Code 51 (1 Of 2): Calibration Memory Failure (Non-Scan) - Mercury MerCruiser MCM 454 Mag MPI Service Manual

TROUBLE CODE DIAGNOSTICS - 7.4L MPI

Code 51 (1 of 2): Calibration Memory Failure (Non-Scan)

CIRCUIT DESCRIPTION:
This test allows the ECM to check for a calibration failure by comparing the calibration value
to a known value stored in the EEPROM.
This test is also used as a security measure to prevent improper use of calibrations or
changes to these calibrations that may alter the designed function of the EFI system.
DIAGNOSTIC AIDS:
If DTC 51 failed more than once, but is intermittent, replace the ECM.
TEST DESCRIPTION:
Number(s) below refer to step number(s) on the diagnostic table.
Step 2. This step checks to see if the fault is present during diagnosis. If present, the
ECM is not functioning properly and must be replaced.
STEP
1
2
3
Index
Page 5G-36
Downloaded from https://needmanual.com/
ACTION
Was the "On-Board Diagnostic" (OBD) System
Check Performed?
1. Install Marine Diagnostic Code Tool.
2. Using clear trouble code procedure, clear
trouble code 51.
3. Ignition "ON".
4. Switch Marine Diagnostic Code Tool to
the "Service Mode".
Does trouble code 51 reset?
Replace faulty ECM and verify trouble code
does not reset. Is action complete?
SERVICE MANUAL NUMBER 23
72801
VALUE YES NO
PROCEED TO
Go to
OBD
– Step 2
System
Check
Refer to
Diag- Diag
nostic nostic
Aids
– Step 3
Verify
–
Repair
90-861326--1 MARCH 1999
–