Isuzu N 2008 Series Workshop Manual page 52

Step
1. Turn OFF the ignition.
2. Reconnect the ECM J14 harness connector.
3. Disconnect the scan tool from the DLC if
connected.
4. Measure the resistance across the CAN Low
14
and High circuits by probing the DLC (pins 6
and 14 of B31).
Is the resistance within the specified value (parallel
resistance of the 120 Ω resistor in the ECM and the
120 Ω CAN resistor should be 60 Ω)?
1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for
connections and corrosion at the harness
connector of the ECM (pins 58 and 78 of J14).
4. Test the CAN Low and High serial data circuits
between the DLC (pins 6 and 14 of B31) and
the ECM (pins 58 and 78 of J14), the
immobilizer control unit (ICU) (pins 5 and 6 of
15
B88) or the CAN resistor (pin 1 and 2 of B302)
for the following conditions:
• An open circuit
• A short circuit each other
• High resistance
5. Repair the connection(s) or circuit(s) as
necessary.
Did you find and correct the condition?
1. Test the CAN Low and High serial data circuits
between the DLC (pins 6 and 14 of B31) and
the ECM (pins 58 and 78 of J14), the ICU
(pins 5 and 6 of B88) or the CAN resistor (pins
1 and 2 of B302) for the following conditions:
16
• A short to ground
• A short to voltage
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
Important: Replacement
programmed and learned.
17
Replace the ECM. Refer to ECM Replacement.
Did you complete the replacement?
1. Turn OFF the ignition.
2. Reconnect all previously disconnected fuse,
relay or harness connector(s).
3. Turn ON the ignition, with the engine OFF.
18
4. Attempt to establish communication with the
ECM.
Does the scan tool communicate with the ECM?
Action
an intermittent, for
ECM must
Engine Control System (4JJ1)
Value(s)
50 to 70 Ω
poor
—
—
be
—
—
Yes
Go to Step 16 Go to Step 15
Go to Step 18 Go to Step 17
Go to Step 18 Go to Step 17
Go to Step 18
System OK Go to Step 3
1A-49
No
—