The Transmission ECU will have the ECU positive voltage lines of the battery run to unswitched battery in the vehicle harness. The key switch ON (C16: 7 to J1-1) pin on the Transmission ECU is run, to the key switch ON position in the vehicle and when it turns off, the software controls when the Transmission ECU actually shuts down.
When the key switch ON input turns OFF, the transmission software will continue to run normally until one of the following two conditions are met :
- The transmission output speed is zero and the transmission is the NEUTRAL position.
- The transmission output speed is zero and the engine speed is zero.
The second statement covers the event of the shift selector being left in gear or is faulted because it shuts down due to power being turned off. When the shift selector is faulted, the shift control logic holds the previous position of the shift selector and will not shift to NEUTRAL as long as the shift selector is faulted and was previously in a gear.
Transmission Filter Bypass Function
The transmission filter bypass function is used in order to warn the operator when the transmission filter is being bypassed. The filter could be plugged due to contamination. The red warning lamp indicator is turned ON in order to warn the operator.
The filter bypass input is a switch to common. If this input has a closed circuit, then the filter is not bypassing (OK). If the input has an open circuit, then the filter is bypassing (PLUGGED). A warning will occur if the input wire to the ECU breaks. If the oil is not bypassing and an open circuit exists, then the harness needs checked and repaired. When the transmission filter bypass input indicates that the filter is plugged, an event is logged and the transmission warning lamp is activated.
When the engine speed increases to a predetermined level, the Transmission ECU will upshift. The transmission will shift ONE gear position past the operator's selection in order to protect the engine from overspeed.
Customer password protected programmable parameter with a programmable range of 0-65535 N·m. This configurable parameter is used to limit engine torque to protect driveline components. This value reflects significant margin on the most aggressive torque converter match for on-highway applications. The customer parameter is programmable with Cat ET.
Note: DO NOT CHANGE FACTORY SETTINGS.
Directional Shift Management Function
The Transmission ECU will not allow a directional change if the engine speed is above 1000 rpm or transmission output speed is above 150 rpm. If either of these conditions are not met when the operator commands a directional shift, then the transmission will shift to NEUTRAL and the desired gear display will flash. The operator will then have to select NEUTRAL before selecting FORWARD or REVERSE after this has occurred.
The check transmission lamp function turns on when there is a diagnostic that is active. This lamp is an amber colored lamp.
Note: The check transmission lamp driver output will turn on for 5 seconds at power up, then turn off for 0.5 seconds before going to normal mode. This mode is for a bulb check on power up of the system.
The warning lamp turns on when there is a transmission over temp event or transmission filter bypass event. This event is for the red transmission warning lamp in the dash. The lamp turns on at a specific torque converter temperature and turns off at a lower temperature. The temperature set points for this feature can be programmed to the following values:
- Torque Converter High Temperature Turn On : 151 °C (304 °F)
- Torque Converter High Temperature Turn Off : 142 °C (287 °F)
- Transmission Sump High Temperature Turn On : 121 °C (250 °F)
- Transmission Sump High Temperature Turn Off : 113 °C (235 °F)
The speed enable output is an output driver that turns ON when the engine exceeds the programmed engine speed or output speed value. The output turns off when the engine speed goes below a programmed speed value. This output can be used to turn on a lamp when a specific output speed is being exceeded or to enable some vehicle functionality when a specific engine speed or output speed is reached. This output requires some programming to enable it and to set the turn on and off speeds.
The programmable parameters would be as follows:
- Speed Enable Output: OFF/Engine Speed/Output Speed/PTO Engine Speed
- Speed Enable Turn On RPM: 0-5000 rpm default: 5000
- Speed Enable Turn Off RPM: 0-5000 rpm default: 5000
The speed enable output will not change state if the programmable parameter is programmed to OFF. If the speed enable output is programmed to "Engine Speed", then the output turns on when engine speed exceeds the "Speed Enable turn On RPM" programmed value. It will turn off when the engine speed is below the programmed "Speed Enable turn Off RPM" value. If the "Speed Enable Output" parameter is programmed to "Output Speed", then output speed is used to turn on and off the speed enable output. If the "Speed Enable Output" is programmed to "PTO Engine Speed", then the output is turned on when engine speed exceeds the "Turn On RPM" and the "Transmission PTO" mode is active. If the "Transmission PTO" mode is not active, then the "Speed Enable Output" will not turn on under this programmed mode.
High Transmission Oil Temperature
There are warnings when the torque converter oil temperature reaches a set value. The on-highway engine electronic control usually controls the fan on the truck, but it is not looking at the transmission oil temperature. But, via the J1939 data link, the transmission can send a message to turn on the engine fan. The Transmission ECU will request the fan to turn on when the torque converter oil temperature or transmission sump oil temperature goes above the turn on value and then turn off when both torque converter temperature and transmission sump oil temperature go below the turn off temperature.
- Fan Turn On Oil Temp: 129 °C (264 °F)
- Fan Turn Off Oil Temp: 121 °C (250 °F)
During downhill operations the transmission may request the engine to engage the cooling fan to provide additional braking force for the vehicle. This request will happen over the J1939 data link. The transmission has no operator controlled inputs for the engine cooling fan control.
Conditions for the cooling fan to be engaged for additional vehicle braking:
- Transfer case is in low range and maximum selected gear is 4 or less than 4
- Transfer case is in high range and maximum selected gear is 2 or less than 2
- Engine speed less than 2800 RPM (the cooling fan may not be engaged at high engine RPM)
- Engine exhaust brake is active