Testing for Intermittent Conditions and Poor Connections
Special Tools
EL-35616 Terminal Test Probe Kit
For equivalent regional tools, refer to Special Tools .
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:
| • | Wiring broken inside the insulation |
| • | Poor connection between the male and female terminal at a connector |
| • | Poor terminal to wire connection - Some conditions that fall under this description are poor crimps, poor soldered joints, crimping over the wire insulation rather than the wire itself, and corrosion in the wire to terminal contact area, etc. |
| • | 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. |
| • | 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. |
| • | Wiring that comes in contact with hot or exhaust components |
Testing for Terminal Fretting
Some intermittent conditions can be caused by wire terminal fretting corrosion. Fretting corrosion is a build-up of insulating, oxidised wear debris that can form when there is a small motion between electrical contacts. The oxidised 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.
Testing for Proper Terminal Contact
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 EL-35616 kit 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 tab, can result in poor terminal contact causing an open or intermittently open circuit.
Testing for Proper Terminal Contact in Bussed Electrical Centres
It is very important to use the correct test adapter when testing for proper terminal contact of fuses and relays in a bussed electrical centre. Use the EL-35616 kit to test for proper terminal contact. Failure to use the EL-35616 kit can result in improper diagnosis of the bussed electrical centre.
Follow the procedure below in order to test terminal contact:
- Separate the connector halves.
- 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 underbonnet or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals, and connector body.
- Using an equivalent male terminal/terminated lead, verify that the retention force is significantly different between a known good terminal and the suspect terminal. Replace the female terminal in question.
Flat Wire Connectors
There are no serviceable parts for flat wire connectors on the harness side or the component side.
Follow the procedure below in order to test terminal contact:
- Remove the component in question.
- 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.
- 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.
- Insert the appropriate adaptor into the flat wire harness connector in order to test the circuit in question.
Control Module/Component Voltage and Grounds
Poor voltage or ground connections can cause widely varying symptoms.
| • | 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. Inspect connections at the module/component connectors, fuses, and any intermediate connections between the voltage source and the module/component. A test lamp or a DMM may indicate that voltage is present, but neither tests the ability of the circuit to carry sufficient current. Operate the component to test the ability of the circuit to carry sufficient current. Refer to Circuit Testing and Power Distribution Schematics . |
| • | 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. Operate the component to test the ability of the circuit to carry sufficient current. Refer to Circuit Testing and Ground Distribution Schematics . |
Temperature Sensitivity
| • | 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. |
| • | Freeze Frame, Failure Records, Snapshot, or Vehicle Data Recorder data may help with this type of intermittent condition, where applicable. |
| • | If the intermittent is related to heat, review the data for a relationship with the following: |
| - | High ambient temperatures |
| - | Underbonnet/engine generated heat |
| - | Circuit generated heat due to a poor connection, or high electrical load |
| - | Higher than normal load conditions, towing, etc. |
| • | If the intermittent is related to cold, review the data for the following: |
| - | Low ambient temperatures - In extremely low temperatures, ice may form in a connection or component. Inspect for water intrusion. |
| - | The condition only occurs on a cold start. |
| - | The condition goes away when the vehicle warms up. |
| • | Information from the customer may help to determine if the trouble follows a pattern that is temperature related. |
| • | 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 and Electrical Noise
Some electrical components/circuits are sensitive to electromagnetic interference or other types of electrical noise. Inspect for the following conditions:
| • | A mis-routed harness that is too close to high voltage/high current devices such as secondary ignition components, motors, alternator 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 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. |
| • | Improper installation of non-factory or aftermarket add on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, mobile phones, etc. - These accessories may create interference in other circuits while operating and the interference would disappear when the accessory is not operating. Refer to Checking Aftermarket Accessories . |
| • | Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode. |
| • | The generator may be allowing AC noise into the electrical system. |
Incorrect Control Module
| • | There are only a few situations where reprogramming a control module is appropriate: |
| - | A new service control module is installed. |
| - | A control module from another vehicle is installed. |
| - | Revised software/calibration files have been released for this vehicle. |
| | Note: 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. |
| • | Verify that the control module contains the correct software/calibration. If incorrect programming is found, reprogramme the control module with the most current software/calibration. Refer to Control Module References for replacement, setup, and programming. |
| © Copyright Chevrolet. All rights reserved |
| © Copyright Chevrolet. All rights reserved |
