JLG 450A II Series, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3-144 – JLG Lift – 3121290
DTC 604- Microprocessor Failure - RAM
• Engine Control Module- Random Access Memory.
• Check Condition- Key on.
• Fault Condition- Internal ECM microprocessor memory
access failure.
• Corrective Action(s)- Illuminate MIL and/or sound audible
warning or illuminate secondary warning lamp, disable
adaptive fueling correction for remainder of key cycle, rec-
ommend power derate 2 and low rev limit to reduce possi-
ble engine damage and/or overspeed condition.
• Non-emissions related fault
Random Access Memory is located in the microprocessor and
can be read or written at any time. Data stored in RAM include
DTCs (when fault configuration is set to “Battery Power
Retained"), adaptive fuel learn tables, octane adaptation table,
misfire adaptation tables, and closed loop fuel multipliers. The
ECM has checks that must be satisfied each time an instruction
is executed.
This fault sets if the ECM detects a problem accessing or writ-
ing information to RAM and should be configured to set a
power derate 2 and low rev limit to reduce possible engine
damage and reduce possibility of an overspeed condition. If
this fault sets, the ECM will reset itself and log the code. This
fault should be erased by a technician after diagnostics are
performed. The fault should be configured to never forget and
will not self-erase.