Mercury MerCruiser MCM 7.4L MPI User Manual

TROUBLE CODE DIAGNOSTICS - 7.4L MPI SERVICE MANUAL NUMBER 23
Page 5G-62 90-861326--1 MARCH 1999
Code 42 (3 of 3): Ignition Control (IC) Circuit (Scan) Grounded IC Circuit, Open
Bypass Circuit, or Grounded Bypass Circuit
STEP ACTION VALUE YES NO
PROCEED TO
5
Using a test light connected to battery positive
(B+), probe ECM harness terminal J2-24 (CKT
424).
Does test light illuminate? – Step 6 Step 9
6
Disconnect the ignition module 4-wire connec-
tor.
Does the test light illuminate? – Step10 Step 11
7 1. Reconnect ECM.
2. Start engine and idle for 2 minutes or
until trouble code 42 sets.
Is trouble code trouble code 42 present? – Step 12 Step 13
8
Locate and repair short to ground in CKT 423.
If a problem is found, repair as necessary.
Was
a problem found?
– Step 11
9
Locate and repair open in CKT 424. Was a
problem found?
–
Verify
Step 11
10
Locate and repair short to ground in CKT 424.
Is action complete?
–
V
er
if
y
Repair
–
11
Replace faulty ignition module. Is action com-
plete?
– –
12
Repair faulty ECM connections or replace
faulty ECM.
Is action complete?
– –
13
Trouble code 42 is intermittent. Refer To “Diag-
nostic Aids” following. Check harness and con-
nectors for an intermittent open or short to
ground in CKT 424, or an intermittent short to
ground in CKT 423.
– – –
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Index

Mercury MerCruiser MCM 7.4L MPI Specifications

General

Brand	Mercury
Model	MerCruiser MCM 7.4L MPI
Category	Engine
Language	English