4. Fault Isolation
_______________

 A. The failure message is generated if both channel A and channel B signals are invalid or out of range.
 (1) If the failure messages N2 SNSR, J7, ECU and N2 SNSR, J8, ECU are not
 confirmed: R
R (a) No maintenance action is required.
 (2) If the failure messages N2 SNSR, J7, ECU and N2 SNSR, J8, ECU are not confirmed but are repetitive:
 - disconnect HJ7 harness from the N2 sensor (N2-A connector) and disconnect HJ8 harness from the N2 sensor (N2-B connector).
R (a) Visually examine the receptacles and the connectors for damaged R pins or contamination (Ref. AMM TASK 73-21-50-210-002).
 1 If damage is found:
_ - repair or replace as required.

 2 If no damage is found:
_

 - do a cleaning of the connectors and receptacles using a bristle brush with stoddard solvent (Material No. CP2011) (Ref. AMM TASK 73-21-50-210-002).
 (b) If the failure continues during the subsequent flights:

 - replace the SENSOR-N2 ROTATIONAL SPD (4001EV) (Ref. AMM TASK 77-11-20-000-002) and (Ref. AMM TASK 77-11-20-400-002).

 (c) If the failure continues during the subsequent flights:

 - replace the ECU (4000KS) (Ref. AMM TASK 73-21-60-000-001) and (Ref. AMM TASK 73-21-60-400-001).

 (d) If the failure continues during the subsequent flights:

 - replace the HJ7 harness (Ref. AMM TASK 73-21-50-000-040) and (Ref. AMM TASK 73-21-50-400-040).

 (e) If the failure continues during the subsequent flights:

 - replace the HJ8 harness (Ref. AMM TASK 73-21-50-000-041) and (Ref. AMM TASK 73-21-50-400-041).
 (3) If the failure message N2 SNSR, J7, ECU is confirmed:
 - disconnect the HJ7 harness from the N2 sensor (N2-A connector).
R (a) Visually examine the receptacles and the connectors for damaged R pins or contamination (Ref. AMM TASK 73-21-50-210-002).
 1 If damage is found:
_ - repair or replace as required.

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 2 If no damage is found:

_ R - do the electrical resistance test through the N2 sensor R (4001EV) (channel A) between:
 . pins 1 and 2 (40 to 80 ohms) . pins 1 and 3 (>10 megohms)
R . pin 1 and the ground (>10 megohms).
 a If the resistance values are out of the specified limits:
_

 - replace the N2 sensor (4001EV) (Ref. AMM TASK 77-11-20-000-002) and (Ref. AMM TASK 77-11-20-400-002).
 b If the resistance values are in the specified limits:
_ R - connect the HJ7 harness to the N2 sensor.
R (b) Disconnect connector HJ7 from the ECU (4000KS) receptacle and R visually examine the receptacles and the connectors for damaged R pins or contamination (Ref. AMM TASK 73-21-50-210-002).
 1 If damage is found:
_ - repair or replace as required.

 2 If no damage is found:
_

 - do the electrical resistance test through the HJ7 harness between: . pins 2 and 11 (40 to 80 ohms) . pins 2 and 3 (>10 megohms)
R . pin 2 and the ground (>10 megohms).
 a If the resistance values are in the specified limits:
_

 - replace the ECU (4000KS) (Ref. AMM TASK 73-21-60-000-001) and (Ref. AMM TASK 73-21-60-400-001).
 b If the resistance values are out of the specified limits:
_

 - replace the HJ7 harness (Ref. AMM TASK 73-21-50-000-040) and (Ref. AMM TASK 73-21-50-400-040).
 (4) If the failure message N2 SNSR, J8, ECU is confirmed:
 - disconnect the HJ8 harness from the N2 sensor (N2-B connector).
R (a) Visually examine the receptacles and the connectors for damaged R pins or contamination (Ref. AMM TASK 73-21-50-210-002).
 1 If damage is found:
_ - repair or replace as required.

 2 If no damage is found:
_ R - do the electrical resistance test through the N2 sensor R (4001EV) (channel B) between:
 . pins 1 and 2 (40 to 80 ohms) . pins 1 and 3 (>10 megohms)
R . pin 1 and the ground (>10 megohms).
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 a If the resistance values are out of the specified limits:

_

 - replace the N2 sensor (4001EV) (Ref. AMM TASK 77-11-20-000-002) and (Ref. AMM TASK 77-11-20-400-002).
 b If the resistance values are in the specified limits:
　
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