Diagnostic Information

The diagnostic trouble tree charts and functional checks are designed to locate a faulty circuit or component through logic based on the process of elimination. The charts are prepared with the requirement that the vehicle functioned correctly a, the time of assembly and that there are no multiple failures. Trouble tree charts are designed to be used only when a diagnostic trouble code is active.
The PCM/TCM performs self-diagnostics of powertrain control functions. The PCM/TCM communicates faults with a system of Diagnostic Trouble Codes (DTCs). These DTCs may or may not turn On the MIL (SERVICE ENGINE SOON) or SERVICE lamp to alert the driver.