Isuzu 2008MY N Series Workshop Manual page 336

Circuit/ System Testing Exhaust Brake Control System Check (2 of 2)
Step
1. Install a scan tool.
2. Start the engine.
3. Apply the exhaust brake switch ON and OFF
while observing the Exhaust Brake Switch
1
parameter with a scan tool.
Does the scan tool indicate ON and OFF with
each switch transition?
Does the exhaust brake indicator lamp always
2
ON with each switch transition?
1. Turn OFF the ignition.
2. Disconnect the combination switch harness
connector (B-188).
3. Connect a test lamp between the voltage feed
3
circuit of combination switch harness (pin 13
of B-188) and a known good ground.
4. Start the engine.
Does the test lamp illuminate?
Observe the Exhaust Brake Switch parameter with
a scan tool while momentarily jumping 3-amp fused
jumper wire across the switch harness connector
between pins 13 and 15 of B-188.
4
Does the scan tool indicate ON when the
circuit is jumpered and OFF when the circuit is
not jumpered?
Repair the open circuit or high resistance between
the ECM (10A) fuse and the switch (pin 13 of B-
5
188). Check the ECM (10A) fuse first.
Did you complete the repair?
1. Test the signal circuit between the ECM (pin
45 of J-14) and the switch (pin 5of B-188) for
the following conditions:
• An open circuit
6
• A short to battery or ignition voltage
• High resistance
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
1. Inspect for an intermittent and for poor
connections at the harness connector of the
switch (pins 13 and 15 of B-188).
7
2. Repair the connection(s) as necessary.
Did you find and correct the condition?
1. Inspect for an intermittent and for a poor
connection at the harness connector of the
ECM (pin 45 of J-14).
8
2. Repair the connection(s) as necessary.
Did you find and correct the condition?
Repair or replace the combination switch.
9
Did you complete the repair or replacement?
Action
Engine Control System (4HK1)
Value(s) Yes
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Go to Step 2
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Go to Step 10
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Go to Step 4
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Go to Step 7
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Go to Step 20
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Go to Step 20
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Go to Step 20
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Go to Step 20
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Go to Step 20
1A-333
No
Go to Step 3
Go to Step 11
Go to Step 5
Go to Step 6
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Go to Step 8
Go to Step 9
Go to Step 19
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