Testing for Intermittent Conditions and Poor Connections
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Testing for Intermittent Conditions and Poor Connections
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Special Tools
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J 35616 GM-Approved Terminal Test Kit
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J-38125 Terminal Repair Kit
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When the condition is not currently present, but is indicated in DTC history, the cause may be intermittent. An intermittent may also be the cause when there is a customer complaint, but the symptom cannot be duplicated. Refer to the Symptom Table of the system that is suspect of causing the condition before trying to locate an intermittent condition.
Most intermittent conditions are caused by faulty electrical connections or wiring. Inspect for the following items:
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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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Testing for Terminal Fretting
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Some intermittent conditions can be caused by wire terminal fretting corrosion. Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can pile up enough at the electrical contact spots that the electrical resistance across the connection increases. Movement between the contacting surfaces as small as 10 to 100 microns can cause fretting. To put this in perspective, a sheet of paper is about 100 microns thick, so fretting motion is small and hard to see. Vibration and thermal expansion/contraction are the main sources that create fretting motion. Since vehicles vibrate and can experience large temperature swings, they are a good source for fretting motion. Tin, copper, nickel, and iron surfaces are all susceptible to fretting corrosion. Fretting corrosion can be difficult to see but it looks like small, dark smudges on the terminals contact surface.
To correct a fretting condition disconnect the suspect connector and add Nyogel lubricant 760G (dielectric grease) to both sides of the connector terminals. Then reconnect the connector and wipe away any excess lubricant. This will correct the additional terminal contact resistance due to the terminal fretting corrosion.
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Testing for Proper Terminal Contact
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It is important to test terminal contact at the component and any inline connectors before replacing a suspect component. Mating terminals must be inspected to ensure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation.
Contamination may be caused by the connector halves being improperly connected. A missing or damaged connector seal, damage to the connector itself, or exposing the terminals to moisture and dirt can also cause contamination. Contamination, usually in the underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit.
Deformation is caused by probing the mating side of a connector terminal without the proper adapter. Always use the J 35616 when probing connectors. Other causes of terminal deformation are improperly joining the connector halves, or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact causing an open or intermittently open circuit.
Testing for Proper Terminal Contact in Bussed Electrical Centers (BEC)
It is very important to use the correct test adapter when testing for proper terminal contact of fuses and relays in a bussed electrical center (BEC). Use J-35616-35 to test for proper terminal contact. Failure to use J-35616-35 can result in improper diagnosis of the BEC.
Follow the procedure below in order to test 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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Flat Wire (Dock and Lock) Connectors
There are no serviceable parts for flat wire (dock and lock) connectors on the harness side or the component side.
Follow the procedure below in order to test terminal contact:
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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.
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Control Module/Component Voltage and Grounds
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Poor voltage or ground connections can cause widely varying symptoms.
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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
.
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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.
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Electromagnetic Interference (EMI) and Electrical Noise
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Some electrical components/circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Inspect for the following conditions:
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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.
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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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Note
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DO NOT re-program the control module with the SAME software/calibration files that are already present in the control module. This is not an effective repair for any type of concern.
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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.
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