SERVICE MANUAL NUMBER 23
TROUBLE CODE DIAGNOSTICS - 7.4L MPI
Code 44 (1 of 3): Knock Sensor (KS) Circuit (Scan) - No Knock Detected
FUSE 15A
b
a
e
485
GRN
PUR
c
d
a - Knock Sensor Module
b - To System Relay
c - Starboard Knock Sensor
d - Port Knock Sensor
e - Knock Sensor Signal
CIRCUIT DESCRIPTION:
Knock Sensor (KS) system circuit is accomplished with a module that sends a voltagesignal
to the ECM. As the knock sensor detects engine knock, the voltage from the KS module to
the ECM drops, and this signals the ECM to start retarding timing. The ECM will retard timing
when knock is detected and RPM or engine coolant temperature is above a certain value.
DIAGNOSTIC AIDS:
Check for the following conditions:
•
Poor connection at ECM. Inspect harness connectors for backed out terminals,
improper mating, broken locks, improperly formed or damaged terminals, and poor ter-
minal to wire connection.
•
Damaged harness. Inspect the wiring harness for damage.
After repairs, clear DTC’s following “Clearing Trouble Codes” procedure at the front of this
section. Failure to do so may result in DTC’s not properly being cleared.
NOTE: if fuel octane is too high, a false DTC 44 may be set.
90-861326--1
MARCH 1999
Page 5G-65
| 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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