Mercury MerCruiser MCM 454 Mag MPI Service Manual page 779

TROUBLE CODE DIAGNOSTICS - 7.4L MPI
Code 44 (2 of 3): Knock Sensor (KS) Circuit (Non-Scan) - No Knock Detected
TEST DESCRIPTION: (CONTINUED)
Step 5. This step checks the ground circuit from the KS module. If the test light is dim,
check ground CKT 486 for excessive resistance.
Step 6. This step determines if CKT 485 is shorted to voltage or if the KS module is faulty.
STEP
1
2
3
4
Index
Page 5G-34
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ACTION
Was the "On-Board Diagnostic" (OBD) System
Check Performed?
1. Disconnect the 5 wire Knock sensor (KS)
module harness connector.
2. Connect DVOM from KS module harness
terminal "E" (CKT496) to a known good ground
near the knock sensor.
Is resistance between the specified value?
1. Reconnect KS module harness connec-
tor.
2. Disconnect knock sensor harness con-
nector.
3. Start engine.
4. Hold engine speed steady above 2500
RPM.
5. Using a test light connected to battery
positive (B+), repeated touch knock sensor
harness terminal (CKT 496).
Does the RPM drop occur, or using a timing
light, does the timing retard?
1. Ignition "OFF".
2. Disconnect ECM J1 connector.
3. Connect DVOM from ECM harness ter-
minal J1-1 (CKT485) to a known good ground.
It should be 8-10 volts.
4. Allow voltage to stabilize.
5. Using a test light connected to battery
positive (B+), repeatedly touch knock sensor
harness terminal (CKT 496).
Does the voltage value change?
SERVICE MANUAL NUMBER 23
VALUE YES NO
PROCEED TO
Go to
OBD
– Step 2
System
Check
3500 to
4700
Ohms
Step 3 Step 7
– Step 8 Step 4
– Step 14 Step 5
90-861326--1 MARCH 1999