Important Preliminary Checks
Checks
| Action
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Before Using This Section
| Before using this section, you
should have performed the Powertrain On-Board Diagnostic System Check. Several
of the following symptom procedures call for a careful visual and
physical check. The visual and physical checks are very important.
These checks can lead to correcting a problem which may save valuable
time.
|
Visual and Physical Checks
|
| • | Check the VCM grounds for being clean, tight and in their proper
location. Refer to VCM Description. |
| • | Check the vacuum hoses for splits, kinks and proper connections,
as shown on the Vehicle Emission Control Information label. |
| • | Check thoroughly for any type of leak or restriction. |
| • | Check for air leaks at all the mounting areas of the intake manifold
sealing surfaces. |
| • | Check the ignition wires for the following conditions: |
| • | Check the wiring for the following items: |
| • | The following symptom tables contain groups of possible causes
for each symptom and cover several engines. The following symptom tables cover
several engines. The order of these procedures is not important.
If the scan tool readings do not indicate the problems, then proceed
in a logical order, easiest to check or most likely to cause first.
In order to determine if a specific vehicle is using a particular
system or component, refer to the Control Module Wiring Diagrams
for an application. |
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Symptom
|
- Verify the customer complaint.
- Locate the correct symptom table.
- Check the items indicated under that symptom.
Use the following tables when diagnosing a symptom complaint.
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Intermittents
Checks
| Action
|
Definition: The problem may or
may not turn ON the Malfunction Indicator Lamp (MIL) or store a Diagnostic
Trouble Code (DTC).
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Preliminary Checks
|
| • | Refer to Important Preliminary Checks. |
| • | Do not use the DTC tables. If a fault is an intermittent, the
use of DTC tables may result in the replacement of good parts. |
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Damaged Electrical Connections or Wiring
| Carefully reform all the connector terminals in the problem
circuit in order to ensure the proper contact tension. If necessary replace
all the connector terminals in the problem circuit in order to ensure
the proper contact tension.
An intermittent may be caused by a poor connection, rubbed through wire
insulation, or a broken wire inside the insulation.
Thoroughly check any circuitry that is suspected of causing the intermittent
complaint for the following conditions:
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wire connections |
| • | Physical damage to the wiring harness |
| • | Moisture in the connector |
|
Road Test
| If a visual and physical check does not locate the cause of the problem, drive
the vehicle with a J 39200
DMM connected to a suspected circuit or use a scan tool.
When the problem occurs, an abnormal voltage or scan reading indicates
the problem may be in that circuit.
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Intermittent Components
| The following components can cause
an intermittent:
| • | A defective relay, Control Module driven solenoid, or a switch
that can cause an electrical system interference. Normally, the problem will
occur when the faulty component is operating. |
| • | The improper installation of electrical devices, such as lights,
2-way radios, electric motors, etc. |
| • | Route the Ignition Control (IC) wires away from the spark plug
wires, ignition system components and the generator. The wire for the engine
ground from the Control Module to the ignition system should be a
good ground. |
| • | The ignition secondary voltage shorted to a ground. |
| • | The Malfunction Indicator Lamp (MIL) circuit or the Diagnostic
Test Terminal intermittently shorted to a ground. |
| • | The Control Module grounds. |
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Loss of DTC Memory
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- In order to check for the loss of the DTC Memory, disconnect the
Throttle Position (TP) sensor.
- Idle the engine until the Malfunction Indicator Lamp illuminates.
- The VCM should store a Throttle Position DTC.
- The Throttle Position DTC should remain in the memory when turning
off the ignition.
- If the Throttle Position DTC does not store and remain, the Control
Module is damaged.
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Additional Checks
| Check for an open diode across the A/C compressor clutch and for other
open diodes. Refer to the Wiring Diagrams.
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