6E-66 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Does it rely on some mechanical/vacuum
device to operate?
Physical:
Where are the circuit components (componen
t
locators and wire harness routing diagrams):
Are there areas where wires could be
chafed or pinched (brackets or frames)?
Are there areas subjected to extreme
temperatures?
Are there areas subjected to vibration or
movement (engine, transmission or
suspension)?
Are there areas exposed to moisture, road
salt or other corrosives (battery acid, oil o
r
other fluids)?
Are there common mounting areas with
other systems/components?
Have previous repairs been performed to
wiring, connectors, components or mounting
areas (causing pinched wires between panels
and drivetrain or suspension components
without causing and immediate problem)?
Does the vehicle have aftermarket or dealer-
installed equipment (radios, telephone, etc.)
Step 2: Isolate the problem
At this point, you should have a good idea of what could
cause the present condition, as well as could not cause
the condition. Actions to take include the following:
Divide (and separate, where possible) the system
or circuit into smaller sections
Confine the problem to a smaller area of the
vehicle (start with main harness connections while
removing panels and trim as necessary in order to
eliminate large vehicle sections from furthe
r
investigation)
For two or more circuits that do not share a
common power or ground, concentrate on areas
where harnesses are routed together o
r
connectors are shared (refer to the following hints)
Hints
Though the symptoms may vary, basic electrical failures
are generally caused by:
Loose connections:
Open/high resistance in terminals, splices,
connectors or grounds
Incorrect connector/harness routing (usually in
new vehicles or after a repair has been made):
Open/high resistance in terminals, splices,
connectors of grounds
Corrosion and wire damage:
Open/high resistance in terminals, splices,
connectors of grounds
Component failure:
Opens/short and high resistance in relays,
modules, switches or loads
Aftermarket equipment affecting normal operation
of other systems You may isolate circuits by:
Unplugging connectors or removing a fuse to
separate one part of the circuit from another part
Operating shared circuits and eliminating those
that function normally from the suspect circuit
If only one component fails to operate, begin
testing at the component
If a number of components do no operate, begin
tests at the area of commonality (such as powe
r
sources, ground circuits, switches or majo
r
connectors)
What resources you should use
Whenever appropriate, you should use the following
resources to assist in the diagnostic process:
Service manual
Technical equipment (for data analysis)
Experience
Technical Assistance
Circuit testing tools
5d. Intermittent Diagnosis
By definition, an intermittent problem is one that does
not occur continuously and will occur when certain
conditions are met. All these conditions, however, may
not be obvious or currently known. Generally,
intermittents are caused by:
Faulty electrical connections and wiring
Malfunctioning components (such as sticking
relays, solenoids, etc.)
EMI/RFI (Electromagnetic/radio frequency
interference)
Aftermarket equipment
Intermittent diagnosis requires careful analysis of
suspected systems to help prevent replacing good
parts. This may involve using creativity and ingenuity to
interpret customer complaints and simulating all
external and internal system conditions to duplicate the
problem.
