966G Wheel Loader and 972G Wheel Loader Power Train Caterpillar

Switches provide three types of switch inputs to the power train electronic control module (ECM), an open signal, a ground signal or a +battery signal. Switches are open or closed.

• When the switch is open, no signal is provided to the corresponding input of the power train ECM.

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

Rocker Switch (Transmission Neutralizer Override Control) for Machines without Integrated Braking System

Illustration 1	g00287661
Transmission Neutralizer Override Switch

The transmission neutralizer override switch is an input of the power train electronic control module (ECM). The transmission neutralizer override switch signals the power train ECM to enable the neutralizer function.

The transmission neutralizer override switch is a two-position rocker switch. When the switch is activated, the switch closes connector contact J2-4 to ground. When the switch is deactivated, the switch is open. The switch has six terminals. Terminals 5 and 6 are used to turn on the neutralizer override indicator in the dash. Terminal A and terminal B turn on the internal switch indicator. Terminal 3 connects to connector contact J2-4 of the power train ECM. Terminal 2 connects to the ground.

Reference: For more information on the transmission neutralizer function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the transmission neutralizer switch, refer to the Service Manual module Operation and Maintenance Manual for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Momentary Switch (Transmission Neutralizer Override Control) for Machines with Integrated Braking System

Illustration 2	g00774219
Switch (Transmission Neutralizer Override Control) (1) Open Connection. (2) + Battery. (3) Closed Connection. (A) ground. (B) Neutralized Signal

The transmission neutralizer override switch is an input to the power train electronic control module (ECM). The transmission neutralizer override switch signals the power train ECM to enable the neutralizing function for the transmission.

The transmission neutralizer override switch is a momentary switch. When the transmission neutralizer override switch is activated, contact J1-34 will be connected to the +Battery connection. When the transmission neutralizer override switch is activated the transmission will stay neutralized until the switch is pushed again or until the engine is shut off. When the switch is released, the switch is open. Terminal A and terminal B turn on the internal switch indicator.

Reference: For more information on the transmission neutralizer function, refer to the Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to theSystems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Rotary Switch (Variable Shift Control)

Illustration 3	g00779624
Variable Shift Control Switch

The variable shift control switch is an input of the power train ECM. The switch allows the selection of a range of points to shift the transmission for each speed. The switch has three inputs to the power train ECM. The combination of inputs for each switch position are shown in the following table.

Reference: For more information on the variable shift control, refer to the Service Manual module Systems Operation, "Rotary Switch (Variable Shift Control)" for the machine that is being serviced.

Table 1

Variable Shift Control Switch Status Conventional Steering
Switch Position	Economy J1-20	Moderate J1-24	Aggressive Full Throttle J1-35
Economy	Closed	Open	Open
Moderate	Open	Closed	Open
Aggressive Full throttle	Open	Open	Closed

Table 2

Variable Shift Control Switch Status Command Control Steering
Switch Position	Economy J1-20	Moderate J1-24	Agressive Full Throttle J1-35
Economy	Closed	Open	Open
Moderate	Open	Closed	Open
Agressive Full throttle	Open	Open	Closed

Limit Switch (Transmission Neutralizer) for Machines without Integrated Braking System

Illustration 4	g00287699
Limit Switch (Transmission Neutralizer)

The transmission neutralizer limit switch is located in the cab in the left brake pedal assembly. The neutralizer switch is a two-position limit switch. The neutralizer switch informs the power train electronic control module (ECM) when the operator depresses the left brake pedal. When the left brake pedal is depressed, the transmission neutralizer limit switch is actuated. When the transmission neutralizer limit switch is actuated, the transmission neutralizer limit switch signals the power train ECM to shift the transmission to neutral. When the neutralizer switch is activated, the switch is open. When the neutralizer switch is deactivated, the switch closes connector contact J2-4 of the power train ECM to ground. When connector contact J2-4 is not grounded, the power train ECM initiates the transmission neutralizer function. The normally closed (N/C) terminal of the switch connects to the transmission neutralizer override switch. The COM terminal connects to ground.

Note: The transmission neutralizer limit switch is wired in parallel with the transmission neutralizer override switch. Both switches connect to the neutralizer input of the power train ECM. The neutralizer input of the power train ECM is located at connector contact J2-4.

Reference: For more information on the transmission neutralizer function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the transmission neutralizer switches, refer to the Operation and Maintenance Manual for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Pressure Switch (Parking Brake Oil)

Illustration 5	g00287701
Parking Brake Pressure Switch

The parking brake pressure switch is an input of the power train electronic control module (ECM). This switch informs the power train ECM when the parking brake is engaged.

The parking brake pressure switch is a double-pole, single-throw pressure switch. When the operator engages the parking brake, the normally open (N/O) pole opens and the normally closed (N/C) pole closes to ground. This tells the power train ECM that the parking brake is engaged. When the parking brake is disengaged, the N/O pole is closed and the N/C pole is open. This tells the power train ECM that the parking brake pressure switch circuit is operating correctly. No action is required. The N/C pole connects to connector contact J1-27 of the power train ECM. The N/O pole connects to connector contact J1-36 of the power train ECM. The common terminal of the switch connects to ground.

Note: The normally closed (N/C) circuit and normally open (N/O) circuit of the parking brake pressure switch are used for diagnostic purposes. A circuit failure is present if the two circuits are open at the same time or if the two circuits are grounded at the same time. This fault is then shown on the display of the power train ECM.

Reference: For more information on the diagnostic operations, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the parking brake function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Conventional Steering Shift Switches

Switch (Transmission Direction and Speed Control Lever)

Illustration 6	g00488780
Transmission Direction and Speed Control Lever of a Machine that is Equipped with Conventional Steering (1) Transmission direction and speed control lever.

Illustration 7	g00328467
Transmission Direction and Speed Control Lever

The switches in the transmission direction and speed control lever are inputs to the power train electronic control module (ECM). The switches send information to the power train ECM about the speed that has been selected and the direction that has been selected with the transmission direction and speed control lever. The switches close the direction/speed inputs to ground on the power train ECM.

Reference: For more information on the function of the transmission direction and speed control lever, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Switch (Transmission Downshift)

Illustration 8	g00493863
Downshift Switch

The downshift switch signals the power train electronic control module (ECM) to downshift the transmission by one speed. To downshift, the operator depresses the downshift switch. The downshift switch has two input connections to the power train ECM on connector J1: downshift N/C at contact 25 and downshift N/O at contact 26. When the operator presses the downshift switch, the downshift N/C circuit is open and the downshift N/O circuit is closed to ground. When the downshift switch is not activated, the downshift N/C circuit is closed to ground and the downshift N/O circuit is open or floating.

Reference: For more information on the function of the transmission downshift switch, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Rotary Switch (Transmission Auto/Manual) for Machines without Integrated Braking System

Illustration 9	g00328469
Transmission Auto/Manual Switch for a machine that is equipped with Conventional Steering

The two-position auto/manual switch tells the power train electronic control module (ECM) of the desired shift mode, AUTO mode or manual mode. The switch has two input connections to the power train ECM on connector J1: AUTO mode at contact 31 and manual mode at contact 29. Two switch contacts are used for diagnosing a failure of the switch. A circuit failure is present if both of the switch contacts are open at the same time or if the two switch contacts are grounded at the same time. The valid combinations for each switch position are shown in table 3 that follows.

Reference: For more information on the function of the autoshift control, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Rotary Switch (Transmission Auto/Manual) for Machines with Integrated Braking System

The Auto/Manual switch sends an input to the power train ECM. The switch is used to select the top speed of the transmission when the transmission is in auto mode. The auto/manual switch has three inputs. One position is for the manual mode. The other two positions are for auto mode. The following table gives the combinations of the switch positions.

Table 3

Auto/Manual Switch Status
Switch Position	Manual J1-29	Auto 1-4 J2-5	Auto 2-4 J1-31
Auto 1-4	Open	Closed	Open
Auto 2-4	Open	Open	Closed
Manual	Closed	Open	Open

Command Control Steering Shift Switches

Switch (Transmission Direction Control)

Illustration 10	g00488783
Transmission Direction and Speed Control of a Machine that is Equipped with Command Control Steering (2) Transmission direction control switch. (3) Transmission upshift switch. (4) Transmission downshift switch.

Transmission direction control switch (2) is located on the steering wheel. Transmission upshift switch (3) and transmission downshift switch (4) are located on the steering wheel. Transmission direction control switch (1) is a three-position switch that selects either forward, neutral, or reverse.

The operator selects a direction by moving transmission direction control switch (1) to one of three positions. Transmission direction control switch (1) tells the power train electronic control module (ECM) the direction of travel that is selected. The following connections to the power train ECM are on connector J1: contact 30 (forward), contact 13 (neutral) and contact 14 (reverse). The selected switch position is grounded. The switch positions that are not selected are open. The valid combinations for each switch position are shown in table 4 that follows.

Reference: For more information on the function of the transmission direction control switch, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Table 4

Status of the Transmission Direction Control Switch Command Control Steering
Switch Position	J1-30	J1-13	J1-14
Forward	Closed	Open	Open
Neutral	Open	Closed	Open
Reverse	Open	Open	Closed

Switch (Transmission Upshift)

Illustration 11	g00488783
Transmission Direction and Speed Control of a Machine that is Equipped with Command Control Steering (2) Transmission direction control switch. (3) Transmission upshift switch. (4) Transmission downshift switch.

Transmission upshift switch (3) makes momentary contact in order to select the next higher speed. The operator selects a speed by depressing transmission upshift switch (3) or by depressing transmission downshift switch (4).

Transmission upshift switch (3) has two input connections at the power train electronic control module (ECM). The two input connections at the power train ECM on connector J1 follow: upshift N/C at contact 19 and upshift N/O at contact 23. When the operator presses the upshift switch, the upshift N/C circuit is open and the upshift N/O circuit is closed to ground. When the switch is not activated, the upshift N/C circuit is closed to ground and the upshift N/O circuit is open. The valid combinations for each switch position are shown in table 5 that follows.

Reference: For more information on the function of the transmission upshift switch, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Table 5

Status of the Transmission Upshift Switch Command Control Steering
Switch Position	N/C J1-19	N/O J1-23
Depressed	Open	Closed
Released	Closed	Open

Note: The normally closed (N/C) circuit and normally open (N/O) circuit of the transmission upshift switch is used for diagnostic purposes. If the normally closed (N/C) circuit and the normally open (N/O) circuit are open at the same time, the power train ECM records a fault. If the normally closed (N/C) circuit and the normally open (N/O) circuit are grounded at the same time, the power train ECM records a fault.

Switch (Transmission Downshift)

Illustration 12	g00488783
Transmission Direction and Speed Control of a Machine that is Equipped with Command Control Steering (2) Transmission direction control switch. (3) Transmission upshift switch. (4) Transmission downshift switch.

Transmission downshift switch (4) makes momentary contact in order to select the next lower speed. The operator selects a speed by depressing transmission upshift switch (3) or by depressing transmission downshift switch (4).

Transmission downshift switch (4) has two input connections to the power train electronic control module (ECM) on connector J1: downshift N/C at contact 25 and downshift N/O at contact 26. When the operator presses the downshift switch, the downshift N/C circuit is open and the downshift N/O circuit is closed to ground. When the switch is not activated, the downshift N/C circuit is closed to ground and the downshift N/O circuit is open. The valid combinations for each switch position are shown in table 6 that follows.

Reference: For more information on the function of the transmission downshift switch, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Table 6

Status of the Transmission Downshift Switch Command Control Steering
Switch Position	N/C J1-25	N/O J1-26
Depressed	Open	Closed
Released	Closed	Open

Note: The normally closed (N/C) circuit and normally open (N/O) circuit of the transmission downshift switch is used for diagnostic purposes. If the normally closed (N/C) circuit and the normally open (N/O) circuit are open at the same time, the power train ECM records a fault. If the normally closed (N/C) circuit and the normally open (N/O) circuit are grounded at the same time, the power train ECM records a fault.

Reference: For more information on the diagnostic operations, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Rotary Switch (Transmission Auto/Manual) for Machines without Integrated Braking System

Illustration 13	g00288389
Transmission Auto/Manual Switch for a Machine that is Equipped with Command Control Steering

The four-position auto/manual switch tells the power train electronic control module (ECM) of the desired shift mode, AUTO mode or manual mode. The switch is also used to select the top speed for the transmission when the transmission is in the AUTO mode. The switch has four input connections to the power train ECM on connector J1: Manual mode at contact 29, AUTO mode with a top speed of fourth speed at contact 31, AUTO mode with a top speed of third speed at contact 33, AUTO mode with a top speed of second speed at contact 32 and Auto mode with top speed of fourth speed at contact 35. The valid combinations for each switch position are shown in table 7 that follows. If an invalid combination is detected by the power train ECM, a circuit failure is present.

Reference: For more information on the function of the autoshift control, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Table 7

Status of the Transmission Auto/Manual Switch Command Control Steering
Switch Position	J1-29	J1-31	J1-32	J1-33
AUTO Speed 2	Open	Open	Open	Closed
AUTO Speed 3	Open	Open	Closed	Open
AUTO Speed 4	Open	Closed	Open	Open
Manual	Closed	Open	Open	Open

Rotary Switch (Transmission Auto/Manual) for Machines with Integrated Braking System

Illustration 14	g00779622
Auto/Manual Switch (5 Position)

The Auto/Manual switch sends an input to the power train ECM. The switch is used to select the top speed of the transmission when the transmission is in auto mode. The auto/manual switch has five inputs. One position is for the manual mode. The other four positions are for auto mode. The following table gives the combinations of the switch positions.

Reference: For more information on the auto shift control, refer to the Systems Operation, "Auto Shift Control" for the machine that is being serviced.

Table 8

Auto/Manual Switch Status
Switch Position	Man J1-29	Auto 4-2 J1-31	Auto 3-2 J1-33	Auto 2-2 J1-32	Auto 1-4 J1-10
Auto 1-4	Open	Open	Open	Open	Closed
Auto 2-2	Open	Open	Open	Closed	Open
Auto 2-3	Open	Open	Closed	Open	Open
Auto 2-4	Open	Closed	Open	Open	Open
Manual	Closed	Open	Open	Open	Open

Rocker Switch (Ride Control)

Illustration 15	g00288392
Ride Control Switch

The ride control switch informs the power train electronic control module (ECM) of the ride control mode that is selected. There are three ride control modes: AUTO, ON and OFF.

The ride control switch has two input connections to the power train ECM at connector J1: input 1 at contact 21 and input 2 at contact 22. When the operator selects the AUTO position, input 1 is closed to ground and input 2 is open. When the ON position is selected, input 1 is open and input 2 is closed to ground. When the OFF position is selected, input 1 and input 2 are closed to ground. The valid combinations for each switch position are shown in table 9 that follows.

Reference: For more information on the ride control function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Table 9

Status of the Ride Control Switch
Mode	Switch Position	J1-21	J1-22
ON	Up	Open	Closed
OFF	Center	Closed	Closed
AUTO	Down	Closed	Open

Start Switch (Key)

Illustration 16	g00291705
Key Start Switch

The key start switch is an input of the power train electronic control module (ECM). The key start switch informs the power train ECM of an attempt to start the engine. The power train ECM then initiates the neutral start function.

During normal machine operation, the start terminal of the key start switch is open. When the key start switch is turned to the START position, the start terminal closes to the +battery and the +battery voltage is present at connector contact J1-40 of the power train ECM. When all starting conditions are satisfied, the power train ECM sends a +battery signal to the connector contact J1-8 for the start relay and engine cranking begins.

Note: After the key start switch is initially turned to the START position, the switch will not return to the START position from the ON position. The switch must be turned to the OFF position first. Then, the switch can be turned to the START position.

Reference: For more information on the neutral start function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.

Reference: For more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.