Isuzu 2008MY N Series Workshop Manual page 319

1A-316 Engine Control System (4HK1)
Step
1. Turn OFF the ignition.
2. Disconnect the electric hydraulic control unit
(EHCU) harness connector if installed.
3. Disconnect the transmission control module
(TCM) harness connectors if installed.
4. Disconnect the data recording module (DRM)
or body control modul (BCM) harness
connector .
5. Turn ON the ignition, with the engine OFF.
6. Connect a DMM between the CAN Low circuit
(pin 16 of E-4) and a known good ground.
6
7. Connect a DMM between the CAN High circuit
(pin 15 of E-4) and a known good ground.
8. Test the CAN Low and High circuits (which
ever voltage reading did not read within the
specified value) between the ECM (pins 18
and 37 of J-14) and the VNT control module
(pins 15 and 16 of E-4) for an open circuit or
high resistance.
9. Repair the circuit(s) or connection(s) as
necessary.
Did you find and correct the condition?
1. Test the CAN Low and High circuits between
the IP cluster (pins 13 and 14 of B-105) and
the joint connection for an open circuit or high
resistance.
2. Inspect
connections and corrosion at the harness
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connector of the IP cluster (pins 13 and 14 of
B-105).
3. Repair the circuit(s) or connection(s) as
necessary.
Did you find and correct the condition?
1. Connect a DMM between the ignition voltage
feed circuit to the VNT control module (pin 13
of E-4) and a known good ground.
8
2. Turn ON the ignition, with the engine OFF.
Is the DMM voltage more than the specified
value?
Connect a DMM across the ignition voltage feed
circuit and ground circuit (pins 13 and 14 of E-4).
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Is the DMM voltage more than the specified
value?
Repair the open circuit or high resistance between
the ECM (15A) fuse and the VNT control module
10
(pin 13 of E-4). Check the ECM (15A) fuse first.
Did you complete the repair?
Repair the open circuit or high resistance between
the VNT control module (pin 14 of E-4) and the
ground terminal (E-9). Clean or tighten ground as
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necessary.
Did you complete the repair?
Action
for an intermittent,
Value(s)
1.5 to 3.5
volts
for poor
—
20.0 volts
20.0 volts
—
—
Yes
Go to Step 17 Go to Step 13
Go to Step 17 Go to Step 12
Go to Step 9 Go to Step 10
Go to Step 12 Go to Step 11
Go to Step 17
Go to Step 17
No
—
—