Checking for intermittent faults and poor contact in the connectors
If the fault is not currently present, but is logged in the DTC log, the cause may be intermittent. An intermittent problem can also be a problem that the customer complains about, but its symptoms cannot be reproduced. Before looking for the cause of an intermittent fault, it is necessary to review the symptom table of the system in which the cause of the fault is suspected. Most intermittent faults are caused by poor contact in electrical connectors or wiring. Inspect for the following defects:
- Wire break inside the insulation
- Contact failure between pin and socket contacts of the connector
- Broken connection between terminal and wire - may be poor crimping, soldering, crimping over insulation instead of wire, as well as corrosion in the contact area between terminal and wire, etc.
- Punctured or damaged insulation can let moisture in, causing corrosion. The conductor may corrode inside the insulation, without visible signs. Inspect for swollen and hard sections of wires in the circuits of the suspected malfunction.
- Pinched, broken wiring, or frayed insulation can cause an intermittent short-open when the exposed conductor touches another wire or parts of the vehicle.
- Wiring in contact with hot parts or exhaust system.
- Restore intermittent fault conditions to reproduce the fault situation to confirm the customer's complaint.
- Perform the intermittent electrical fault tests described in the test procedures to look for intermittent opens, high resistances, shorts to ground, and shorts to power.
- Run the Advanced Intermittent Fault Diagnosis using the scan tool and vehicle data recorder screen capture.
Checking the reliability of contact between the terminals
Before replacing a supposedly defective device, it is necessary to check the contact between the terminals of the connectors on the device itself and in the intermediate connections. It is necessary to inspect the mating parts of the connectors to make sure that there is a reliable contact between the terminals. The contact between the male and female terminals of the connector may be broken due to contamination or deformation.
Contamination can occur due to improper connection of mating connectors. Missing or damaged seals, damage to the connector itself, or moisture or dirt ingress can also lead to contamination. Contamination, commonly found on underhood and underbody connectors, leads to corrosion of the terminals, which can result in permanent or intermittent open circuits.
Deformation can be caused by test leads connected to a connector pin without an appropriate adapter. Other reasons for the deformation of the terminals may be incorrect connection of the mating parts of the connector or their repeated connection and disconnection. Deformation, usually of the contact shank of a female terminal, can lead to a broken contact and, accordingly, a permanent or intermittent open 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 56 series, perform the following procedure.
Perform the following procedure to check contact between connector pins:
- Disconnect mating connectors.
- Visually verify that there is no contamination of the mating parts of the connector. Contamination may appear as white or green deposits inside the connector housing or between the pins. This results in increased lead resistance, intermittent contact, or an open circuit. The connector under the hood or under the bottom with traces of contamination must be replaced as an assembly, including all terminals, seals and the connector housing.
- Using the pin equivalent of j-38125, check if the holding force differs greatly between the good pin and the suspect pin. Replace the defective socket terminal.
Outputs for supply voltage and ground of the controller/device
Defects in the supply voltage wires and ground connection can lead to a wide variety of malfunctions.
- Check all power supply circuits of the controller. Many vehicles have multiple controller power circuits. Some devices in the system may have separate power circuits, which should also be checked. Inspect the 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 tests show the circuit's ability to carry sufficient current. Verify that the circuit can carry the current required to operate the device.
- Check all ground connections on the controller and ground circuits in the system. The controller may have multiple ground circuits. Some devices in the system may have separate ground connections, which should also be checked. Make sure that the ground connections are clean and that the connections at the ground point are secure. Inspect the connections on the device and in the connection blocks where they are used. Verify that the circuit can carry the current required to operate the device.
Temperature effect
- An intermittent fault may occur when the device/connector reaches normal operating temperature. A malfunction may occur when the device/connector is cold or vice versa hot.
- Freeze frame, fault records, screen capture and vehicle data recorder data can assist in locating an intermittent fault where possible.
- If the intermittent fault is related to heat, view data related to the following factors:
- high outside temperature;
- heat generation under the hood / in the engine;
- heat generated in electrical circuits due to contact failure or high load;
- increased load compared to normal, towing, etc.
If the intermittent fault is related to cold, view the following data:
- Low Ambient Temperature - Ice can form in connectors and devices at very low temperatures. Inspect for moisture ingress;
- the malfunction occurs only during a cold start;
- the malfunction disappears when the car warms up;
- increased load compared to normal, towing, etc.
Information from the customer may be useful in determining if the failure conditions are temperature dependent.
If temperature is suspected to be a factor in the occurrence of a malfunction, 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.
- Incorrectly routed wiring harness too close to high voltage/high current devices, motors, generators, etc. - these devices may induce electrical noise in circuits, which may interfere with the functioning of these circuits.
- Interference in electrical systems caused by faulty relays, electromagnets and switches controlled by controllers - under these conditions, sudden voltage surges can occur. Typically, these conditions occur when a malfunctioning device is running.
- Improper installation of 3rd party or aftermarket accessories - lights, radios, amplifiers, electric motors, remote starters, alarm devices, cell phones, etc. - These devices may cause interference when in use, but do not interfere when switched off.
- Check for an open diode at the A/C compressor clutch terminals and other faulty diodes. Some relays can be fitted with clamping diodes.
- The generator may introduce AC noise into the electrical system.
Wrong controller
- Occasionally there are situations when reprogramming of the controller is required.
- A new service controller has been installed.
- Installed controller from another car.
- New software or calibration files have been released for this vehicle.
Important: Do not load into the controller software/calibration files similar to those already loaded into the controller. This is not an effective method for fixing any problem.
Verify that the correct software/calibration is in the controller. If incorrect software is found, download the latest software/calibration to the controller. Refer to the appropriate controller section for replacement, setup, and programming procedures.
Diagnostic check after repair
1. Reinstall all devices and connectors that were removed or replaced during the diagnostics.
2. Perform the adjustment, programming, or adjustment procedures necessary when replacing or removing a device or controller.
3. Delete trouble codes.
4. Switch off the ignition for 60 seconds.
5. If repair was related to DTCs, restore DTC conditions and use freeze frame/fault recordings (if possible), to make sure that DTCs are not generated again. If the DTC recurs or another DTC occurs, perform the appropriate diagnostic procedure for that DTC. If the repair was symptomatic, recreate the conditions under which the customer experienced the problem to ensure that the repair was successful. If the customer's problem recurs, return to the affected vehicle and perform appropriate symptom diagnosis.
A new service controller has been installed.
Installed controller from another car.
New software or calibration files have been released for this vehicle.
Important: Do not load into the controller software/calibration files similar to those already loaded into the controller. This is not an effective method for fixing any problem.
Verify that the correct software/calibration is in the controller. If incorrect software is found, download the latest software/calibration to the controller. Refer to the appropriate controller section for replacement, setup, and programming procedures.