Alternator Fr Signal Circuit Troubleshooting - Honda 2002 Accord Manual

Idle Control System
Alternator FR Signal Circuit Troubleshooting
1. Disconnect the 4P connector from the alternator.
2. Turn the ignition switch ON (II).
3. Measure voltage between ECM/PCM connector
terminals B20 and C5.
B (25P)
E C M / P C M C O N N E C T O R S
1
2 3
4 5
/
7 8
9
10
11 12 13 14
/
16 17 18
19
20
21 22 23
24
25
LG1 ( B R N / B L K )
C (31P)
A L T F ( W H T / R E D )
1 2 3
/
5 6 7 8 9
10
/ /
13 14 15 16 17 18 19 20 21
/
23 24 25
2 6
27
28
29 30
/
W i r e s i d e o f f e m a l e t e r m i n a l s
Is there approx. 5V?
Y E S - G o to step 4.
N O - G o t o step 14.
4. Turn the ignition switch O F F .
5. Reconnect the alternator 4P connector.
6. Start the engine. Hold the engine at 3,000 rpm with
no load (in Park or neutral) until the radiator fan
comes on, then let it idle.
7. Measure voltage between ECM/PCM connector
terminals B20 and C5.
Does the voltage decrease when the headlights
and rear window defogger are turned on?
Y E S - T h e A L T FR signal is O K . B
N O - G o t o step 8.
8. Turn the ignition switch O F F .
9. Disconnect the negative cable from the battery.
10. Disconnect ECM/PCM connector C (31P).
11. Disconnect the ALT 4P connector.
12. Connect the alternator 4P connector terminal No. 4 to
body ground with a jumper wire.
A L T 4 P C O N N E C T O R
1 2
3 4
A L T F ( W H T / R E D )
J U M P E R W I R E
W i r e s i d e o f f e m a l e t e r m i n a l s
13. Check for continuity between body ground and
ECM/PCM connector terminal C5.
E C M / P C M C O N N E C T O R C (31P)
A L T F ( W H T / R E D )
1
2 3
/
5 6 7 8 9 10
/ /
13 14 15 16 17 18 19 20 21
y
23 24 25 26 27 28
29 30
V
W i r e s i d e o f f e m a l e t e r m i n a l s
Is there continuity?
Y E S —Troubleshoot the charging circuit
(see page 4-29). •
NO —Repair open in the wire between the E C M /
PCM <C5) and the alternator. •
14. Turn the ignition switch OFF.
15. Disconnect the negative cable from the battery.
16. Disconnect ECM/PCM connector C (31P).
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