feed, be it power or ground. If a main relay is used and the trans is
stuck in 2nd or 3rd gear, then this circuit is the first place to look.
(Input Speed Sensor) or OSS (Output Speed Sensor)
The ISS (Input Speed Sensor), OSS (Output Speed Sensor) and the
VSS (Vehicle Speed Sensor) for the M5HA/M5DA can be either a 2 or a
3 wire unit. The 2 wire unit are magneting sensors. These can be
tested with an Ohm meter. Normal resistances for this sensor range
between 200 to 600 Ohms. The resistance value is not as important as
the signal amplitude produced. The amplitude can be affected by
corrossion around the sensor mounting, creating excessive air gap
between sensor and relluctor wheel. If a 3 wire unit is used, then a
square wave is always produced. These units signal the TCM with an
ON and OFF signal (square wave). The 3 wire ISS/OSS/WSS also
called a Hall-Effect or Magneto-Resistive sensor is not affected by
speed probems. These units should always have POWER (6 to 12
volts), GROUND and SIGNAL (5 to 12 volts). The sensor simply toggles
the signal voltage to ground as the relluctor wheel speeds up. The TCM
compares input shaft speed to final output speed. It then compares
the speed differential to a series of look-up table to determine if the
trans is slipping (code issued).
Transmission Temperature Sensor
The Transmission Temperature Sensor for the M5HA/M5DA is a
negative temp. coefficient. This means that as transmission fluid
temperature goes up, then the voltage output goes down. The TCM
provides a 5.00 volt reference on one wire and a ground on the other
(always 2 wires). Double check and make sure that there's ground and
5 volts with KOEO and the trans-temp sensor DISCONNECTED. A test
light can be used to look for ground. A multimeter has to be used to
look for the 5 volt reference.
This book is based on the "Automotive Transmission Troubleshooter" software by the
same author. All similarities to this software package are intended. Both of these
products are copyrighted by the author, Mandy Concepcion. For further insight on
automotive transmissions please see our complementary DVD-Video.