Important Preliminary Checks Before Starting
Perform the
Engine Controls Schematics
before using the symptom tables. Verify that all of the following conditions are true:
| • | The engine control module (ECM) and the malfunction indicator lamp (MIL)
are operating correctly. |
| • | There are no diagnostic trouble codes (DTCs) stored. |
| • | The scan tool data is within the normal operating range. Refer to . |
| • | Verify the customer concern and locate the correct symptom listed below.
Inspect items indicated under that symptom. |
| • | Several of the symptom procedures direct the technician to perform a visual/physical
inspection. This important step can lead the technician to the cause of the problem
without further checks and can save valuable time. |
| • | Verify the correct installation and operation of electronic options, such
as lights and cellular phones. |
Diagnostic Trouble Code Tables
Do not use the diagnostic trouble code (DTC) tables to try to correct an intermittent
fault. The fault must be present to locate the problem. Incorrect use of the DTC tables
may result in the unnecessary replacement of parts.
Faulty Electrical Connections or Wiring
Most intermittent problems are caused by faulty electrical connections or wiring.
Perform a careful inspection of suspect circuits for the following:
| • | Poor mating of the connector halves |
| • | Terminals not fully seated in the connector body |
| • | Improperly formed or damaged terminals - All connector terminals
in a problem circuit should be carefully inspected, reformed, or replaced to insure
contact tension. |
| • | Poor terminal-to-wire connection - This requires removing the terminal
from the connector body. |
| • | Use the following tables when diagnosing a symptom concern: |
