Mercury MerCruiser MCM 454 Mag MPI Service Manual page 720

SERVICE MANUAL NUMBER 23
Code 21 (1 of 3): Throttle Position (TP) Sensor Circuit (Scan)
CIRCUIT DESCRIPTION:
The Throttle Position (TP) Sensor provides a voltage signal that changes as throttle blades
open or close. Signal voltage should vary from about .7 volts at idle to about 4.5 volts at Wide
Open Throttle (W.O.T.).
The TP signal is one of the most important inputs used by the Electronic Control Module
(ECM) for fuel control and for most of the ECM controlled outputs.
DIAGNOSTIC AIDS:
The scan tool reads throttle position in voltage and percentage of throttle blade opening.
With ignition ON or at idle, TP signal voltage should read between .3 and .8 volt with the
throttle closed, and increase at a steady rate as throttle is moved toward Wide Open Throttle
(W.O.T.).
If Code 23 is also set, check CKT 813 for faulty wiring or connections. Check terminals at
sensor for good contact.
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" at the front of this section. Failure to do so may result in codes not properly being
cleared.
Index
90-861326--1 MARCH 1999
Downloaded from https://needmanual.com/
b
i
B
a
C
C
h
A
A
a - Throttle Position Sensor
b - Front View Of Connector
c - To IAT Sensor
d - To Map Sensor
e - Sensor Ground
f - TP Signal
g - 5V Reference
h - Wide Open Throttle
i - Idle
TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
c
B
d
e
f
g
Page 5F-23