Isuzu 4ja1, Workshop Manual

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6E-240 Engine Control System (4JH1)
Checks Action
Electromagnetic Interference (EMI)
and Electrical Noise Some electrical components/circuits are sensitive to EMI or other types of electrical
noise. Inspect for the following conditions:
•
A misrouted harness that is too close to high voltage/high current devices such as
injection components, motors, generator etc. These components may induce
electrical noise on a circuit that could interfere with normal circuit operation.
•
Electrical system interference caused by a malfunctioning relay, or the engine control
module (ECM) driven solenoid or switch. These conditions can cause a sharp
electrical surge. Normally, the problem will occur when the malfunctioning
component is operating.
•
Improper installation of non-factory or aftermarket add on accessories such as lights,
2-way radios, amplifiers, electric motors, remote starters, alarm systems, cell
phones, etc. These accessories may lead to an emission related failure while in use,
but do not fail when the accessories are not in use.
•
Test for an open diode across the A/C compressor clutch and for other open diodes.
Some relays may contain a clamping diode.
•
Test the generator for a bad rectifier bridge that may be allowing AC noise into the
electrical system.
Incorrect ECM Programming
•
There are only a few situations where reprogramming a ECM is appropriate:
Important:
DO NOT reprogram the ECM with the SAME software/calibration files that are already
present in the ECM. This is not an effective repair for any type of driveability problem.
- A ECM from another vehicle is installed.
- Revised software/calibration files have been released for this vehicle.
•
Verify that the ECM contains the correct software/calibration. If incorrect
programming is found, reprogram the ECM with the most current
software/calibration.
Duplicating Failure Conditions
•
If none of the previous tests are successful, attempt to duplicate and/or capture the
failure conditions.
•
An alternate method is to drive the vehicle with the DMM connected to a suspected
circuit. An abnormal reading on the DMM when the problem occurs, may help you
locate the problem.
scan tool Snapshot The scan tool can be set up to take a Snapshot of the parameters available via serial
data. The Snapshot function records live data over a period of time. The recorded data
can be played back and analyzed. The scan tool can also graph parameters singly or
in combinations of parameters for comparison. The Snapshot can be triggered
manually at the time the symptom is noticed, or set up in advance to trigger when a
DTC sets.
An abnormal value captured in the recorded data may point to a system or component
that needs to be investigated further.
Refer to the scan tool user instructions for more information on the Snapshot function.
Hard Start
Checks Action
DEFINITION:The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but
immediately dies.
Preliminary Checks
•
Diagnostic System Check - Engine Controls.
•
Ensure the driver is using the correct starting procedure.
•
Inspect the engine control module (ECM) and fuel injection pump control unit (PCU)
grounds for being clean, tight, and in their proper locations.
•
Inspect that the harness connectors are correctly connected.
•
Inspect the fuel type and quality.
•
Inspect the scan tool Data List in this section.
•
Inspect the Service Bulletins for ECM software updates.