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 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. |
• |
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,
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.
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 kitwhen 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
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. Use the EL-35616 kitto test for
proper terminal contact. Failure to use the EL-35616
kitcan result in improper diagnosis of the bussed electrical
center.
Follow the procedure below in order to test terminal
contact:
1. |
Separate the connector
halves. |
2. |
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. |
3. |
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:
1. |
Remove the component in
question. |
2. |
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. |
3. |
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.
|
4. |
Insert the appropriate adapter
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 |
|
- |
Underhood/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, generator 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, cell 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, reprogram the control module with the most current
software/calibration. Refer to
Control Module References for replacement, setup, and
programming. |
|