Transmission (AT/MT/HT) Relay Circuit

405

TM 9-2320-312-24-2

Troubleshooting Section

Note: JUL99 and newer Personality Modules have

i01611424

a programmable "AT/MT/HT Part Throttle Shift

Transmission (AT/MT/HT)

Speed" parameter that provides three different

Relay Circuit - Test

shift modulation settings for the transmission. The

"Low" setting will disable the relay below 65 percent

throttle, the "Medium" setting below 55 percent

SMCS Code: 1901-081

throttle, and the "High" setting below 45 percent

throttle.

System Operation Description:

The AT/MT/HT transmission interface relay will be

Use this procedure under the following situation:

enabled under any the following conditions:

Use this procedure to determine if the AT/MT/HT

The engine is running.

transmission interface relay (output #7) is operating

correctly.

The transmission is in gear or the speed of the

vehicle is greater than 24 km/h (15 mph) (NOV99

The following background information is related

and older Personality Modules).

to this procedure:

The accelerator pedal position is greater than 80

Allison AT/MT/HT transmissions require an input

percent of the programmed value. Refer to the

from the ECM to regulate the transmission shifting.

note below.

The ECM monitors various operating parameters

in order to determine if the transmission should

Note: JUL99 and newer Personality Modules have

use closed throttle shift modulation or full throttle

a programmable "AT/MT/HT Part Throttle Shift

shift modulation. Programming the "Transmission

Speed" parameter that provides three different

Style" parameter to "AT/MT/HT Option1", "AT/MT/HT

shift modulation settings for the transmission. The

Option2", "AT/MT/HT Option3", or "AT/MT/HT

"Low" setting will enable the relay above 80 percent

Option4" activates ECM Output #7 in order to

throttle, the "Medium" setting above 70 percent

control a shift interface relay that is connected to

throttle, and the "High" setting above 60 percent

the Allison transmission.

throttle.

Transmission Style

Cruise Control or Vehicle Speed Limiting is

active.

For engines that have a Full Feature ECM, the

"Transmission Style" must be programmed to one

The AT/MT/HT transmission interface relay will be

of the AT/MT/HT options in order for Output #7 to

disabled when all of the following conditions occur:

control the AT/MT/HT transmission relay. For the

"Basic (GM) System", Output #7 is always available.

The speed of the vehicle is greater than 2 km/h

(1 mph) of the cruise set speed or the vehicle

Note: The ECM does not communicate with the

speed limit.

Allison AT/MT/HT Transmission through a data link.

The load factor is less than 75 percent.

Cruise Control or Vehicle Speed Limiting is NOT

active.

The engine speed is greater than 2000 rpm.

The AT/MT/HT transmission interface relay will be

The transmission interface relay will be enabled

disabled if any of the following conditions occur:

when the load factor is greater than 98 percent.

The engine is not running.

The transmission is in neutral and the speed of

the vehicle is less than 24 km/h (15 mph) (NOV99

and older Personality Modules).

The accelerator pedal position is less than 65

percent of the programmed value. Refer to the

note below.