Isuzu 4JA1 Workshop Manual page 327

Step
5 1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the
signal circuit and the low reference circuit of the
IAT sensor harness (pins 1 and 3 of C-116
connector).
3. Turn ON the ignition, with the engine OFF.
4. Observe the IAT parameter with the scan tool.
Is the IAT parameter more than the specified value?
6 1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the
signal circuit of the IAT sensor harness (pin 1 of
C-116 connector) and a known good ground.
3. Turn ON the ignition, with the engine OFF.
4. Observe the IAT parameter with the scan tool.
Is the IAT parameter more than the specified value?
7 1. Test the signal circuit between the ECM (pin 3 of
C-57 connector) and the IAT sensor (pin 1 of C-
116 connector)
resistance.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
8 1. Test the low reference circuit between the ECM
(pin 14 of C-57 connector) and the IAT sensor
(pin 3 of C-116 connector) for an open circuit or
high resistance.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
9 1. Test the signal circuit between the ECM (pin 3 of
C-57 connector) and the IAT sensor (pin 1 of C-
116 connector) for a short to any 5 volts
reference circuit.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
10 1. Turn OFF the ignition.
2. Inspect for
connections at the harness connector of the IAT
sensor (pins 1 and 3 of C-116 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition?
11 1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for
connections on the IAT sensor circuits at the
harness connector of the ECM (pins 3 and 14 of
C-57 connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition?
12 Replace the IAT sensor. Refer to Mass Air Flow
Sensor Replacement in this section. (IAT sensor is
internal to MAF sensor)
Did you complete the replacement?
13 Important: Replacement
programmed.
Replace the ECM. Refer to Engine Control Module
(ECM) Replacement in this section.
Did you complete the replacement?
Action
for an open circuit
an intermittent and for
an intermittent and for
ECM must
Value(s)
110°C (230°F)
110°C (230°F)
high
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
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poor

poor
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
be

Engine Control System (4JH1) 6E-73
Yes
Go to Step 9 Go to Step 6
Go to Step 8 Go to Step 7
Go to Step 14 Go to Step 11
Go to Step 14 Go to Step 11
Go to Step 14 Go to Step 10
Go to Step 14 Go to Step 12
Go to Step 14 Go to Step 13
Go to Step 14
Go to Step 14
No
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