Mercury MerCruiser D2.8L D-Tronic Service Manual page 491

SERVICE MANUAL NUMBER 22
THROTTLE POSITION (TP) SENSOR
The Throttle Position (TP) Sensor is a potentiometer connected to the throttle cable. The
TP has one end connected to 5 volts from the ECM and the other to ECM ground. A third
wire is connected to the ECM to measure the voltage from the TP. As the throttle cable is
operated, the angle of the wiper inside the TP body is changed: the voltage output of the
TP also changes. At a closed throttle position, the voltage output of the TP is low
(approximately .4 volt). As the throttle position changes the output increases, so that at wide
open throttle (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).
Failures that might occur with the TP sensor, are:
•
TP sensor out of range (SRC High or Low).
•
Low idle switch defective.
•
TP sensor supply voltage incorrect.
•
Plausibility (possibility of error) between TP sensor and low idle switch signal to the
ECM.
If the TP circuit is open, the ECM will set a Code P1515. If the TP circuit is shorted, the ECM
will think the vessel is at WOT, and a trouble Code P1515 will be set. A problem in any of
the TP circuits will set a Code P1515. Once a trouble code is set, the ECM will use a default
value resulting in an engine speed of 800 rpm.
90-860074--1 FEBRUARY 2002
a
a - TP Sensor
b - Electrical Connector
DESCRIPTION
b
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