Intermittent Conditions - Isuzu N 2008 Series Workshop Manual

Intermittent Conditions

Checks
Definition:
The problem is not currently present but is indicated in DTC History.
OR
There is a customer complaint, but the symptom cannot currently be duplicated, if the problem is not DTC related.
Preliminary Checks
Harness/ Connector
Electrical Connections or Wiring
Control Module Power and Grounds
Component Power and Grounds
• Refer to Symptoms - Engine Controls before starting.
Many intermittent open or shorted circuits are affected by harness/ connector
movement that is caused by vibration, engine torque, bumps/ rough pavement, etc.
Test for this type of condition by performing the applicable procedure from the following
list:
• Move related connectors and wiring while monitoring the appropriate scan tool data.
• Move related connectors and wiring with the component commanded ON, and OFF,
with the scan tool. Observe the component operation.
• With the engine running, move related connectors and wiring while monitoring
engine operation.
If harness or connector movement affects the data displayed, component/ system
operation, or engine operation, inspect and repair the harness/ connections as
necessary.
Poor electrical connections, terminal tension or wiring problems cause most
intermittent. To perform the following inspections:
• Poor mating of the connector halves, or terminals improperly seated in the
connector body.
• Improperly formed or damaged terminals. Test for poor terminal tension.
• Poor terminal to wire connections including terminals crimped over insulation. This
requires removing the terminal from the connector body.
• Corrosion/ water intrusion. Pierced or damaged insulation can allow moisture to
enter the wiring. The conductor can corrode inside the insulation, with little visible
evidence. Look for swollen and stiff sections of wire in the suspect circuits.
• Wires that are broken inside the insulation.
• Harness for pinched, cut or rubbed through wiring.
• Ensure that the wiring does not come in contact with hot exhaust components.
Poor power or ground connections can cause widely varying symptoms.
• Test all control module power supply circuits. Many vehicles have multiple circuits
supplying power to the control module. Other components in the system may have
separate power supply circuits that may also need to be tested. Inspect connections
at the module/ component connectors, fuses, and any intermediate connections
between the power source and the module/ component. A test lamp or a DMM may
indicate that voltage is present, but neither tests the ability of the circuit to carry
sufficient current. Ensure that the circuit can carry the current necessary to operate
the component.
• Test all control module ground and system ground circuits. The control module may
have multiple ground circuits. Other components in the system may have separate
grounds that may also need to be tested. Inspect grounds for clean and tight
connections at the grounding point. Inspect the connections at the component and
in splice packs, where applicable. Ensure that the circuit can carry the current
necessary to operate the component.
Engine Control System (4JJ1)
Action
1A-323