Diagnostics are performed by the ECM continuously to detect out of range rationality and system faults.
During the time that the key is ON, if an input signal is out of range, meaning the signal is either greater or lesser than what the signal range should be during normal operation, the ECM will record a fault. It will also monitor the operation of systems and will determine if they are working within a normal operational range (rationality fault detection). If the ECM detects that a system falls outside a predetermined range, it will record and set a fault code.
During normal engine operation, the ECM automatically performs several tests to detect faults. When it has detected a fault, the ECM often invokes a fault management strategy to allow continued, though sometimes degraded, vehicle operation.
The ECM can also set codes associated with the injection control system on a continuous basis that is an improvement from previous systems in which specific diagnostic tests had to be performed in order to get the codes.
A Fault is an indication of a malfunction measured or monitored electronically. Sometimes faults are referred to as Codes.
Codes are three digit numbers assigned to faults to indicate the source of the malfunction. Most codes will indicate the source and the Mode of failure. The Failure Mode will indicate the signal reading, i.e. out of range high, out of range low, or in range fault.
With the engine running, the ECM memory will also record Event Engine Hours. This feature records if the engine has been operated beyond maximum r/min, overheated (coolant temperature), low on coolant, or experienced low oil pressure.
The standard Engine Events are overspeed (Over RPM) of the engine and excessive coolant temperature. Low oil pressure and low coolant level operation will also be monitored and recorded as Event Engine Hours, if the engine is equipped with the optional engine warning/shutdown system.
Engine events logged into the ECM memory are permanent and can be retrieved with the Electronic Service Tool (EST).
| Series 40E Troubleshooting Manual – 6SE241 |
| Generated on 10-13-2008 |