Diagnosing electrical wiring faults (Chevrolet Captiva 1)

Checking for intermittent faults and contact problems in connectors

If the fault is not present but is recorded in the fault code log, the cause may be intermittent. An intermittent fault may also be a fault that the customer is complaining about, but the symptoms cannot be reproduced. Before looking for the cause of an intermittent fault, it is necessary to review the fault symptom table of the system in which the fault is suspected. Most intermittent faults are caused by poor connections in electrical connectors or wiring. Inspect for the following defects:

• Wire break inside insulation
• Contact failure between the pin and socket contacts of the connector
• A faulty connection between the contact and the wire - this may be due to poor crimping, soldering, crimping over the insulation instead of the wire, as well as corrosion in the contact area between the terminal and the wire, etc.
• Punctured or damaged insulation can allow moisture to pass through, causing corrosion. The conductor may corrode within the insulation without any visible signs. Inspect for swollen or stiff sections of wire in the suspected fault circuit.
• Pinched, broken wiring, or frayed insulation can cause intermittent short-open conditions when the exposed conductor touches another wire or vehicle parts.
• Wiring in contact with hot parts or the exhaust system.
• Recreate the intermittent fault conditions to reproduce the fault situation to confirm the customer complaint.
• Perform the intermittent electrical fault tests described in the test procedures to find intermittent opens, high resistance points, shorts to ground, and shorts to supply voltage.
• Perform an advanced diagnostic procedure for intermittent faults using a scan tool screenshot and vehicle data recorder.

Checking the reliability of contact between terminals

Before replacing a suspected faulty device, it is necessary to check the contact between the connector pins on the device itself and in the intermediate connections. It is necessary to inspect the mating parts of the connectors to ensure that there is reliable contact between the pins. Contact between the pin and socket pins of the connector may be disrupted due to contamination or deformation.

Contamination can occur due to improper mating of the connector parts. Missing or damaged seals, damage to the connector itself, or exposure to moisture or dirt can also cause contamination. Contamination, commonly found on underhood and underbody connectors, can cause corrosion of the terminals, which can result in permanent or intermittent open circuits.

Deformation can be caused by measuring probes connected to the connector terminal without a corresponding adapter. Other causes of terminal deformation can be incorrect connection of the mating parts of the connector or their repeated connection and disconnection. Deformation, usually of the contact tail of the female terminal, can lead to contact failure and, accordingly, to a permanent or intermittent break in the circuit.

Round electrical connectors

It is very important to check the contact between the connector pins on the device, as well as in the intermediate connectors. To check the contact in the connectors "metri-pack" or series 56 perform the following procedure.

Perform the following procedure to check the contact between the connector terminals:

• Disconnect the mating parts of the connector.
• Visually check for contamination of the mating parts of the connector. Contamination may appear as a white or green coating inside the connector body or between the terminals. This leads to increased resistance of the terminals, intermittent contact or open circuit. The connector under the hood or under the bottom with traces of contamination should be replaced as an assembly, including all terminals, seals and connector body.
• Using a male terminal equivalent from j-38125, check whether the holding force is significantly different between the good terminal and the terminal with the suspected fault. Replace the faulty female terminal.

Controller/device supply voltage and ground terminals

Defects in the supply voltage wires and ground connections can lead to a wide variety of malfunctions.

• Check all power supply circuits to the controller. Many vehicles have multiple power supply circuits to the controller. Some devices in the system may have separate power supply circuits that should also be checked. Inspect connections at the controller/device connectors, fuses, and all intermediate connections between the voltage source and the controller/device. A test light or digital multimeter may indicate the presence of voltage, but no test will indicate the ability of the circuit to carry enough current. Verify that the circuit can carry the current needed to operate the device.
• Check all ground connections at the controller and ground circuits in the system. There may be more than one ground circuit on the controller. Some devices in the system may have separate ground connections that should also be checked. Make sure the ground connections are clean and the connections at the ground point are secure. Inspect the connections at the device and at the terminal blocks where they are used. Make sure the circuit can carry the current required to operate the device.

Effect of temperature

• An intermittent fault may occur when the device/connector reaches normal operating temperature. The fault may occur when the device/connector is cold or when it is hot.
• Freeze frame, fault records, screen shot and vehicle data recorder data can assist in locating the intermittent fault where possible.
• If the intermittent fault is related to heat, review data related to the following factors:
• high outside temperature;
• heat generation under the hood/in the engine;
• heat generated in electrical circuits due to poor contact or high load;
• increased load compared to normal, towing, etc.

If the intermittent fault is related to cold, review the following data:

• low ambient temperature -- ice may form in connectors and devices in very low temperatures. Inspect for moisture;
• the malfunction occurs only during cold start;
• the fault disappears when the car warms up;
• increased load compared to normal, towing, etc.

Information from the customer may be useful in determining if the fault conditions are temperature dependent.

If temperature is suspected of influencing the occurrence of a fault, an attempt should be made to recreate these conditions.

Electromagnetic Interference (EMI) and Electrical Noise

Some electrical devices/circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Check for the following conditions.

• An improperly routed wiring harness that is too close to high voltage/high current devices, motors, generators, etc. - these devices can induce electrical noise into the circuits, which can cause the circuits to malfunction.
• Electrical disturbances caused by faulty relays, solenoids, and switches controlled by controllers - these conditions can cause sudden voltage spikes. These conditions typically occur when a faulty device is operating.
• Improper installation of third party or aftermarket accessories - lights, radios, amplifiers, electric motors, remote starters, alarms, cell phones, etc. - these devices may interfere when in use, but do not interfere when turned off.
• Check for a diode break on the terminals of the air conditioner compressor clutch and other faulty diodes. Some relays may have limiting diodes.
• The generator can induce AC noise into the electrical system.

Inappropriate controller

• Occasionally, situations arise where reprogramming of the controller is required.
• New service controller installed.
• A controller from another car was installed.
• New software or calibration files have been released for this vehicle.

Important: Do not load software/calibration files into the controller that are identical to those already loaded into the controller. This is not an effective method of troubleshooting any problem.

Ensure that the controller has the correct software/calibration. If incorrect software is found, load the latest software/calibration into the controller. Refer to the relevant controller section for replacement, setup and programming procedures.

Diagnostic check after repair

1. Reinstall all devices and connectors that were removed or replaced during diagnostics.

2. Perform adjustment, programming, or setup procedures required when replacing or removing a device or controller.

3. Clear fault codes.

4. Turn off the ignition for 60 seconds.

5. If the repair was associated with the issuance of fault codes, restore the conditions for issuing fault codes and use freeze frame/fault records (if possible), to ensure that the fault codes do not reoccur. If the fault code recurs or another fault code appears, perform the diagnostic procedure for that fault code. If the repair was symptom-related, recreate the conditions under which the customer's problem occurred to ensure that the repair was successful. If the customer's problem reoccurs, return to the affected vehicle and perform the appropriate symptom-related diagnostic.



New service controller installed.

A controller from another car was installed.

New software or calibration files have been released for this vehicle.

Important: Do not load software/calibration files into the controller that are identical to those already loaded into the controller. This is not an effective method of troubleshooting any problem.

Ensure that the controller has the correct software/calibration. If incorrect software is found, load the latest software/calibration into the controller. Refer to the relevant controller section for replacement, setup and programming procedures.

(The article is reprinted from the website CHEVYMAN.RU)