Before starting the intermittent inspection, perform the diagnostic system check-differential lock controls to verify that all the following conditions are met.
Some of the symptom repair procedures require a careful visual inspection and physical inspection. This step is extremely important. Problems may be corrected just by carrying out the visual and physical inspections without performing any further inspection, which leads to saving of valuable time. Check the following points.
If an intermittent condition exists, inspect for improperly installed electronic equipment. Inspect for any aftermarket add-on electronic devices, lights, or mobile phones. Verify that no aftermarket equipment is connected to the serial data circuit. If an intermittent condition cannot be identified, communication signals from mobile phones may be causing the symptom. Even if a problem occurs and the rear differential lock failure warning light turns ON, a DTC may not be stored. Most intermittent conditions are caused by poor electrical connections or wiring. Carefully inspect suspected connectors visually and physically for the following conditions.
Repair or replace the connector terminals in the circuit with a problem in order to ensure proper contact pressure. Disconnect the terminal from the connector body in order to inspect for poor terminal-to-wire connections. Connect the DMM to the suspected circuit and perform a vehicle road test. Abnormal readings that follow any malfunctions that occur are indications that there is a malfunction in the circuit being monitored. If any of the following is the cause of the problem, no DTC is stored, but the rear differential lock failure warning light illuminates intermittently.
Note
If there are no abnormal scan tool readings, proceed in a logical order, starting with items that are easiest to inspect, or those that are most likely. The problem is not currently present but is recorded in the DTC history. Or, there is a customer complaint, but the symptom cannot currently be reproduced because the problem is not DTC-related.
Before starting, perform the required preliminary inspection and the visual inspection.
Many of the circuits that are intermittently having an open circuit or short circuit are often affected by the movements of harnesses/connectors due to vibrations, engine torque, bumps on a road, rough pavements, etc. It is recommended to test for this type of condition by performing the applicable procedure from the following list.
If moving the harness or connector affects the data displayed or system operation, inspect the harness or the connector, and repair as necessary.
Most intermittent conditions are caused by poor electrical connections, loose terminals, or wiring problems. Perform the following inspections.
Note
Poor power supply 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 have separate power supply circuits that may also need to be tested. Inspect the module, component connectors, fuse connections, as well as any other intermediate connections between the power supply, modules, and components. A test lamp or a DMM is capable of indicating whether or not any voltage is present, but neither of them has the ability to test whether sufficient current is flowing in the circuit. Ensure that the circuit can carry the current necessary to operate the components.
Test all control modules and system ground circuits. The control modules may have multiple ground circuits. Other components in the system have separate grounds that also need to be tested. Inspect the ground points for contamination or improper tightening. Inspect the connections at the component and in splice packs where applicable. Ensure that the circuit can carry the current necessary to operate the components.
An intermittent condition may occur when a component or connection reaches the normal operating temperature. The condition may occur only when the temperature of the component or connection is low or high.
If the intermittent condition is caused by heat, check the data relating to the following items.
If the intermittent condition is attributed to low temperature, check the data related to the following items.
Note
Based on the information from the customer, determine if the failure is caused by temperature.
Some electronic components and circuits are sensitive to EMI or other types of electrical noise.
Inspect whether the harnesses are placed too close to high-voltage or high-current devices such as injection components, motors, and generators. These components may generate electrical noises which interfere with normal circuit operations.
Inspect the electrical system interference caused by a malfunctioning actuator or switch.
Such interference may cause a large electrical surge to be generated. 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, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, and mobile phones.
Electromagnetic disturbance may occur while these electronic components are in use, but may not occur when not in use.
Inspect the generator for a malfunctioning rectifier circuit that may be allowing AC noise into the electrical system.
If none of the above tests are successful, try to duplicate and record the failure conditions.
To test this, drive the vehicle with the DMM connected to a suspected circuit. An abnormal reading on the DMM when the problem occurs may help identify the problem.
The scan tool can be set up to take a snapshot of the parameters available via serial data. The snapshot function records live data in chronological order. The recorded data can be replayed and analyzed. The scan tool also has a graph function which can be used to graph parameters individually or in combination with other parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed or set up in advance to be triggered 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.