Isuzu 2008MY N Series Workshop Manual page 55

1A-52 Engine Control System (4HK1)
Step
Repair the open in the ignition voltage circuit to the
ECM.
6
Did you complete the repair?
1. Turn OFF the ignition.
2. Disconnect the scan tool from the DLC if
connected.
3. Measure the resistance across the CAN Low
and High circuits by probing the DLC (pins 6
7
and 14 of B-31).
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
connections and corrosion at the harness
connector of the ECM (pins 58 and 78 of J-
14).
4. Test the CAN Low and High serial data circuits
between the ECM (pins 58 and 78 of J-14)
and the DLC (pins 6 and 14 of B-31) for the
8
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 B-31) and
the ECM (pins 58 and 78 of J-14) or resistor
(pins 1 and 2 of B-302) for the following
conditions:
9
• A short to ground
• A short to voltage
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
Notice: An open in a ground circuit at the ECM will
not cause a loss of communication.
1. Check ECM
10
tightness.
2. Clean or tighten grounds as necessary.
Did you find and correct the condition?
Action
for an intermittent,
ground for corrosion
Value(s)
—
50 to 70 Ω
for poor
—
—
and
—
Yes
Go to Step 18
Go to Step 9 Go to Step 8
Go to Step 18 Go to Step 17
Go to Step 18 Go to Step 10
Go to Step 18 Go to Step 11
No
—