Continuous Self Test Description

PURPOSE
The Continuous Self Test detects powertrain control system failures contributing to driveablity or emission concerns. The Continuous Self Test is always active. Unlike the Key On Engine Off (KOEO) and Key On Engine Running (KOER) Self Tests, that can only be activated on-demand. The technician retrieves the Diagnostic Trouble Code (DTC) stored in continuous memory as part of the Quick Test.

OPERATION
When the Continuous Self Test detects a fault, a DTC is stored in the Powertrain Control Module (PCM) memory. The stored DTC can be retrieved at a later time, even if the fault no longer exists. This capability makes the continuous self test valuable when diagnosing intermittent faults.

During Pinpoint testing, the technician may perform a specific Drive Cycle before running Quick Test. This is necessary to detect certain faults not tested during KOEO or KOER Self Tests. When using the New Generation STAR (NGS) tester or equivalent scan tool, it is possible to select "Retrieve Continuous Codes" in both the Diagnostic Data Link and generic menu.

In the On-Board Diagnostics II (OBD II) functions menu, only the Malfunction Indicator Lamp (MIL) DTC's are "Output". MIL DTC's activate the "Check Engine" light in the instrument panel and are only generated for faults with the emission controls. Typically, non-MIL DTC's are for controls other than the emission system (i.e., Air Conditioning Cycling Switch (ACCS) or Manual Lever Position sensor (MLP) faults).

Any scan tool that meets OBD II requirements can access Continuous Memory to retrieve MIL DTCs. However, when performing KOEO or KOER Self-Test or retrieving all Continuous DTCs, (MIL and non-MIL) with a generic scan tool, it will take additional manually entered command strings. All self-tests are menu driven with the NGS scan tool.

During most of the diagnostic procedures, it is required that all DTCs be retrieved. It is necessary to use either the NGS Diagnostic Data Link Menu or the Enhanced Diagnostic Mode in the generic scan tool.