V-BELT SET 9Y0291 - Caterpillar

Each circuit component in the engine electronics system is monitored by the Electronic Control Module (ECM) for abnormal operation. The ECM is capable of recognizing several abnormal conditions and selecting an appropriate reaction.When an abnormal condition is recognized by the ECM, an ACTIVE Diagnostic Code is generated. The ECM will first communicate the condition to the operator. This communication may include lighting a diagnostic lamp or displaying the diagnostic condition on a display panel.The reaction of the ECM to an ACTIVE diagnostic code will seldom affect more than engine performance. Much of the data that is received from the circuit components by the ECM is used in order to control engine function. If a component that provides this type of data has an ACTIVE diagnostic condition, the data cannot be used. If a diagnostic code becomes ACTIVE, the ECM will flag suspect data as "INVALID DATA". A default value that has been predetermined will be used for the engine control that is associated with that component. The operation of the subsystem will continue, and the engine will continue to run. However, loss of an electronic component that causes an ACTIVE diagnostic code may cause an engine shutdown.ACTIVE diagnostic codes can indicate problems that are as minor as a loose connection. ACTIVE diagnostic codes can also indicate larger problems that may be associated with the deterioration of a component. Any condition that causes an ACTIVE diagnostic code should be investigated immediately. If an ACTIVE diagnostic code is present during normal engine operation, the engine should be serviced immediately by a qualified technician.