Check Mode
Check mode can be used to increase the ability of the Powertrain Control Module (PCM) to detect engine control system malfunctions. PCM can be requested to operate in CHECK MODE by using OUTPUT CONTROLS feature of the scan tool. While in CHECK MODE operation, PCM will illuminate Malfunction Indicator Light (MIL) and record freeze frame data even on the first failure of a "B" type DTC. Not all engine control system diagnostics will be enhanced by check mode operation. The check mode service bay test can be performed while driving the vehicle to duplicate the customer concern. Those diagnostics most commonly known to benefit from check mode operation will be specified in the diagnostic procedure.
To activate the enhanced diagnostics of check mode operation, perform the following procedure:
- Capture or save any DTC or freeze frame information on the scan tool before entering CHECK MODE operation. All DTC and freeze frame information will be cleared by PCM when CHECK MODE is entered.
- Turn ignition switch to RUN position, engine OFF.
- Using scan tool, enter CHECK MODE operation from SPECIAL FUNCTIONS menu. Verify MIL is flashing which indicates check mode request was received and accepted.
- Return to DATA LIST selection on the scan tool.
- DO NOT turn OFF the ignition after requesting CHECK MODE operation with a scan tool. PCM will return to NORMAL MODE operation when the ignition is cycled from ON to OFF to ON.
- Start engine.
- Operate vehicle within conditions under which the original concern was noted or within freeze frame conditions that set the DTC.
- The DIAGNOSTIC MODE parameter in scan tool data list can be viewed at anytime to verify the vehicle is still operating in CHECK MODE. See SCAN TOOL DATA LIST .
- If MIL illuminates while in check mode, observe and capture all DTC and freeze frame information with the scan tool.
- CHECK MODE operation can be terminated by cycling the ignition switch, or commanding NORMAL MODE with the scan tool.