Mercury MerCruiser MCM 454 Mag MPI Service Manual page 812

SERVICE MANUAL NUMBER 23
Code 44 (3 of 3): Knock Sensor (KS) Circuit (Scan) - No Knock Detected
Index
90-861326--1 MARCH 1999
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STEP
5. Using a test light connected to battery
positive (B+), repeatedly touch knock sensor
harness terminal (CKT 496).
Does the voltage value change?
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 the 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
8
check for abnormal mechanical engine noises.
If OK, replace faulty knock sensor.
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
11
connectors.
2. Using a DVOM, measure the resistance
of each sensor from the sensor terminal to
ground.
Is the resistance of each sensor within the
specified value?
12 Replace faulty KS sensor. Is action complete?
13 Replace faulty KS module. Is action complete?
Repair faulty ECM connections or replace
14
faulty ECM. Is action complete?
DTC 44 is intermittent. Locate and repair inter-
15
mittent faulty connections. Refer to "Diagnostic
Aids."
ACTION
TROUBLE CODE DIAGNOSTICS - 7.4L MPI
VALUE YES
PROCEED TO
– Step14
– Step 6
– Step 10
–
Verify
–
Repair
–
–
7600 to
Step 15
8800
Ohms
–
–
Verify
–
Repair
–
Page 5G-67
NO
Step 5
Step 9
Step 13
Step 11
–
–
–
Step 12
–
–
–
–