Diagnostic Aids

Do not clear DTCs unless directed by procedure. Clearing DTCs will erase all freeze frame and failure records stored in PCM memory. Poor engine performance can sometimes be diagnosed as a rear axle driveability condition. In order to avoid mis-diagnosis of rear axle, always perform engine controls diagnostic system check. Use a scan tool that is known to function correctly. If necessary, test scan tool on another vehicle. Ensure scan tool contains most current file available. Scan tool will display a loss of communication error message under following conditions: PCM power is interrupted. Ignition switch is turned to OFF position. Battery voltage level is very low. A poor connection at data link connector.