:

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

(b) If the resistance values are out of the specified limits:

disconnect the harness CJ13 at the 6 o'clock junction box and do a resistance check of the harness CJ13 between:
. pins 3 and 13 (1 to 10 ohms)
. pins 3 and 12 (> 10 megohms)
. pin 3 and the ground (> 10 megohms).

1 If the resistance values are in the specified limits:

replace the harness J13 AMM 73-21-50-000-012 and AMM 73-21-50-400-012.

2 If the resistance values are out of the specified limits:

disconnect the harness CJ13 from the T495 thermocouple and do a resistance check of the T495 thermocouple between:
. pins A and B (1 to 10 ohms)
. pin A and the ground (> 10 megohms).

a If the resistance values are in the specified limits:

replace the harness CJ13 AMM 73-21-50-000-005 and AMM 73-21-50-400-005.

b If the resistance values are out of the specified limits, do an inspection/check of the T495 thermocouple wiring harness for isolation of the defective part AMM 77-21-10-200-001.

if the electrical check of one of the three two-probe lead assemblies is not correct, replace the defective thermocouple:
. the lower left-hand thermocouple lead assembly AMM 77-21-10-000-004 and AMM 77-21-10-400-004 or
. the lower right-hand thermocouple lead assembly AMM 77-21-10-000-005 and AMM 77-21-10-400-005 or
. the upper left-hand thermocouple lead assembly AMM 77-21-10-000-007 and AMM 77-21-10-400-007.
if the electrical check of the three-probe lead assembly is not correct:
. replace the three-probe thermocouple lead assembly AMM 77-21-10-000-003 and AMM 77-21-10-400-003.
if the electrical check of the upper extension lead is not correct:
. replace the upper extension lead AMM 77-21-10-000-001 and AMM 77-21-10-400-001.
if the electrical check of the lower extension lead is not correct:
. replace the lower extension lead AMM 77-21-10-000-006 and AMM 77-21-10-400-006.
if the electrical check of the main junction box assembly is not correct:
. replace the main junction box assembly AMM 77-21-10-000-002 and AMM 77-21-10-400-002.

Subtask 77-20-00-810-054-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message T495 SNSR, J13, ECU:

do a check for open or short to ground of the harness J13 between the ECU (4000KS) and the 6 o'clock junction box, between the 6 o'clock junction box and the T495 thermocouple AWM 715109 and ASM 732515.

(1) If the wiring is not correct:

repair the above wiring.

(2) If the wiring is correct:

disconnect the harness J13 from the ECU (4000KS) and do a resistance check of the cable between:
. pins 12 and 13 (1 to 10 ohms)
. pins 12 and 24 (> 10 megohms)
. pin 12 and the ground (> 10 megohms).

(a) If the resistance values are in the specified limits:

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

(b) If the resistance values are out of the specified limits:

disconnect the harness CJ13 at the 6 o'clock junction box and do a resistance check of the harness CJ13 between:
. pins 3 and 13 (1 to 10 ohms)
. pins 3 and 12 (> 10 megohms)
. pin 3 and the ground (> 10 megohms).

1 If the resistance values are in the specified limits:

replace the harness J13 AMM 73-21-50-000-012 and AMM 73-21-50-400-012.

2 If the resistance values are out of the specified limits:

disconnect the harness CJ13 from the T495 thermocouple and do a resistance check of the T495 thermocouple between:
. pins A and B (1 to 10 ohms)
. pin A and the ground (> 10 megohms).

a If the resistance values are in the specified limits:

replace the harness CJ13 AMM 73-21-50-000-005 and AMM 73-21-50-400-005.

b If the resistance values are out of the specified limits, do an inspection/check of the T495 thermocouple wiring harness for isolation of the defective part AMM 77-21-10-200-001.

if the electrical check of one of the three two-probe lead assemblies is not correct, replace the defective thermocouple:
. the lower left-hand thermocouple lead assembly AMM 77-21-10-000-004 and AMM 77-21-10-400-004 or
. the lower right-hand thermocouple lead assembly AMM 77-21-10-000-005 and AMM 77-21-10-400-005 or
. the upper left-hand thermocouple lead assembly AMM 77-21-10-000-007 and AMM 77-21-10-400-007.
if the electrical check of the three-probe lead assembly is not correct:
. replace the three-probe thermocouple lead assembly AMM 77-21-10-000-003 and AMM 77-21-10-400-003.
if the electrical check of the upper extension lead is not correct:
. replace the upper extension lead AMM 77-21-10-000-001 and AMM 77-21-10-400-001.
if the electrical check of the lower extension lead is not correct:
. replace the lower extension lead AMM 77-21-10-000-006 and AMM 77-21-10-400-006.
if the electrical check of the main junction box assembly is not correct:
. replace the main junction box assembly AMM 77-21-10-000-002 and AMM 77-21-10-400-002.

Subtask 77-20-00-810-054-C ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message T495 SNSR, J13, ECU:

do a check for open or short to ground of the harness HJ13 between the ECU (4000KS) and the 6 o'clock junction box, between the 6 o'clock junction box and the T495 thermocouple AWM 715109 and ASM 732515.

(1) If the wiring is not correct:

repair the above wiring.

(2) If the wiring is correct:

disconnect the harness HJ13 from the ECU (4000KS) and do a resistance check of the cable between:
. pins 12 and 13 (1 to 10 ohms)
. pins 12 and 24 (> 10 megohms)
. pin 12 and the ground (> 10 megohms).

(a) If the resistance values are in the specified limits:

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

(b) If the resistance values are out of the specified limits:

disconnect the harness CJ13 at the 6 o'clock junction box and do a resistance check of the harness CJ13 between:
. pins 3 and 13 (1 to 10 ohms)
. pins 3 and 12 (> 10 megohms)
. pin 3 and the ground (> 10 megohms).

1 If the resistance values are in the specified limits:

replace the harness HJ13 AMM 73-21-50-000-046 and AMM 73-21-50-400-046.

2 If the resistance values are out of the specified limits:

disconnect the harness CJ13 from the T495 thermocouple and do a resistance check of the T495 thermocouple between:
. pins A and B (1 to 10 ohms)
. pin A and the ground (> 10 megohms).

a If the resistance values are in the specified limits:

replace the harness CJ13 AMM 73-21-50-000-029 and AMM 73-21-50-400-029.

b If the resistance values are out of the specified limits, do an inspection/check of the T495 thermocouple wiring harness for isolation of the defective part AMM 77-21-10-200-002.

if the electrical check of one of the three two-probe lead assemblies is not correct, replace the defective thermocouple:
. the lower left-hand thermocouple lead assembly AMM 77-21-10-000-027 and AMM 77-21-10-400-027 or
. the lower right-hand thermocouple lead assembly AMM 77-21-10-000-029 and AMM 77-21-10-400-029 or
. the upper left-hand thermocouple lead assembly AMM 77-21-10-000-028 and AMM 77-21-10-400-028.
if the electrical check of the three-probe lead assembly is not correct:
. replace the three-probe thermocouple lead assembly AMM 77-21-10-000-026 and AMM 77-21-10-400-026, AMM 77-21-10-000-027 and AMM 77-21-10-400-027, AMM 77-21-10-000-028 and AMM 77-21-10-400-028, AMM 77-21-10-000-029 and AMM 77-21-10-400-029.
if the electrical check of the upper extension lead is not correct:
. replace the upper extension lead AMM 77-21-10-000-008 and AMM 77-21-10-400-008.
if the electrical check of the lower extension lead is not correct:
. replace the lower extension lead AMM 77-21-10-000-009 and AMM 77-21-10-400-009.
if the electrical check of the main junction box assembly is not correct:
. replace the main junction box assembly AMM 77-21-10-000-025 and AMM 77-21-10-400-025.

Subtask 77-20-00-710-059-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.A.

[Rev.8 from Aug 2018] 2026.04.04 04:37:43 UTC