TROUBLE CODE DIAGNOSTICS - 7.4L MPI
SERVICE MANUAL NUMBER 23
Code 44 (2 of 3): Knock Sensor (KS) Circuit (Scan) - No Knock Detected
TEST DESCRIPTION:
Step 2. This step ensures the knock sensor circuitry is within the proper resistance
value.
Step 3. Applying 12 volts with a test light to CKT 496 simulates a signal from the knock
sensor. The knock sensor is faulty if a response occurs.
Step 4. This step confirms the ability of the KS module to remove the voltage from the
signal line when it detects spark knock. Since the knock sensor produces an AC voltage
signal, it may be necessary to repeatedly touch (tickle) the harness connector with the
test light to simulate this type of signal.
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.
Step6.ThisstepdeterminesitCKT485isshortedtovoltageoriftheKSmoduleisfaulty.
STEP
ACTION
VALUE
YES
NO
PROCEED TO
Go to
Was the “On-Board Diagnostic” (OBD) System
Check Performed?
OBD
System
Check
1
2
–
Step 2
1.
Disconnect 5-wire knock sensor (KS)
module harness connector.
3500
4700
Ohms
to
2.
Connect DVOM from KS module harness
terminal “E” (CKT 496) to a known good
ground near the knock sensor.
Is resistance between the specified value?
Step 3
Step 7
1.
tor.
Reconnect KS module harness connec-
3
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+), repeatedly touch knock sensor
harness terminal (CKT 496).
Does a noticeable drop in RPM occur, or
using a timing light, does the timing re-
tard?
–
Step 8
Step 4
4
1. Ignition “OFF.”
2.
3.
Disconnect ECM J1 connector.
Connect DVOM from ECM harness ter-
minal J1-1 (CKT 485) to a known good ground.
You should see 8-10 volts.
4.
Allow DVOM voltage to stabilize.
Page 5G-66
90-861326--1 MARCH 1999
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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