TRANSMISSION AND TORQUE CONVERTER CD3340B/YB4411
7-20
Published 04/07/2015 Control # 569-00
Checking Parking Brake Switch
The correct operation of the parking brake can be checked
using either of the following tests:
1. Check continuity between pin 8 and ground (pin 11 or
12) when parking brake is applied.
2. Connect a test lamp between pin 23 or 24 and pin 8.
The lamp will illuminate when the parking brake is
applied.
Checking Sensor Operation
Machines equipped with a transmission ECU have a speed
sensor installed (Figure 7-11). The sensor detects the speed
of rotation of the output shaft for the transfer gear and sends
this information to the ECU.
The ECU requires a speed signal to determine the operating
speed of the machine. Some gear selections will not be
permitted if the speed signal is too high (i.e. downshifts).
NOTE: The ECU is designed to inhibit 4th gear selection if
the speed sensor fails to send a signal.
A test lamp should be used to check operation of the speed
sensor, as follows:
1. Park the crane on a firm, level ground. Engage the
parking brake and set the forward/reverse lever to the
neutral position.
2. Turn off the engine and remove the ignition key.
3. Disconnect the speed sensor from the wire harness.
4. Remove the speed sensor from the transmission. Place
a suitable container underneath to catch the oil.
5. Check that the sensor is working by connecting a volt/
ohm meter to the pins in the speed sensor connector
and checking the voltage reading. Connect the positive
(+) meter lead to the pin for the RED wire and the
negative (-) meter lead to the pin for the BLUE wire.
Move a piece of metal in front of sensor. When the metal
passes the front of the sensor, the meter should be
registering 12 VDC. If it does not register 12 VDC,
replace the speed sensor.
6. While the sensor is removed, check the sensor for
damage.
7. If the sensor is working properly, the problem is most
likely in the harness itself. Repair or replace the harness.
Speed Sensor Depth
The speed sensor depth is not adjustable and is set at time
of manufacturing during case machining.
Tips on Common Problems
ECU Mounting
If the ECU mounting capscrews are overtightened the ECU
and internal components can be damaged. Hand tighten the
capscrews only.
Speed Sensors
Generally speed sensors do not fail. Most problems seen are
caused by physical damage due to transit, installation or
faulty wiring.
Occasionally sensors are out of tolerance or installed
incorrectly.
Harnesses
By far the most troublesome cause of ECU inoperative is the
wire harnesses. The integrity of the electrical connectors and
components is paramount to problem free operation.
It has been noticed that water entry into the shift control
assembly can occur if the control is damaged (replace the
control). This is particularly important on open cab cranes. It
is possible that the water can short internal switches
providing false signals to the ECU. If water is trapped in the
control it can corrode internal switch contacts making them
stick on or off.
Moisture or contamination trapped in connectors is a
probable cause of many faults.
However effective an electrical connector, it can not be
expected to sustain direct steam cleaning using high
pressure hoses. It is recommended that operators should
make themselves aware of connectors which are vulnerable
to a direct jet from a steam cleaner and avoid continued
contact.
Poor ground of electrical components can cause problems.
Check that the grounding to the ECU, shift control and other
switches is sound.
No 4th Gear
There are two main causes for this problem:
FIGURE 7-11
Speed Sensor
p0716
Reference Only
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