Isuzu N 2008 Series Workshop Manual page 218

Step
1. Leave the DMM connected to the boost
pressure sensor harness connector.
2. Turn OFF the ignition.
3. Disconnect the intake throttle valve harness
5
connector.
4. Turn ON the ignition, with the engine OFF.
Does the DMM voltage change to more than the
specified value?
1. Leave the DMM connected to the boost
pressure sensor harness connector.
2. Turn OFF the ignition.
3. Disconnect the crankshaft position (CKP)
6
sensor harness connector.
4. Turn ON the ignition, with the engine OFF.
Does the DMM voltage change to more than the
specified value?
Notice: If no variable nozzle turbocharger (VNT) is
installed, skip to Step 8.
1. Leave the DMM connected to the boost
pressure sensor harness connector.
2. Turn OFF the ignition.
7
3. Disconnect the vacuum pressure sensor
harness connector.
4. Turn ON the ignition, with the engine OFF.
Does the DMM voltage change to more than the
specified value?
Notice: If no exhaust differential pressure sensor is
installed, skip to Step 9.
1. Leave the DMM connected to the boost
pressure sensor harness connector.
2. Turn OFF the ignition.
8
3. Disconnect the exhaust differential pressure
sensor harness connector.
4. Turn ON the ignition, with the engine OFF.
Does the DMM voltage change to more than the
specified value?
1. Test the 5 volts reference circuit 3 between the
ECM (pin 80 of J14) and the exhaust
differential pressure sensor (pin 3 of J33) for a
short to ground or short to the low reference
circuit.
2. Test the 5 volts reference circuit 4 between the
ECM (pin 95 of E12) and the following
components for a short to ground or short to
the low reference circuit:
9
• CKP sensor (pin 3 of E20)
• Boost pressure sensor (pin 3 of E24)
• Intake throttle position sensor (pin 6 of
E16)
• Vacuum pressure sensor (pin 3 of E34)
3. Repair the circuit(s) as necessary.
Did you find and correct the condition?
Action
Engine Control System (4JJ1)
Value(s) Yes
4.5 volts
Go to Step 12
4.5 volts
Go to Step 13
4.5 volts
Go to Step 14
4.5 volts
Go to Step 15
—
Go to Step 17
1A-215
No
Go to Step 6
Go to Step 7
Go to Step 8
Go to Step 9
Go to Step 16