Isuzu 4ja1, Workshop Manual

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Engine Control System (4JH1) 6E-239
Checks Action
Electrical Connections or Wiring Poor electrical connections, terminal tension or wiring problems cause most
intermittent. To perform the following inspections:
•
Inspect for poor mating of the connector halves, or terminals improperly seated in the
connector body.
•
Inspect for improperly formed or damaged terminals. Test for poor terminal tension.
•
Inspect for poor terminal to wire connections including terminals crimped over
insulation. This requires removing the terminal from the connector body.
•
Inspect for 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.
•
Inspect for wires that are broken inside the insulation.
•
Inspect the harness for pinched, cut or rubbed through wiring.
•
Ensure that the wiring does not come in contact with hot exhaust components.
Control Module Power and Grounds
Component Power and Grounds 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.
Temperature Sensitivity
•
An intermittent condition may occur when a component/connection reaches normal
operating temperature. The condition may occur only when the
component/connection is cold, or only when the component/connection is hot.
•
If the intermittent is related to heat, review the data for a relationship with the
following:
- High ambient temperatures
- Under hood/engine generated heat
- Circuit generated heat due to a poor connection, or high electrical load
- Higher than normal load conditions, towing, etc.
•
If the intermittent is related to cold, review the data for the following:
- Low ambient temperatures–In extremely low temperatures, ice may form in a
connection or component. Test for water intrusion.
- The condition only occurs on a cold start.
- The condition goes away when the vehicle warms up.
•
Information from the customer may help to determine if the trouble follows a pattern
that is temperature related.