Mercury MerCruiser MCM 454 Mag MPI Service Manual page 809

TROUBLE CODE DIAGNOSTICS - 7.4L MPI
Code 43 (2 of 2): Knock Sensor (KS) Circuit (Scan) - Continuous Knock
Detected
STEP
1
2
3
4
5
6
7
8
9
Index
Page 5G-64
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ACTION
Was the "On-Board Diagnostic" (OBD) System
Check Performed?
1. Disconnect 5-wire knock sensor (KS)
module harness connector
2. Ignition "ON," engine "OFF."
3. Using a test light connected to ground,
probe KS module harness terminal "B" (CKT
439).
Does test light illuminate?
Using a test light connected to battery positive
(B+), probe KS module harness terminal "D"
(CKT 486).
Does test light illuminate?
1. Ignition "OFF."
2. Reconnect KS module harness connec-
tor.
3. Disconnect J1 connector.
4. Ignition "ON," engine "OFF."
5. Connect DVOM from ECM harness ter-
minal J1-1 (CKT 485) to a known good ground.
Is the voltage within the specified value?
Locate and repair open or short to ground in
CKT 439. Is action complete?
Locate and repair open in CKT 486. Is action
complete?
Locate and repair open or short to ground in
CKT 485. If a problem is found, repair as nec-
essary. Was a problem found?
Replace faulty KS module. Is action complete?
Repair faulty ECM connections or replace
faulty ECM. Is action complete?
SERVICE MANUAL NUMBER 23
VALUE YES NO
PROCEED TO
Go to
OBD
– Step 2
System
Check
– Step 3 Step 5
– Step 4 Step 6
8-10
Volts
Step 9 Step 7
–
–
Verify
– Step 8
Repair
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90-861326--1 MARCH 1999
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