- When to Use This Section
PURPOSEDiagnosis By Symptom is designed to help diagnose powertrain symptoms.
BEFORE STARTING
Diagnosis By Symptom should only be used when directed to by the Powertrain System Check or diagnosis in another powertrain section. The Powertrain System Check must always be performed first. Failure to follow these guidelines may result in incorrect or unnecessary diagnosis. Testing and Inspection
POWERTRAIN SYSTEM CHECK FIRST
Performing the Powertrain System Check first may lead to a code trouble tree or some other easily diagnosed problem. If no other clues to the root cause of a customer complaint are apparent, the Powertrain System Check will refer to the charts in this section which indicate what subsystems and components should be checked. These charts are not meant to be component replacement lists. Each subsystem or component should be checked for proper operation and repaired or replaced only if they are not operating properly.
SYMPTOM SELECTION
If directed to this section from the Powertrain System Check or diagnosis in another section, select the symptom with the description that best fits the customer complaint. Then begin performing the tests suggested and proceed until the root cause is found. The suggested tests are generally listed in order of probability and/or ease of diagnosis. The tests need not be performed in the listed order, though. If you have already performed one of the tests listed, there is no need to perform it a second time.
When referred to diagnosis in another section, perform the test listed and if the test does not lead to a problem, return to this section and continue where you left off.
VISUAL CHECK
Several of the symptom procedures call for a careful check. This check should include:
^ Vacuum hoses for splits, kinks, and improper connections. as shown on Emission Control Information label.
^ Air leaks at throttle body mounting and intake manifold.
^ Ignition wires for cracking, hardness, and improper routing.
^ Wiring for improper connections, pinches, and cuts.
The importance of performing the visual check cannot be stressed too strongly -- it can lead to correcting a problem without further checks and can save valuable time.