Allison B 300, Руководство по устранению неисправностей

Страница: 11 / 396

Copyright © 1998 General Motors Corp. 1–5
GENERAL DESCRIPTION
W T E C I I E L E C T RO N I C C O N T RO L S T RO U B L E S H O OT I N G M A N UA L
1–4. THROTTLE POSITION SENSOR (Figure 1–7)
The Throttle Position Sensor (TPS) can be mounted to the engine, chassis, or transmission. The TPS contains a pull
actuation cable and a potentiometer. One end of the cable is attached to the engine fuel lever and the other, inside a
protective housing, to the TPS potentiometer. Output voltage from the TPS is directed to the ECU through the
external harness. The voltage signal indicates the throttle position and, in combination with other input data,
determines shift timing.
Figure 1–7. Throttle Position Sensor
1–5. SPEED SENSORS (Figure 1–8)
Three speed sensors — engine speed, turbine speed, and output speed — provide information to the ECU. The
engine speed signal is generated by ribs on the shell of the torque converter pump. The turbine speed signal is
generated by the rotating-clutch housing spline contours. The output speed signal is generated by a toothed
member attached to the output shaft (except for the MD 3070, where the toothed member is the transfer case idler
gear). The speed ratios between the various speed sensors allow the ECU to determine if the transmission is in the
selected range. Speed sensor information is also used to control the timing of clutch apply pressures, resulting in
the smoothest shifts possible. Hydraulic problems are detected by comparing the speed sensor information for the
current range to that range’s speed sensor information stored in the ECU memory.
Figure 1–8. Speed Sensors
C
B
A
V00628
THROTTLE POSITION SENSOR
ENGINE
(EXTERNAL)
HD/B 500
TURBINE
(EXTERNAL)
OUTPUT
(EXTERNAL)
V03470
MD/B 300/B 400
TURBINE
(INTERNAL)
MD/B 300/B 400
RETARDER OUTPUT
(EXTERNAL)
MD 3070PT
OUTPUT
(INTERNAL)