TROUBLESHOOTING INSTRUCTIONS (CONT). -726280190

TM 9-2320-364-20-1

2-11. TROUBLESHOOTING INSTRUCTIONS (CONT).

NOTE

In the diagnostic mode, the ATEC ECU update rate is approximately 1 seconds. If

the transmission is shifting rapidly, it is possible that the transmission may pass through

several "attained" ranges more quickly than the readout can display them. This is not a

fault of either the ATEC ECU or the DDR.

(19)

The readout displays the transmission output shaft speed (rpm) when the transmission made its last range

upshift or downshift. Converter lockups are excluded. Due to the slow update rate of the ATEC ECU, be

careful to match the displayed value with the proper shift. If you are not certain, use the transmission

HOLD feature to inhibit unwanted shifts.

(20)

A speed sensor is located on the rear cover of the transmission to detect output shaft rpm. The readout

shows actual transmission output shaft speed in revolutions per minute; the readout lower limit is 60 rpm.

(21)

The readout indicates the transmission output shaft speed (rpm) when the last converter lock-up (engage

or disengage) occurred. When the converter is locked up (engaged), it provides a direct mechanical link

from the engine through the converter. When the converter is not locked (disengaged), the converter

pump and turbine are connected by hydraulic fluid only. Lockup rpm is generally different at closed and

open throttle positions.

(22)

Oil temperature. A temperature sensor is located in the transmission sump on CLT755 transmission. It is

located in the lock-up valve body assembly. High oil temperature may result from overfilling or cooling

system problems. Low oil temperature may result from cold weather conditions. The readout provides

both Fahrenheit (- 60F to 350F) and Celsius (- 51C to 177C).

(23)

FWD PRESS SW. A pressure switch in the transmission detects if the transmission has attained a

forward range. The readout is ON when there is forward pressure and OFF when there is no forward

pressure. Because the ATEC ECU needs input from both forward and reverse switches to determine

neutral range, refer to Step (24) (REV PRESS SW). Neutral is indicated when both readings are OFF.

(24)

REV PRESS SW. A pressure switch in the transmission detects if the transmission has attained a reverse

range. The readout is ON when there is reverse pressure and OFF when there is no reverse pressure.

Because the ATEC ECU needs input from both forward and reverse switches to determine neutral range,

refer to Step (23) (FWD PRESS SW). Neutral is indicated when both readings are OFF.

(25)

When the transmission has been placed in reverse range, the readout indicates ON as a reverse warning

signal. When the transmission is shifted from reverse range, the readout displays OFF.

NOTE

Oil level and fluidic sensor systems are used to detect low oil level conditions. The

readout is OFF when a low oil level condition is detected. The readout is ON when the

oil level is above the low oil level detection point.

(26)

Oil lube/LVL SW. This type of oil condition indicator is fluidic. The switch is used in the PLS truck.

(27)

Retard request. On the PLS truck, an instrument panel-mounted control is used to request operation of

the engine brake. The readout indicates ON when the engine brake is requested and OFF when the

engine brake is not requested. Refer to Step (28) (Retard command) for further information.

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