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

TROUBLE CODE DIAGNOSTICS - 7.4L MPI

Code 51 (1 of 1): Calibration Memory Failure (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 EFI.
DIAGNOSTIC AIDS:
If DTC 51 failed more than once, but is intermittent, replace the ECM.
TEST DESCRIPTION:
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-68
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ACTION
Was the "On-Board Diagnostic" (OBD) System
Check Performed?
1. Clear trouble code 51.
2. Ignition "ON".
Is trouble code reset?
Replace faulty ECM and verify trouble code 51
does not reset.
SERVICE MANUAL NUMBER 23
72801
VALUE YES NO
PROCEED TO
Go to
OBD
– Step 2
System
Check
Refer to
Diag- Diag
nostic nostic
– Step 3
Aids
Verify
–
Repair
90-861326--1 MARCH 1999
–