mojo0104 Posted October 19, 2008 Report Share Posted October 19, 2008 cam position sensor and long term memory module are the codes which come up, causing the service engine soon light to stay on. how do i reset the codes and what is the long term memory module? i have replaced the cam position sensor Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted October 20, 2008 Report Share Posted October 20, 2008 You can clear codes in the onboard diagnostics, but often the systems are designed to clear codes after a certain number of successes. You did not mention which memory reset code you are getting, but either will clear after 40 starts with no current problem. The CAM current probably will clear after 3 successful trips. DTC P0603 Control Module Long Term Memory Reset Circuit Description The PCM has a memory area where it stores certain data it needs to save when the key is turned OFF. This area is called Keep Alive Memory. This diagnostic test monitors the PCMs keep alive memory for a loss or unintended change of data. If such a condition occurs, DTC P0603 will set. Conditions for Running the DTC Test continuously. Conditions for Setting the DTC Keep alive memory checksum does not match previous checksum. Action Taken When the DTC Sets Clear all keep alive memory locations. * The Malfunction Indicator Lamp (MIL) will not illuminate. * No message will be displayed. Conditions for Clearing the DTC * A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. * A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. * Use a scan tool to clear DTCs. * Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. Diagnostic Aids If the battery has been disconnected for any reason DTC P0603 will set. The PCM keeps a running check on the memory; if memory changes it resets. An intermittent loss of power or ground to the PCM will cause a reset. DTC P1621 Control Module Long Term Memory Performance Circuit Description The PCM contains a data storage unit which can save critical data even when battery power is removed. This unit, the Electrically Erasable Programmable Read Only Memory (EEPROM), is used by the PCM to store TP Sensor/Idle Learned values, Transaxle Adapt values and Transaxle Oil Life Index. The EEPROM has several locations available to store this information. If the PCM detects a problem in one location of the EEPROM, it will store the data in another location. If the PCM runs out of good locations in the EEPROM to store data, it will set DTC P1621. The PCM stores the same data in its Keep Alive Memory so that even if the EEPROM is bad and DTC P1621 sets, the operator will not notice any difference in vehicle operation. Even after a DTC P1621 is set, the PCM will continue to look for good locations in the EEPROM in which to store data and if it finds good locations, DTC P1621 will become a history DTC. The EEPROM is soldered into the PCM and cannot be serviced separately. If a current DTC P1621 is set, the PCM must be replaced. Conditions for Running the DTC Tested always. Conditions for Setting the DTC A failure to store data in all EEPROM locations has occurred. Action Taken When the DTC Sets * The Malfunction Indicator Lamp (MIL) will not illuminate. * No message will be displayed. Conditions for Clearing the DTC * A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. * A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. * Use a scan tool to clear DTCs. * Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. Test Description Number(s) below refer to the step number(s) on the Diagnostic Table. 2. If DTC P1621 is set current, the PCM cannot find another location to store the data, so the PCM must be replaced. 3. Cycle the ignition to give the PCM a chance to find a place to store the data. If the DTC resets, no place can be found so the PCM must be replaced. Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
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