Continuous Memory Self-Test

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Testing for Continuous Memory DTC's is a functional test of the powertrain control module performed under any condition (engine running or off) with the key on. Unlike the KOEO and KOER self tests, which can only be activated on demand, the Continuous Self Test is always active. A fault does not need to be present at the time of testing for Continuous DTC's and is therefore, especially valuable when diagnosing intermittent faults. This test will detect failures contributing to driveability or emission concerns. The vehicle may need to be driven or the OBDII Drive Cycle completed to allow the PCM to detect a fault. Refer to DRIVE CYCLES for more information. When a fault is stored in memory, a Diagnostic Trouble Code (DTC) will be output on the data link at the end of the test when requested by a scan tool.

There are two types of Continuous DTC's. The first type is an emission related malfunction indicator lamp (MIL) code which will illuminate the CHECK ENGINE or SERVICE ENGINE SOON indicator in the instrument cluster. The second is a non emission related non-MIL code which will never illuminate the cluster indicator.

For emission related MIL codes, the PCM will store the DTC in continuous memory when a fault is detected for the first time. At this point the DTC will not illuminate the MIL and is now considered a pending code. The purpose of pending codes is to assist in repair verification by reporting a pending DTC after one drive cycle. If the same fault is detected after the next ignition start-run cycle, the emission related MIL code will illuminate the MIL. The MIL will remain on even if the fault is intermittent. The MIL will be extinguished if the fault is not present through three consecutive drive cycles or the DTCs are cleared. Also, an emission related pending MIL and non emission related (non-MIL) code will be erased after approximately 40 vehicle warm up cycles or the DTCs are cleared.

Any scan tool that meets OBDII requirements can access Continuous Memory to retrieve emission related MIL DTC's. However, not all scan tools access pending and non emission related (non-MIL) DTC's in the same way.

During most diagnostic procedures in this manual, it is required that all DTC's be retrieved and cleared. Consult the instruction manual from the tool manufacturer for specific instructions.