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WSG-1068 IGNITION SYSTEM
Preliminary Checks
Before using this section verify the customer complaint
and refer to the appropriate symptom chart. Perform the
procedure included in the symptom chart.
Basic Circuit Checks
Basic circuit checks help to minimize pinpoint test steps
by providing a procedure to diagnose harness faults
associated with the Electronic Engine Control (EC)
System. The following techniques provide helpful
reminders for diagnosing open circuits (continuity),
shorts to ground and shorts to power.
NOTE:
The suspect circuit must be isolated before
testing.
When disconnecting any harness connector,
always inspect for damaged or pushed out pins,
corrosion and loose wires. Repair as necessary.
The digital multimeter must be set to the correct
scale.
The techniques do not apply in all situations,
therefore, it is necessary to follow each pinpoint
test step accurately and completely.
General resistance and voltage values are
specified below. Always use the pinpoint test
values if they differ.
Always turn the key to the OFF position unless
directed otherwise by the pinpoint test.
Each of the following procedures will require the Global
Control Platform (GCP) and component to be
disconnected to isolate the harness.
Open Circuit (Continuity)
Disconnect GCP. Measure the harness resistance
between the suspect circuit at the harness connector
and the appropriate GCP harness connector pin. The
resistance must be less than 5.0 ohms.
Shorts to Ground
Measure the harness resistance between the suspect
circuit at the harness connector and a reliable ground
(B+, chassis ground or PWR GND). The resistance must
be greater than 10,000 ohms.
Shorts to Power
Key ON to power up circuit. Measure voltage between
the suspect circuit at the harness connector and a
reliable ground. The voltage must be less than 1.0 volt.
Visual/Physical Check
Several of the symptom procedures call for a careful
visual/ physical check. This can often lead to repairing a
problem without performing unnecessary steps. Use the
following guidelines when performing a visual/physical
check:
Inspect unit for modifications or aftermarket equipment
that can contribute to symptom, verify that all electrical
and mechanical loads or accessory equipment is “OFF’’
or disconnected before performing diagnosis.
Inspect engine fluids for correct levels and evidence
of leaks.
Inspect vacuum hoses for damage, leaks, cracks,
kinks and improper routing, inspect intake manifold
sealing surface for a possible vacuum leak.
Inspect all wires and harnesses for proper
connections and routing, bent or broken connector
pins, burned, chafed, or pinched wires, corrosion, and
verify harness grounds are clean and tight.
Inspect GCP, sensors and actuators for physical
damage.
Inspect fuel system for adequate fuel level, and fuel
quality (concerns such as proper fuel pressure and
contamination).
Inspect intake air system and air filter for restrictions.
Intermittent Problems
Most intermittent problems are caused by faulty
electrical connections or wiring. Perform a careful
visual/physical check for the following conditions:
Poor mating of the connector halves or a
terminal not fully seated in the connector
(backed out).
Improperly formed or damaged terminals.
Improper contact tension. All connector
terminals in the problem circuit should be
carefully checked.
Poor terminal-to-wire connections. This requires
removing the terminal from the connector body
to check.
Improperly installed aftermarket equipment or
accessories.
Operate the engine with accessories “OFF’’ and a
suitable multimeter connected to the suspected circuit.
An abnormal voltage when the malfunction occurs is a
good indication that there is a fault in the circuit being
monitored
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