SERVICE MANUAL NUMBER 23
TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
Code 43 (1 of 3): Knock Sensor (Ks) Circuit (Non-Scan)
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:
The ability to sense engine knock or detonation is accomplished with a module that sends
a voltage signal 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 retard timing.
DIAGNOSTIC AIDS:
If CKT 496 is routed too close to secondary ignition wires, the KS module may see the inter-
ference as a knock signal, resulting in false retard.
An intermittent problem may be caused by a poor or corroded connection, rubbed through
wire connection, a wire that is broken inside the insulation, or a corroded wire.
Any circuitry that is suspected as causing the intermittent complaint should be thoroughly
checked for backed-out terminals, improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wiring connections, corroded terminals and/or wiring,
or physical damage to the wiring harness. After repairs, clear codes following “Clearing
Codes” procedure at the front of this section. Failure to do so may result in codes not
properly being cleared.
TEST DESCRIPTION:
Number(s) below refer to step number(s) on the diagnostic table.
Step 2. This step ensures that 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 checks if a voltage signal from the KS module is present at the ECM.
Index
90-861326--1
MARCH 1999
Page 5F-17
| 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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