STEP AS 4V9810 - Caterpillar

Engine: Industrial, Marine, and Generator Set that Use Flash Programming
AllCaterpillar electronic controls have a feature to automatically clear Diagnostic Trouble Codes (DTCs) (diagnostics and events) from the log system if the DTCs are not active within a predetermined period of service meter hours (SMH). The auto clear functionality helps to make sure that the stored DTCs are current enough and ensure that the troubleshooting is still needed. If the DTC is not active in the auto clear time, then the problem may not be still existing. In this case, a technician does not need to spend time to troubleshoot an old problem that has likely already been corrected or is not happening often enough to determine the root cause. All ECUs (a.k.a. ECMs) store only limited number of unique DTCs in the memory. The limit is generally around 30 DTCs (15 diagnostics and 15 events) but vary by flash file. All the parameters of auto clear are fixed in the ECM flash file.The auto clearing functionality is also required to ensure that the memory is not filled up with old data that could prevent new more relevant data from being stored. When memory allocated for logged events is full, a new event will not be stored as logged event. When memory allocated for diagnostics is full, a new logged diagnostic may overwrite existing logged diagnostics based on priority. Some ECM flash file configurations turn off the auto clear feature in order to store only predetermined number of logged DTCs in the ECM. Auto clearing of DTCs is common within our industries and other related industries.Note: For Tier 4 Engines and some Machines the critical DTCs [such as High Engine Coolant Temperature, Engine over speed and low engine oil pressure] will not Auto Clear. The rest of the DTCs will auto clear if the DTC is not active in the auto clear time.Examples of Auto Clear configurations:
Tier 3 Engine ECM (C15, C18, C27 & C32) is configured to delete logged DTCs if the logged DTCs do not become active within 100 SMH. Engine ECM has memory allocated to store up to 15 logged diagnostics and 15 logged events.
Motor Grader (24M) Tier 3 Machine ECM is configured to delete logged diagnostics if the logged diagnostics do not become active within 150 SMH. Events do not auto clear. Machine ECM has memory allocated to store up to 20 logged diagnostics and 20 logged events.
Track-Type Tractors (D10T & D11T) Tier 3 Machine ECM is configured to delete logged DTCs if the logged DTCs do not become active within 150 SMH. Machine ECM has memory allocated to store up to 20 logged diagnostics and 10 logged events.Example Scenario in Tier 3 C15 Engine:
An active "Engine Coolant Temperature Sensor : voltage above normal" diagnostic is deactivated at 700 SHM and stored as logged diagnostic at 700 SHM. The stored diagnostic is automatically cleared from logged diagnostics at 800 SHM, if the diagnostic does not become active between 700 to 800 SMH.Different Methods