ISUZU 4JJ3 Engine Description of Symptom Intermittent Conditions

Intermittent Conditions of ISUZU 4JJ3 Engine Description of Symptom

 

1 Important preliminary inspections before starting

Before using the symptom list, perform the Diagnostic System Check – Engine Controls and check all of the following items.

The MIL or SVS indicator light is functioning properly (Euro4).

The check engine warning light is operating normally (Except Euro4).

The scan tool data is within the normal range of operation values.

If checking the customer’s complaint and verifying the applicable symptom in the table of contents, inspect the items presented for the symptom.

 

2 Visual inspection and actual inspection

Careful visual inspection and actual inspection are required for some symptom procedures. This procedure is extremely important. By conducting visual and actual inspections, it is possible to save valuable time by fixing problems without performing further inspections. Check for the following items.

 

The ground of the ECM should be clean and firmly secured in the correct position.

The vacuum hose should be correctly connected without cracking or twisting.

Conduct a thorough inspection to make sure that there are no leaks or clogging in the vacuum hose.

The air intake duct should not be crushed or damaged.

The exhaust pipe should not be crushed or damaged.

The wiring and terminals of engine harnesses should be appropriately connected, and they should not be pinched or disconnected.

 

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3 Intermittent conditions

If an intermittent condition exists, inspect for improper installation of electronic equipment. Inspect whether there is any electronic equipment, light, or mobile phone that was additionally installed. Verify that devices that were additionally installed are not connected to serial data circuits such as CAN.

 

Depending on the problem, the MIL or SVS indicator light may not illuminate, or a DTC may not be stored. An intermittent condition is often caused by an improper electrical connection or wiring. Conduct a careful visual inspection, or conduct an actual inspection to see whether the following conditions exist in the suspected connector. (Euro4)

 

Depending on the problem, the check engine warning light may not illuminate, or a DTC may not be stored. An intermittent condition is often caused by an improper electrical connection or wiring. Conduct a careful visual inspection, or conduct an actual inspection to see whether the following conditions exist in the suspected connector. (Except Euro4)

 

Incomplete connection between connectors

Seating failures of terminals

Damage or deformation of terminals

Repair or replace the connector terminal of the circuit with the problem, and appropriately connect. Remove the terminals from the connector body and inspect the wires of the terminals for poor connections.

 

Connect the DMM to the suspected circuit and perform a vehicle road test. If an abnormal value is displayed when the malfunction occurs, it can be determined that there is a problem in the monitored circuit. The scan tool is useful in detecting intermittent conditions. The scan tool has the following convenient functions.

 

The snapshot function can be used to record the engine parameters.

The snapshot function can be used to review the recorded information and know the particular operation condition that resulted in the malfunction.

Review the information recorded in the Freeze Frame/Failure Records, store the Freeze Frame/Failure Records, and operate the vehicle under the DTC set conditions.

By using the plot function of the scan tool, it is possible to graph the selected data parameters.

The plot function of the scan tool can be used to review the recorded information and check the location of the intermittent condition.

In order to detect intermittent conditions, use the data recording function of the data recording module (DRM). The DRM includes a function for storing engine log data when a DTC is set. If an entry exceeding the maximum storage count is set, the oldest log data is overwritten. The manual trigger switch stores the log data when voluntarily operated by the driver on the occasion of an incorrect vehicle performance event, as opposed to when a DTC event occurs. If the driver presses and releases the manual trigger switch once, that time becomes a trigger, and any log data after the trigger is stored in the DRM memory. When there is available space in the DRM memory, the log data is stored in that space. However, if an entry exceeding the maximum storage count is set, the oldest log data is overwritten.

 

If there is an intermittent condition that may cause the engine to stall after starting, check for a DTC relating to the vehicle anti-theft system (immobilizer).

 

Check for improper installation of optional electronic equipment such as lights or mobile phones. Under the following conditions, DTCs are not recorded, and the MIL or SVS indicator light may illuminate intermittently. (Euro4)

 

Check for improper installation of optional electronic equipment such as lights or mobile phones. Under the following conditions, DTCs are not recorded, and the check engine warning light may illuminate intermittently. (Except Euro4)

 

The ground of the ECM is loose or dirty.

The MIL circuit or SVS indicator light circuit is intermittently shorted to ground (Euro4).

The check engine warning light circuit is intermittently shorted to ground (Except Euro4).

The diode has an open circuit.

Note:

 

A relay, ECM drive solenoid, or switch malfunction may cause the generation of a large surge voltage or surge current. Normally, this problem will occur when the malfunctioning component is operating.

In the following list of symptoms, causes for each symptom are organized. There is no significance to the order of this procedure. If the value on the scan tool does not indicate a malfunction, the next procedure to perform should be the one that can be most easily inspected or is most likely to be the cause.

Use the following list when diagnosing symptoms of complaints.

 

Intermittent engine conditions

Hard start

Rough, unstable

High idle speed

Cuts out

Surges

Lack of power, sluggishness or sponginess

Hesitation, sag or stumble

Abnormal combustion noise

Poor fuel economy

Black smoke

White smoke

There is no current problem, but a past DTC exists. Or, there is a complaint from the customer not related to a DTC, and that symptom cannot be reproduced.

 

4 Preliminary inspection

Perform the Diagnostic system check – engine controls.

 

5 Wire harness and connector

Intermittent open or short circuits may be caused by vibrations in the wire harnesses and connectors due to fluctuations in engine torque, bumps in the road, etc. Perform the following inspections.

 

Shake the related connectors or wiring while monitoring the scan tool data.

Shake the related connectors or wiring and monitor component operation while turning the components ON and OFF using the scan tool.

Start the engine, and shake the related connectors and wiring while checking the operation status of the engine.

If moving the wire harness or connector affects the data displayed or the component or system operation, inspect the wire harness and connector as necessary.

 

6 Electrical connections or wiring

Intermittent conditions are caused by poor wire harness connections, loose terminals, or problems in the wire harness. Check for the following conditions.

 

Is there any improper mating of the connector halves or improper seating of the terminals in the connector body?

Are there any improperly formed, damaged, or loose terminals?

Are there any poor terminal-to-wire harness connections or bent terminals?

Is there any corrosion or water intrusion?

Are there any broken wire harnesses?

Is the wire harness pinched, cut, or damaged?

Is the wire harness coming in contact with hot exhaust components?

Note:

 

Worn or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation, with little visible evidence. Check for swollen or stiff sections of the wire harness in the suspected circuits.

 

7Control module power supply and ground, and component power supply and ground

Various symptoms can occur due to poor connections at the power supply or ground.

Test all control module power supply circuits. In many vehicles, there are multiple circuits that supply power to the control module. Other components in the system have separate power supply circuits that also need to be tested. Inspect the connections and fuses of the module and the component connectors, as well as intermediate connections between the power supply, the module, and the components. A test lamp or a DMM may indicate that voltage is present, but neither of them tests whether the circuit is carrying sufficient current. Check whether sufficient current necessary to operate the components is flowing in the circuit.

Test all control module ground circuits and system ground circuits. Some control modules have multiple ground circuits. Other components in the system have a separate ground that also needs to be tested. Inspect whether the ground is clean and is securely connected to the ground point. Inspect the connections of the components and the splice pack. Check whether sufficient current necessary to operate the components is flowing in the circuit.

 

8 Effects caused by temperature

An intermittent condition may occur when a component or connection reaches its operating temperature. For intermittent conditions that may occur only when the components or connections are cold or only when they are hot, failure records or snapshot data can be helpful, where possible.

If an intermittent condition is related to heat, review the data relating to the following items.

 

High ambient temperature

Heat generated under the hood and by the engine

Heat generated due to poor wire harness connections or a high electrical load

Higher than normal load conditions due to towing, etc.

If an intermittent condition is related to low temperatures, review the data relating to the following.

 

Low ambient temperature

The symptom occurs only on a cold start.

The symptom goes away when the vehicle warms up.

Note:

 

If the temperature is extremely low, a connection area or component may freeze. Inspect for water intrusion.

Based on the information from the customer, determine if the failure is caused by temperature.

 

9 EMI and electrical noise

Some electronic components and circuits are sensitive to EMI or other types of electrical noise.

Inspect for wire harnesses that are placed too close to high-voltage or high-current components such as injection components, motors, and generators. These components may generate electrical noise which interferes with normal circuit operations.

Check for a surge voltage or surge current generated by a relay or switch malfunction. Normally, this problem will occur when the malfunctioning component is operating.

Inspect for improper installation of non-factory or aftermarket electronic equipment such as lights, radios, amplifiers, electric motors, remote starters, and alarm systems. Electromagnetic disturbance may occur while this electronic equipment is in use, but not when not in use.

Inspect the generator for a malfunctioning rectifier circuit that may be allowing AC noise into the electrical system.

 

10 Incorrect ECM programming

The situations in which reprogramming an ECM is appropriate are limited.

 

An ECM from another vehicle is installed.

A revised software/calibration file has been released for this vehicle.

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 a drivability problem.

 

Check that the ECM contains the correct software/calibration. If an incorrect program is found, use the most recent software/calibration to reprogram the ECM.

 

11 Reproduction of failure conditions

If none of the previous tests are successful, attempt to duplicate or record the failure conditions.

An alternative method is to operate the vehicle with the DMM connected to the suspected circuit. If an abnormal value is displayed on the DMM when the problem occurs, this can be helpful in identifying the defective area.

 

12 Scan tool snapshot

Snapshots can be taken using the scan tool. The snapshot function can be used to record ECU data in chronological order and analyze it. The scan tool also has a graph function which can display graph data individually or in combination for comparison. The snapshot function can be used to set up the manual trigger or automatic trigger when a DTC is set.

Analyzing the recorded data allows malfunctioning components to be identified.

 

13 DRM memory

Use the data stored in the DRM, or use the manual trigger switch. The DRM has the ability to store the engine log data at the time of a DTC event. The manual trigger switch stores the log data by an arbitrary operation of the driver on the occurrence of a wrong vehicle performance event instead of a DTC event. If the driver presses and releases the manual trigger switch once, that time becomes a trigger, and the log data after the trigger is stored in the DRM memory.

 

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