Tp (Throttle Position) Sensor / Low Idle Switch - Mercury MerCruiser D2.8L D-Tronic Service Manual

EDI DIAGNOSIS

TP (Throttle Position) Sensor / Low Idle Switch

Scan Code:
Blink Code:
Malfunction Indicator Lamp:
CIRCUIT DESCRIPTION:
The TP (Throttle Position) sensor translates throttle position into a voltage signal. The TP
sensor is basically a linear potentiometer. The ECM supplies 5 volts to the sensor and
processes a returning voltage signal for operation of the fuel timing solenoid valve. The TP
output voltage will vary through the range from idle to WOT. Also at closed throttle the Low
Idle Switch (sometimes referred to as LGS) is activated. This confirms to the ECM that the
TP is at the closed throttle position. As the throttle position changes the output increases,
so that at WOT, the output voltage should be near 4.5 volts. By monitoring the output voltage
from the TP sensor, the ECM can determine fuel delivery based on the throttle position
(operator demand).
If the TP circuit is open, the ECM will set a Scan Code P1515. If the TP circuit is shorted,
the ECM will think the vessel is at WOT, and this code will be set. A problem in any of the
TP circuits (e. g. Low Idle Switch) will set this same code. Once this trouble code is set, the
ECM will use a default value for TP signal.
15
57
55
65
1
Page 5E-40
a
7
6
1
5
2
4
3
b
a - TP Sensor
b - Harness Connector
c - TP Sensor Signal
d - 5 Volt Reference Signal
e - Sensor Ground (–)
f - Battery Supply Voltage
g - To MAP/IAT Sensor
CKT PIN
TP Sensor Signal
5 Volt Reference Signal
Sensor Ground (–)
Low Idle Switch (LGS)
ECM / Battery Ground (–)
P1515
1144
ON
b
ORN/WHT
PNK/YEL
BLU/WHT
BRN/RED
g
NAME
SERVICE MANUAL NUMBER 22
ECM
c
15
d
57
e
55
f
65
BLK
1
75565
90-860074--1 FEBRUARY 2002