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?
–
Verify
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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