Checking Leads And Connectors

CHECKING LEADS
Many electrical system faults are caused by faulty leads and bad connections. These faults arise mainly through interference from other electrical systems. or from mechanical or chemical damage.





Check Connections Visually
In all measurements and checks where a connector is taken apart, contacts should be checked visually.

Checks:
^ Look for oxidation which can affect contacts in connectors.
^ Make sure that male connectors are intact and that copper leads are securely connected to pins.





Breaks
Breaks in leads can be detected by loss of function. Frayed and worn leads which have come loose are common fault sources.

Check:
^ Disconnect connectors at both ends of lead.
^ Take measurements with ohmmeter between ends of lead.

Ohmmeter should read approx. 0 ohms for unbroken lead.

Check Intermittent Break:
^ Check lead visually.
^ Gently shake lead and pull on connections during measurement to locate damage.





Short Circuit to Ground
Short circuit between a live lead and ground usually causes a blown fuse or loss of function when lead is powered.

Check:
^ Activate all switches and sensors in circuit and check if fuse blows.
^ Disconnect connectors to circuit components so that measurements are not affected.





^ Connect an ohmmeter between lead and ground.

Ohmmeter should read infinite resistance if no components are connected.

Check Intermittent Short Circuit to Ground:
^ Check lead visually.
^ Gently shake lead and pull on connections during measurement to locate damage.





Short Circuit to Live
Short circuit between a lead and live usually causes a blown fuse or loss of function when lead is powered.

Check:
^ Connect a voltmeter across various points in circuit while operating switches and sensors.
^ Voltmeter reading depends on circuit being checked and status of switches and sensors.
^ Use wiring diagram to determine correct circuit voltage.





^ Connect an ohmmeter between suspect leads to detect short circuits between them.

Ohmmeter should read infinite resistance between leads which are not interconnected.

Check Intermittent Short Circuit to Live:
^ Check lead visually.
^ Gently shake lead and pull on connections during measurement to locate damage.





Bad Contact (connections)
Bad contact in connections is caused by oxidation on pins and contacts or bad contact with leads. Bad contact gives the same fault as an intermittent break in a lead.

Check:
^ Check connections visually.
^ Gently shake lead and pull on connections during measurement to locate damage.
^ Always check that ECM and ECM box contacts have no bent or damaged pins or sockets which could cause faults.

Contact Resistance and Oxidation
Resistance in contacts, leads and connections should be virtually 0 ohm. However, a certain resistance will arise due to oxidation in connections.

If resistance becomes too great, functions will be affected. The degree of resistance necessary to cause interference depends on circuit loading. but is generally a few ohms

Check:
^ Check connections visually.





Cleaning of Male and Female Contacts

NOTE: Releasing agents must not be used on HO2S connector.

^ Ignition off.
^ Disconnect battery negative pole.
^ Spray releasing agent P/N 1161435-1 on the open connector.
^ Blow with compressed air.





Greasing Female Contacts

NOTE: Do not fill casing with grease.

^ Pump grease P/N 1161417-9 into female contact directly from tube.
^ Check all contact cavities are filled.





^ Use a single male pin to check that there is good contact in the female connector and that pin remains in position when pulled gently.