Mercury MerCruiser MCM 454 Mag MPI Service Manual page 775

TROUBLE CODE DIAGNOSTICS - 7.4L MPI
Code 42 (3 of 3): Ignition Control (IC) Circuit (Non-Scan) - Grounded IC Circuit,
Open Bypass Circuit, or Grounded Bypass Circuit
STEP
3
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7
8
9
10
11
12
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Index
Page 5G-30
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ACTION
1. Ignition "OFF."
2. Disconnect ECM harness connectors.
3. Using a DVOM set on OHMS, probe
ECM harness terminal J2-23 to ground.
Is resistance within specified value?
1. Leave DVOM connected from ECM har-
ness terminal J2-23 to ground.
2. Using a test light connected to battery
positive (B+), probe ECM harness terminal
J2-24.
3. As the test light contacts J2-24, the resis-
tance should switch from 3000 Ohms to under
1000 Ohms.
Does the resistance switch to under the
specified value?
Using a test light connected to battery positive
(B+), probe ECM harness terminal J2-24
(CKT424).
Does light illuminate?
Disconnect ignition module 4-way connector.
Does test light illuminate?
1. Reconnect ECM.
2 Start engine and idle for 2 minutes or Ma- 2. Start engine and idle for 2 minutes or Ma-
rine Diagnostic Code Tool indicates a stored
trouble code trouble code.
Is 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 CKT 424. If a problem
is found, repair as necessary. 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" on facing page. Check harness
and connectors 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
3000 to
6000
Ohms
Step 4 Step 8
1000
Ohms
Step 7 Step 5
– Step 6 Step 9
– Step 10 Step 11
– Step 12 Step 13
– Step 11
– Step 11
Verify Verify
Repair
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90-861326--1 MARCH 1999
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