Failure of the Bleed Bias System on Engine 1

TASK 75-30-00-810-839-B
Failure of the Bleed Bias System on Engine 1

1. Possible Causes

harness J15
ECU [4000KS]
bleed bias transducer

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
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 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)
AMM 75-34-10-000-001	Removal of the Bleed Bias Transducer
AMM 75-34-10-400-001	Installation of the Bleed Bias Transducer

3. Fault Confirmation
Subtask 75-30-00-710-150-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the operational test of the FADEC 1B on the ground (with engine non motoring) AMM 73-29-00-710-040.

4. Fault Isolation
Subtask 75-30-00-810-104-A ** ON A/C NOT FOR ALL

A. If the CLASS 3 FAULTS page gives the maintenance message WB3 SENS, J15, ECU:

do a check for open or short to ground in the harness J15 between the ECU (4000KS) and the bleed bias transducer.

(1) If the wiring is not correct:

repair the above wiring.

(2) If the wiring is correct:

disconnect the connector J15 from the ECU (4000KS) and do a resistance check of the cable between:
For the channel B
. pins 47 and 27 (55 to 90 ohms)
. pins 14 and 28 (2600 to 3500 ohms)
. pins 29 and 28 (2600 to 3500 ohms)
. pins 47 and 13 (> 10 megohms)
. pins 14 and 13 (> 10 megohms)
. pins 29 and 13 (> 10 megohms)
. pin 47 and the ground (> 10 megohms)
. pin 14 and the ground (> 10 megohms)
. pin 29 and the ground (> 10 megohms)
For the channel B
. pins 3 and 22 (55 to 90 ohms)
. pins 10 and 9 (2600 to 3500 ohms)
. pins 23 and 9 (2600 to 3500 ohms)
. pins 3 and 7 (> 10 megohms)
. pins 10 and 7 (> 10 megohms)
. pins 23 and 7 (> 10 megohms)
. pin 3 and the ground (>10 megohms)
. pin 10 and the ground (> 10 megohms)
. pin 23 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 connector J15 from the bleed bias transducer and do a resistance check of the transducer between:
. pins 1 and 2 (55 to 90 ohms)
. pins 3 and 4 (2600 to 3500 ohms)
. pins 5 and 4 (2600 to 3500 ohms)
. pin 1 and the ground (> 10 megohms)
. pin 3 and the ground (> 10 megohms)
. pin 5 and the ground (> 10 megohms).

1 If the resistance values are in the specified limits:

replace the harness J15 .

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

replace the bleed bias transducer AMM 75-34-10-000-001 and AMM 75-34-10-400-001.

Subtask 75-30-00-810-104-B ** ON A/C NOT FOR ALL

A. If the CLASS 3 FAULTS page gives the maintenance message BLD SNSR, J15, ECU:

do a check for open or short to ground in the harness J15 between the ECU (4000KS) and the bleed bias transducer.

(1) If the wiring is not correct:

repair the above wiring.

(2) If the wiring is correct:

disconnect the connector J15 from the ECU (4000KS) and do a resistance check of the cable between:
For the channel B
. pins 47 and 27 (55 to 90 ohms)
. pins 14 and 28 (2600 to 3500 ohms)
. pins 29 and 28 (2600 to 3500 ohms)
. pins 47 and 13 (> 10 megohms)
. pins 14 and 13 (> 10 megohms)
. pins 29 and 13 (> 10 megohms)
. pin 47 and the ground (> 10 megohms)
. pin 14 and the ground (> 10 megohms)
. pin 29 and the ground (> 10 megohms)
For the channel B
. pins 3 and 22 (55 to 90 ohms)
. pins 10 and 9 (2600 to 3500 ohms)
. pins 23 and 9 (2600 to 3500 ohms)
. pins 3 and 7 (> 10 megohms)
. pins 10 and 7 (> 10 megohms)
. pins 23 and 7 (> 10 megohms)
. pin 3 and the ground (>10 megohms)
. pin 10 and the ground (> 10 megohms)
. pin 23 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 connector J15 from the bleed bias transducer and do a resistance check of the transducer between:
. pins 1 and 2 (55 to 90 ohms)
. pins 3 and 4 (2600 to 3500 ohms)
. pins 5 and 4 (2600 to 3500 ohms)
. pin 1 and the ground (> 10 megohms)
. pin 3 and the ground (> 10 megohms)
. pin 5 and the ground (> 10 megohms).

1 If the resistance values are in the specified limits:

replace the harness J15 .

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

replace the bleed bias transducer AMM 75-34-10-000-001 and AMM 75-34-10-400-001.

Subtask 75-30-00-710-151-A ** ON A/C NOT FOR ALL

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

[Rev.8 from Aug 2018] 2026.04.04 04:37:10 UTC