Mercury MerCruiser MCM 454 Mag MPI Service Manual page 780

SERVICE MANUAL NUMBER 23
Code 44 (3 of 3): Knock Sensor (KS) Circuit (Non-Scan) - No Knock Detected
Index
90-861326--1 MARCH 1999
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STEP
1. Disconnect KS module 5-wire harness
5
connector.
2. Using a test light connected to battery
positive (B+), probe KS module harness termi-
nal "D" (CKT 486).
Does test light illuminate?
Using a test light connected to ground, probe
6
KS module harness terminal "C" (CKT 485).
Does test light illuminate?
Locate and repair open or short to ground in
7
CKT 496. If a problem is found, repair as nec-
essary. Was a problem found?
Inspect knock sensor terminal contacts. Also
check for abnormal mechanical engine noises.
8
If OK, replace faulty knock sensor. Is action
complete?
Locate and repair open in ground CKT 486. Is
9
action complete?
10 Replace faulty KS module. Is action complete?
1. Disconnect both knock sensor electrical
connectors.
2. Using a DVOM, measure the resistance
11
of each sensor from the sensor terminal to
ground. Is the resistance of each sensor within
the specified value?
Replace faulty knock sensor. Is action com-
12
plete?
13 Replace faulty KS module. Is action complete?
Repair faulty ECM connections or replace
14
faulty ECM. Is action complete?
Trouble code is intermittent. Locate and repair
15
intermittent faulty connections. Refer to "Diag-
nostic Aids."
ACTION
TROUBLE CODE DIAGNOSTICS - 7.4L MPI
VALUE YES
PROCEED TO
– Step 6
Step 10
–
Verify
–
Repair
–
–
7600 to
8800
Ohms
Step 15
–
–
Verify
–
Repair
–
Page 5G-35
NO
Step 9
Step 13
Step 11
–
–
–
Step 12
–
–
–
–