D6N Track-Type Tractor Electronic Control (Power Train System) Caterpillar


Electronic Control (Power Train System)
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1.1. Electronic Control Modules
2.2. Machine ECM
3.2. ECM Pull Up Voltage
4.2. ECM Pull Down Voltage
5.1. Pin Locations
6.1. Inputs
7.2. Sensors
8.3. Transmission Output Speed Sensors
9.3. Torque Converter Output Speed Sensor
10.3. Torque Converter Oil Temperature Sensor
11.3. Transmission Sump Temperature Sensor
12.3. Deceleration Pedal Sensor
13.3. Service Brake Pedal Position Sensor
14.3. Forward Neutral Reverse Sensor
15.3. Engine Speed and Bi-Direction Control
16.2. Switches
17.3. Forward and Reverse Switches
18.3. Parking Brake
19.3. Transmission Filter Bypass Switch
20.3. Upshift and Downshift Switches
21.1. Outputs
22.2. Proportional Solenoids
23.3. Transmission Clutch Solenoids
24.3. Brake Solenoid
25.2. On/Off Solenoids
26.3. Brake Dump Solenoid
27.1. Data Link
28.2. Cat Data Link
29.2. CAN Data Link

Electronic Control Modules

Machine ECM



Illustration 1g03307257


Illustration 2g01309473
ECM Connectors and Contacts

The Machine ECM determines actions that are based on input information and memory information. After the Machine ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the Machine ECM are connected to the machine harness by two 70 contact connectors (J1 and J2). The ECM sends the information to the AVSpare Electronic Technician (Cat ET) on the Cat Data Link.

Note: The ECM is not serviceable. The ECM must be replaced if the ECM is damaged. Replace the ECM if a failure is diagnosed.

ECM Pull Up Voltage

In order to aid in diagnostics of certain types of electrical circuits that are controlled by the ECM, an internal "pull up voltage" is connected to ECM switch and sensor signal input contacts. An above normal voltage is internally connected to the ECM signal input circuit through a resister.

During normal operation, the switch or sensor signal will hold the circuit low or at a certain signal amplitude, however, circuit conditions such as a loss of power to the component, a disconnection, or an open circuit will allow the circuit to be pulled high by the ECM pull up voltage. This condition will result in an above normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 03 (voltage above normal) diagnostic code for the affected circuit.

The types of ECM input circuits that have pull up voltage present are:

  • Pulse Width Modulated (PWM) sensor input circuits

  • Switch to Ground Input switch input circuits

  • Active analog (voltage) input signal circuits

  • Passive analog (resistance) input signal circuits

ECM Pull Down Voltage

In order to aid in diagnostics of electrical circuits that are controlled by the ECM, an internal "pull down voltage" is connected to ECM switch to battery type input circuits.

During normal operation, the switch contacts that are allowing the connection to a voltage source will hold the circuit high. When circuit conditions such as a loss of power to the switch supply voltage, a disconnection in the switch circuit or an open circuit will allow the circuit to be pulled low by the ECM pull down voltage. This condition will result in a below normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 04 (voltage below normal) diagnostic code for the affected circuit.

Pin Locations

Table 1
Machine ECM Contact Description J1 Contact Descriptions(1) 
No.(2)  Type  Function 
Differential Speed Input +  Transmission Output Speed Sensor 1 + 
Differential Speed Input -  Transmission Output Speed Sensor 1 - 
Differential Speed Input +  Transmission Output Speed Sensor 2 + 
Differential Speed Input -  Transmission Output Speed Sensor 2 - 
10  Cat Data Link +  Cat Data Link + 
13  Battery Return  Battery - 
15  Differential Speed Input +  Torque Converter Output Speed Sensor + 
16  Differential Speed Input -  Torque Converter Output Speed Sensor - 
20  Cat Data Link -  Cat Data Link - 
22  Analog Input  Torque Converter Oil Temperature Sensor 
23  Battery Return  Battery - 
29  Analog Input  Transmission Oil Temperature Sensor 
31  Battery Power Input  Battery + 
33  Switch to Ground Input  Reverse Switch (N/O) 
34  Switch to Ground Input  Reverse Switch (N/C) 
35  Switch to Ground Input  Parking Brake Switch Engaged 
38  Battery Power Input  Battery + 
39  Battery Power Input  Battery + 
40  Switch to Ground Input  Parking Brake Switch Released 
44  Sensor Power Output  8V Supply 
45  Sensor Power Return  8V Return 
47  Battery Power Input  Battery + 
48  Sourcing Driver Output  Transmission Speed Clutch 1 
49  Sourcing Driver Output  Transmission Speed Clutch 2 
50  Sourcing Driver Return  PWM Return 1-4 
51  Sourcing Driver Output  Transmission Speed Clutch 3 
52  Sourcing Driver Output  Brake Proportional Solenoid 
56  Sensor Power Return  10V Return 
57  Battery Return  Battery - 
64  Switch to Ground Input  Power Train Filter Bypass Switch 
65  Switch to Ground Input  Transmission Reverse Clutch 
66  Sourcing Driver Output  Transmission Forward Clutch 
69  Sensor Power Output  10V Supply 
70  Battery Return  Battery - 
(1) Contacts that are not listed are not used.
(2) The connector contacts that are not listed are not used.

Table 2
Machine ECM Contact Description J2(1) 
No.(2)  Type  Function 
Sourcing Driver Output  Parking Brake Dump Valve Solenoid 
Sourcing Driver Return  Park Brake Return 
15  PWM Input  Decel Pedal Signal 
22  Return  Sensor / Driver Return 
28  Switch to Ground Input  Upshift Switch (N/O) 
29  Switch to Ground Input  Upshift Switch (N/C) 
30  Switch to Ground Input  Downshift Switch (N/O) 
31  Switch to Ground Input  Downshift Switch (N/C) 
32  PWM Input  Service Brake Position Sensor 
33  PWM Input  Direction Lever Position Sensor (FNR) 
36  Switch to Ground Input  Forward Switch (N/O) 
37  Switch to Ground Input  Forward Switch (N/C) 
50  PWM Input  Engine Throttle Switch 
51  PWM Input  Bi-Directional Switch 
67  CAN Data Link +  CAN A Data Link + 
68  CAN Data Link -  CAN A Data Link - 
(1) The ECM responds to an active input only when all of the necessary conditions are satisfied.
(2) The connector contacts that are not listed are not used.

Inputs

The machine has several different types of input devices. The ECM receives machine status information from the input devices and determines the correct output action that is needed in order to control machine operations based on memory and software parameters. The machine utilizes the following types of inputs: switch type and sensor type.

Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open signal, a grounded signal and + battery signal.

Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to the ECM can be one of several different types of electrical signals such as: pulse width modulated (PWM) signals, voltage signals and frequency input signals. Each possible input to the ECM is listed in the tables for the 70-pin connectors.

Inputs provide information to the ECM in the form of sensors or switches.

Sensors

Sensors provide information to the ECM about the intent of the operator or changing conditions. The sensor signal changes proportionally to the changing of operator input or changing conditions. The following types of sensor signals are used by the ECM.

Frequency - The sensor produces a signal and the frequency (Hz) varies as the condition changes.

Pulse width modulated - The sensor produces a signal. The duty cycle of the signal varies as the condition changes. The frequency of this signal is constant.

Analog - The ECM measures the voltage that is associated to a specific condition of the control.

Transmission Output Speed Sensors



Illustration 3g03706206

The ECM receives signals from the transmission output speed sensor as a frequency signal. The transmission output speed sensor is an active sensor. The signal indicates the rotational speed of the connection from the output of the torque converter to the input of the transmission. The signal is generated by a gear passing in front of the sensor, with one full pulse generated per tooth on the gear. The signal is low when a gear tooth is in front of the sensor and high when in a valley.

Torque Converter Output Speed Sensor



Illustration 4g03706206

The ECM receives signals from the torque converter output speed sensor as a frequency signal. The torque converter output speed sensor is a passive sensor. The signal indicates the rotational speed of the connection from the output of the torque converter to the input of the transmission. The signal is generated by a gear passing in front of the sensor, with one full pulse generated per tooth on the gear. The sensor has an inductive coil that creates a voltage pulse to the ECM when a gear tooth passes the sensor. The ECM interprets the frequency of the pulses as the speed of the gear.

Torque Converter Oil Temperature Sensor



Illustration 5g03372390

The ECM receives signals from the torque converter oil temperature sensor as an analog signal. The sensor is a passive sensor. The voltage output of the sensor changes proportionally to the temperature of the torque converter oil.

Transmission Sump Temperature Sensor



Illustration 6g03372390

The ECM receives signals from the transmission sump oil temperature sensor as an analog signal. The sensor is a passive sensor. The voltage output of the sensor changes proportionally to the temperature of the transmission oil.

Deceleration Pedal Sensor



Illustration 7g03673784

The deceleration pedal position sensor is an active pulse width position sensor. The sensor sends a pulse width modulated signal to the ECM. The signal allows the ECM to determine the position of the service brake pedal.

Service Brake Pedal Position Sensor



Illustration 8g03373852

The service brake pedal position sensor is an active pulse width position sensor. The sensor sends a pulse width modulated signal to the ECM. The signal allows the ECM to determine the position of the service brake pedal.

Forward Neutral Reverse Sensor



Illustration 9g03674106

The forward neutral reverse sensor is an active pulse width position sensor. The sensor sends a pulse width modulated signal to the ECM. The signal allows the ECM to determine the operator request for direction of movement.

Engine Speed and Bi-Direction Control



Illustration 10g03674139

The engine speed and bi-direction control knobs act as multiple position switches. The two knobs generate specific PWM signals depending on the position of each knob. The ECM uses the two PWM signals to determine the operator request for engine speed and bi-direction. The following table shows the PWM signal associated with each position.

Table 3
Engine Speed and Bi-Direction Control Sensor 
Engine Speed Control  Bi-Direction Control 
Position  Duty Cycle  Position  Duty Cycle 
Speed 1 (Lowest)  10%     
Speed 2  23%  Off  23% 
Speed 3  36%  1st Gear Forward 1st Gear Reverse  36% 
Speed 4  49%  1st Gear Forward 2nd Gear Reverse  49% 
Speed 5  62%  2nd Gear Forward 1st Gear Reverse  62% 
Auto Shift (auto-kickdown, MVP, FER))  75%  2nd Gear Forward 2nd Gear Reverse  75% 
Speed 6 (Highest)  88%     

Switches

Switches provide an open signal, a ground signal, or a +battery signal to the inputs of the ECM. Switches are open or closed.

  • When a switch is open, no signal is provided to the corresponding input of the ECM. This “no signal” condition is also called “floating”.

  • When a switch is closed, a ground signal or a +battery signal is provided to the corresponding input of the ECM.

Forward and Reverse Switches



Illustration 11g03587184

The forward and reverse switches are single pole limit switches. The forward and reverse switches each have a normally open contact and a normally closed contact. When the switch is not activated, the normally open contact floats to a high voltage state, and the normally closed contact is pulled to a low voltage state. When the switch is activated, the normally open contact is pulled to a low voltage state, and the normally closed contact floats to a high voltage state. The ECM monitors the state of the two contacts for each switch and determines the operator request for forward or reverse movement.

Parking Brake



Illustration 12g03673551

The parking brake switch is a two position switch with a normally open contact and a normally closed contact. The contacts provide switch to ground inputs to the ECM. Through these contacts, the ECM can determine if the parking brake is engaged or disengaged. When the parking brake is activated, the switch prevents the ECM from energizing the brake solenoid, preventing the brakes from being released.

Transmission Filter Bypass Switch



Illustration 13g03320660

The transmission filter bypass switch is a pressure switch. The switch alerts the ECM when the oil filter is being bypassed. The contact floats to a high voltage when the switch is not closed. When the switch closes, the contact is pulled to a low or ground voltage state by the return line.

Upshift and Downshift Switches



Illustration 14g03588881

The upshift and downshift switches are single pole push-button switches. Each switch has a normally connected contact and a normally open contact. The ECM monitors the two contacts and determines the operator request to either upshift or downshift.

Outputs

The ECM responds to decisions by sending electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the operator or the service technician.

Proportional Solenoids

Transmission Clutch Solenoids



Illustration 15g03587899
Forward clutch solenoid
Reverse clutch solenoid
First gear clutch solenoid
Second gear clutch solenoid
Third gear clutch solenoid

Each of these solenoid valves is designed to control the flow of to a clutch plate. When the solenoid is not engaged or receiving a low duty cycle signal, the solenoid does not allow Power Train hydraulic oil to engage a clutch plate. As the duty cycle of the signal to the solenoid increases, the solenoid allows some flow and the clutch begins to engage. When the duty cycle of the signal to the solenoid is at the maximum, the flow of Power Train hydraulic oil fully engages the clutch. The engagement of a clutch is proportional to the duty cycle of the signal sent by the ECM.

Note: The solenoid coils are not designed to operate using 24 DCV directly. The ECM sends a PWM signal of 24 V at a duty cycle that will provide the necessary current to the solenoid coils. Do NOT activate the coils by using 24 DCV (+battery). The life of the coils will be reduced drastically. A source of 12 DCV should be used, if the coils must be activated by not using the ECM.

Brake Solenoid



Illustration 16g03372925

The brake solenoid is designed to control the flow of brake oil to the brakes. The brakes are spring applied and hydraulically released. When the solenoid is not engaged or receiving a low duty cycle signal, the solenoid does not allow brake oil to disengage the brakes. As the duty cycle of the signal to the solenoid increases, the solenoid allows some flow and the brakes begin to release. When the duty cycle of the signal to the solenoid is at the maximum, the flow of brake oil fully releases the brakes. The engagement of the brakes is inversely proportional to the duty cycle of the signal sent by the ECM.

Note: The solenoid coils are not designed to operate using 24 DCV directly. The ECM sends a PWM signal of 24 V at a duty cycle that will provide the necessary current to the solenoid coils. Do NOT activate the coils by using 24 DCV (+battery). The life of the coils will be reduced drastically. A source of 12 DCV should be used, if the coils must be activated by not using the ECM.

On/Off Solenoids

Brake Dump Solenoid



Illustration 17g03373579

The brake dump solenoid is an on/off solenoid valve. The solenoid is activated when the limit switch on the brake pedal is activated. The solenoid controls if the brake hydraulic oil is being directed to the tank, or allowed to be distributed by the brake solenoid.

Data Link

Electronic communication between the Machine Control ECM, the Engine ECM, and the other control modules on the machine is conducted over data link circuits. The data link circuits allow the sharing of information with other electronic control modules. The data link circuits are bidirectional. The data link circuit allows the ECM to send information and to receive information.

The electronic communication system consists of two types of data link systems.

  • Cat Data Link

  • SAE J1939 (CAN) Data Link

The two types of data links are the main structure for communication between all of the control modules on the machine.

The SAE J1939 Data Link circuit is mostly used for faster operational communication between the control modules on the machine. The Cat Data Link is used for some of the internal communication that does not require the faster speeds and is used for communication with external devices such as the AVSpare Electronic Technician (Cat ET) service tool.

Cat Data Link

The Cat Data Link is an input/output of the ECM. The data link uses the connector for the service port in order to communicate with the AVSpare Electronic Technician. A data link connection is provided for the product link.

Note: The control for the product link provides a global positioning system for the machine.

The data link is bidirectional. The bidirectional link allows the ECM to input information and output information. The data link consists of the following parts: internal ECM circuits, the related harness wiring, the service tool connector and the connector for the product link. The Cat Data Link connects to the ECM at contact J1-10 (wire 893-GN(Green)) and contact J1-20 (wire 892-BR(Brown)).

  • The ECM receives commands from the Cat ET in order to change the operating modes. The Cat ET will read the service codes that are stored in the memory of the ECM. The Cat ET will clear the service codes that are stored in the memory of the ECM.

  • The ECM sends the input and the output information to the AVSpare ET.

Note: An electronic control module that uses the Cat Data Link will have a module identifier. The MID for the Machine Electronic Control Module is 039.

CAN Data Link

A data link is required for communication with the service tool (Cat ET) and the electronic control modules as well as instrument clusters and other devices that use this communications protocol. The data link is not used in order to broadcast any diagnostic information.

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