Testing for Intermittent Conditions and Poor Connections |
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J 35616 GM-Approved Terminal Test Kit |
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J-38125 Terminal Repair Kit |
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Wiring broken inside the insulation |
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Poor connection between the male and female terminal at a connector |
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Poor terminal to wire connection-Some conditions which fall under this description are poor crimps, poor solder joints, crimping over the wire insulation rather than the wire itself, and corrosion in the wire to terminal contact area, etc. |
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Pierced or damaged insulation can allow moisture to enter the wiring causing corrosion. The conductor can corrode inside the insulation, with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits. |
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Wiring which has been pinched, cut, or its insulation rubbed through may cause an intermittent open or short as the bare area touches other wiring or parts of the vehicle. |
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Wiring that comes in contact with hot or exhaust components |
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Refer to Inducing Intermittent Fault Conditions in order to duplicate the conditions required, in order to verify the customer concern. |
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Refer to Testing for Electrical Intermittents for test procedures to detect intermittent open, high resistance, short to ground, and short to voltage conditions. |
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Refer to Scan Tool Snapshot Procedure for advanced intermittent diagnosis and Vehicle Data Recorder operation. |
Testing for Terminal Fretting |
Testing for Proper Terminal Contact |
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Separate the connector halves. |
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Visually inspect the connector halves for contamination. Contamination may result in a white or green build-up within the connector body or between terminals. This causes high terminal resistance, intermittent contact, or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals, and connector body. |
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Using an equivalent male terminal from the J-38125 , test that the retention force is significantly different between a good terminal and a suspect terminal. Replace the female terminal in question. |
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Remove the component in question. |
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Visually inspect each side of the connector for signs of contamination. Avoid touching either side of the connector as oil from your skin may be a source of contamination as well. |
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Visually inspect the terminal bearing surfaces of the flat wire circuits for splits, cracks, or other imperfections that could cause poor terminal contact. Visually inspect the component side connector to ensure that all of the terminals are uniform and free of damage or deformation. |
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Insert the appropriate adapter from the on the flat wire harness connector in order to test the circuit in question. |
Control Module/Component Voltage and Grounds |
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Test all control module voltage supply circuits. Many vehicles have multiple circuits supplying voltage to a control module. Other components in the system may have separate voltage supply circuits that may also need to be tested. Check the connections on the links and fuses for the modules/components, and other intermediate connections between the voltage source and the module/component. A voltage can be indicated using a test lamp or a multimeter, but it is not possible to test that the circuit can handle a sufficiently high current. Ensure that the circuit can carry the current necessary to operate the component. Refer to Circuit Testing and Power Distribution Schematics. |
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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. Refer to Circuit Testing and Ground Distribution Schematics. |
Temperature Sensitivity |
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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. |
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Freeze Frame, Failure Records, Snapshot, or Vehicle Data Recorder data may help with this type of intermittent condition, where applicable. |
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If the intermittent is related to heat, review the data for a relationship with the following: |
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High ambient temperatures |
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Underhood/engine generated heat |
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Circuit generated heat due to a poor connection, or high electrical load |
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Higher than normal load conditions, towing, etc. |
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If the intermittent is related to cold, review the data for the following: |
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Low ambient temperatures-In extremely low temperatures, ice may form in a connection or component. Inspect for water intrusion. |
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The condition only occurs on a cold start. |
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The condition goes away when the vehicle warms up. |
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Information from the customer may help to determine if the trouble follows a pattern that is temperature related. |
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If temperature is suspected of causing an intermittent fault condition, attempt to duplicate the condition. Refer to Inducing Intermittent Fault Conditions in order to duplicate the conditions required. |
Electromagnetic Interference (EMI) and Electrical Noise |
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A misrouted harness that is too close to high voltage/high current devices such as secondary ignition components, motors, generator etc-These components may induce electrical noise on a circuit that could interfere with normal circuit operation. |
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Electrical system interference caused by a malfunctioning relay, or a control module driven solenoid or switch-These conditions can cause a sharp electrical surge. Normally, the condition will occur when the malfunctioning component is operating. |
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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 interference while in use, but do not fail when the accessories are not in use. Refer to Checking Aftermarket Accessories. |
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Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode. |
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The generator may be allowing AC noise into the electrical system. |
Incorrect Control Module |
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There are only a few situations where reprogramming a control module is appropriate: |
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A new service control module is installed. |
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A control module from another vehicle is installed. |
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Revised software/calibration files have been released for this vehicle. |
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Make sure the control module is programmed with the correct software/is correctly calibrated. If a defective program is detected then the unit must be reprogrammed with the latest software/calibration. See Control unit references regarding replacement, installation and programming. |