994K Wheel Loader Machine Systems Caterpillar

Electronic Control (Steering System)

Usage:

994K MM9

Electronic Control Module (ECM)

ECM

Show/hide table




Illustration 1	g03094428
(1) Connector view from ECM side (2) Connector view from harness side

The ECM decides based on input information and memory information. After the ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the ECM are connected to the machine harness by two 70 contact connectors (J1 and J2). The inputs and outputs to the ECM can be viewed through the Caterpillar Electronic Technician (Cat ET).

Note: Only the complete ECM is serviced (no lower levels components). The ECM must be replaced if the ECM is damaged. Replace the ECM if a failure is diagnosed.

Pin Locations

Show/hide table

Table 1
Implement ECM Connector J1 Contact Descriptions⁽¹⁾
No.	Type	Function
1	Key Switch Input	Key Switch On
12	Sourcing Driver Output	Pilot On/Off Solenoid
21	Sensor Power Return	5V Sensor Return
22	Analog Input	Hydraulic Oil Temperature Sensor
32	Switch to Ground Input	ECM Location Code Enable
33	Switch to Ground Input	Implement Lockout Switch (N/O)
34	Switch to Ground Input	Implement Lockout Switch (N/C)
35	Switch to Ground Input	Implement Pilot Filter Bypass Switch
40	Switch to Ground Input	Implement Tank Left-Hand Case Drain Bypass Switch
44	Sensor Power Output	8V Supply
45	Sensor Power Return	8V Return

Show/hide table

⁽¹⁾	System-specific pin locations

Show/hide table

Table 2
Implement ECM Connector J2 Contact Descriptions⁽¹⁾
No.	Type	Function
4	Sourcing Driver Return	ON/OFF Return
28	Switch to Ground Input	Steering Cooling Oil Filter Bypass switch
31	Switch to Ground Input	Oil Renewal System Full Level Switch
34	PWM Input	Backup Steering Pilot Oil Pressure Sensor
36	Switch to Ground Input	Steering Tank Oil Low-Level Switch
37	Switch to Ground Input	Implement Tank Low-Level Switch (Sensor)
41	PWM Input	Implement and Steering Pilot Pressure
42	PWM Input	Steering Oil Temperature Sensor
43	PWM Input	Steering Pilot Oil Pressure Sensor
47	Switch to Ground Input	Hydraulic Tank Return Filter Bypass Switch
52	Switch to Ground Input	Steering Tank Oil Full Level Switch
53	Switch to Ground Input	Implement Tank Oil Level Full Switch (Sensor)

Show/hide table

⁽¹⁾	System-specific pin locations

Show/hide table

Table 3
Transmission ECM Connector J1 Contact Descriptions⁽¹⁾
No.	Type	Function
1	Key Switch Input	Key Switch On
31	Sourcing Driver Output	Unswitched Battery
32	Switch to Ground Input	ECM Location Code Enable
33	Switch to Ground Input	Steering/Transmission Lock (NC)
34	Switch to Ground Input	Steering/Transmission Lock (NO)

Show/hide table

⁽¹⁾	System-specific pin locations

Inputs

The inputs describe the status of the machine systems. Two types of inputs exist. The inputs can be either a switch type or a sensor type. Switches provide an open, a ground, or a + battery signal to the inputs of the controller. Sensors (frequency, PWM, or voltage) provide a changing signal to the sensor inputs of the controller. The inputs to ECMs are listed in table .

Temperature Sensors

Hydraulic Oil Temperature Sensor

Show/hide table




Illustration 2	g02108634
Hydraulic Oil Temperature Sensor

The temperature sensor for the hydraulic oil informs the ECM of the temperature of the hydraulic system oil.

The sensor sends an analog signal to the Implement ECM indicating hydraulic oil temperature. The resistance range for this sensor is 33,650 ohms at −40° C (−40° F)to 18.6 ohms at 150° C (302° F).

Pressure Sensors

Show/hide table




Illustration 3	g03892500

Implement Pilot Supply Pressure Sensor

The pressure sensor sends a signal to the Implement ECM indicating system pressure. The pressure sensor outputs a pulse width modulated signal. The duty cycle of the signal will vary in proportion to the system pressure. These PWM signals are inputs to the ECM.

Steering Pump Pressure Sensor

The pressure sensor informs the ECM of system pressure. The pressure sensor output is a pulse width modulated signal. The duty cycle of the signals will vary in proportion to the system pressure. These PWM signals are inputs to the ECM. The ECM provides 8 V to the sensor.

Primary Steering Pressure Sensor

Switches

Switches provide one of the following types of inputs to the ECM:

Open
Ground
+Battery

Switches are devices that have two states, opened or closed.

When a switch is open, no signal is provided to the corresponding input of the ECM. This condition is also referred to as floating.
When a switch is closed, a ground signal or a +battery signal is provided to the ECM.

Steering and Transmission Lock

Show/hide table




Illustration 4	g03892626

The switch tells the ECM when the operator has the lock lever in the locked position.

Show/hide table

Table 4
Switch Status
Switch Position	Normally Open	Normally Closed
Locked	Closed	Open
Unlocked	Open	Closed

Implement Lockout Switch

Show/hide table




Illustration 5	g03094425

The Implement ECM will control the operation of the Implement Pilot Supply Solenoid according to the position of the Hydraulic Lockout Switch. Certain fault conditions will also cause the Implement ECM to use the solenoid valve to disable hydraulic operation.

The ECM will disable the operation of the Implement System when the switch is in the LOCK position.

When the switch is in the UNLOCK position, the normally closed switch contacts will ground the input circuit at ECM contact J1-34. When the ECM detects this grounded circuit, the ECM will energize the Implement Pilot Supply Solenoid. The energized solenoid will allow pilot oil to be supplied to the implement control valve.

When the switch is in the LOCK position, the normally open switch contacts will ground the input circuit at ECM contact J1-33. When the ECM detects this grounded circuit, the ECM will de-energize the ON/OFF output for the Implement Pilot Supply Solenoid. Pilot oil will be blocked from the implement control valve.

Implement Pilot Oil Filter Bypass Switch

Show/hide table




Illustration 6	g03094426

The bypass switch is a pressure switch that shows whether the filter is plugged and the filter is being bypassed. This switch is normally open. When electrical power is applied to the switch, the switch closes. When the filter becomes plugged, the pressure of the oil opens the switch which allows the oil to bypass the filter.

This switch is one of the inputs that is used to drive the "system indicator" in the instrument cluster. This indicator is turned ON when the "Implement pilot oil filter bypass" switch is in the closed position and the pilot oil temperature is greater than 52° C (126° F) with the engine running.

Implement Tank Right/Left Hand Case Drain Bypass Switch

This switch is one of the inputs that is used to drive the "system indicator" in the instrument cluster. This indicator is turned ON when the "Implement pump filter bypass" switch is in the closed position and the pilot oil temperature is greater than 52° C (126° F) with the engine running.

Hydraulic Tank Return Filter Bypass Switch

This switch is one of the inputs that is used to drive the "system indicator" in the instrument cluster. This indicator is turned ON when the "Hydraulic Tank Return Filter Bypass" switch is in the closed position and the pilot oil temperature is greater than 121° ± 3°C (250° ± 5°F) with the engine running.

Implement Tank Oil Level Full and Low Switch (Sensor)

Show/hide table




Illustration 7	g03094427

The implement tank oil level full and low sensor are switch to ground inputs to the implement ECM. These two components are sensors that function as switches. The implement tank oil level full/low sensors are used to monitor the implement tank oil level.

Outputs

The ECMs respond 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. The outputs of the ECM are listed in tables .

Solenoids

Show/hide table




Illustration 8	g03094422

Pilot On/Off Solenoid

This solenoid controls the Pilot On/Off Solenoid Valve, which enables or disables the pilot hydraulic system. When the Pilot On/Off Solenoid is energized, pilot oil flows to the Pilot Hydraulic Actuators. When de-energized, pilot oil is blocked at the solenoid valve.

Data Link

Cat Data Link

The Cat Data Link is an input/output of the ECM. The data link uses the connector for the service port to communicate with the Caterpillar 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 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 Caterpillar 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. The data link also communicates with the instrument clusters and other devices using this communications protocol. The data link is not used to broadcast any diagnostic information.