Mercury MerCruiser MCM 454 Mag MPI Service Manual page 807

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