Mercury MerCruiser MCM 454 Mag MPI Service Manual page 713

TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
Code 42 (3 of 3): Ignition Control (IC) Circuit (Non-Scan) (Continued)
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Index
Page 5F-16
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1. Ignition OFF.
2 Di t ECM J1
2. Disconnect ECM J1 and J2 connectors.
3 Ignition ON 3. Ignition ON.
4. Use DVOM with selector in the OHMS U O
range.
5. Probe ECM harness connector CKT 423 5 P b ECM h
with DVOM to ground. t O to g ou d
It should read more than 3000 Ohms. Does it?
Probe ECM harness connector CKT 424 with a
test light connected to battery positive (B+). test light connected to battery ositive (B+).
Is test light on?
Open CKT 423, faulty connection or faulty igni-
tion module.
With Ohmmeter connected to ECM harness
CKT 423 and ground (–), probe harness CKT
424 with test light connected to battery positive
(B+). (B+).
As test light contacts CKT 424, resistance
should change from over 3000 Ohms to under
1000 Ohms. Does it?
Disconnect distributor 4-way connector. Con-
nect Ohmmeter between CKT 423 and ground
(–). ( ).
Resistance should have gone high (open cir-
cuit). Does it?
Reconnect ECM and idle engine for 1 minute
or until code 42 sets. Does Code 42 Set?
CKT 424 open, faulty connections, or faulty
ignition module.
CKT 423 shorted to ground.
Faulty ECM.
Code 42 is intermittent. Refer to "Diagnostic
Aids."
Disconnect ignition module 4-way connector.
Is test light on?
CKT 424 shorted to ground.
Faulty ignition module.
d J2 t
O S
t CKT 423
SERVICE MANUAL NUMBER 23
– – Ste 4 Step 4 Ste 5 Step 5
– – Step 13 Ste 13 Step 6 Ste 6
– – –
– – Ste 8 Step 8 Step 7 Ste 7
– – Ste 9 Step 9 Ste 10 Step 10
– Step 11 Step 12
– – –
– – –
– – –
– – –
– – Step 14 Ste 14 Ste 15 Step 15
– – –
– – –
90-861326--1 MARCH 1999