826G Landfill Compactor, 825G Soil Compactor, 824G Wheel Dozer and 980G Wheel Loader Power Train Electronic Control System Caterpillar

• open

• ground

• +battery

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

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

Neutralizer Override Switch

Illustration 1	g00287661
Neutralizer Override Switch

The neutralizer override switch is an input of the power train ECM. This switch is used in order to signal the power train ECM that the operator wants the neutralizer function. Refer to Systems Operation, "Normal Operation" for more information about the neutralizer override switch.

The override switch is a two-position rocker switch. When the switch is activated, the switch closes contact J2-4 to ground. When the switch is deactivated the switch is open. The switch has six terminals. Terminal 5 and terminal 6 provide power to the indicator light for the neutralizer override switch that is located in the dash. Terminal A and terminal B provide power to the indicator light that is located in the neutralizer override switch. Terminal 3 connects to contact J2-4 of the power train ECM. Terminal 2 connects to the frame ground.

Neutralizer Switch (If Equipped)

Illustration 2	g00287699
Neutralizer Switch

The neutralizer switch is a two-position limit switch. The neutralizer switch informs the power train ECM when the operator presses the left brake pedal. When the neutralizer switch is activated the switch is open. When the neutralizer switch is deactivated, the switch closes contact J2-4 of the power train ECM to ground. When contact 4 is NOT grounded, the power train ECM initiates the neutralizer function. Refer to Systems Operation, "Normal Operation" for additional information on the operation of neutralizer function. The N/C terminal of the switch connects to the neutralizer override switch. The COM terminal connects to frame ground.

Note: The neutralizer switch in the left pedal is wired in parallel with the neutralizer override switch. Both switches connect to J2-4. This is the input for the power train ECM.

Pressure Switch (Parking Brake Oil)

Illustration 3	g00287701
Parking Brake Pressure Switch

The parking brake pressure switch is an input of the power train ECM. This switch informs the power train ECM that the parking brake is engaged.

The parking brake pressure switch is a single-pole single throw. When the operator engages the parking brake, the N/O pole opens and the 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 informs the power train ECM that the parking brake switch circuit is operating correctly and no action is required. The N/C pole connects to contact J1-27 of the power train ECM. The N/O pole connects to contact J1-36 of the power train ECM. The common terminal of the switch connects to ground.

Note: Two circuits (N/C and N/O) for the parking brake limit switch are used for diagnostic purposes. If the two circuits are open at the same time or grounded at same time, the power train ECM detects a circuit failure. This diagnostic code is then shown on the display of the power train ECM. Refer to System Operation, "Diagnostic Operation" for additional information.

If the parking brake is engaged with the transmission in speed 1, the power train ECM shifts the transmission to neutral. The power train ECM also sends the parking brake status to Caterpillar Monitoring System over the CAT data link. When the parking brake is engaged, the alert indicator for the parking brake FLASHES on Caterpillar Monitoring System. If the operator selects FORWARD or REVERSE with the parking brake engaged, the Caterpillar Monitoring System initiates a category 3 warning. With a category 3 warning, the following warnings will result: FLASHING of the parking brake indicator, FLASHING of the action lamp and SOUNDING of the action alarm .

The power train ECM also has other features that are related to the parking brake status. For more information about parking brake operation, refer to System Operation, "Normal Operation".

Switches (Shift)

Upshift, Downshift, and Direction

Illustration 4	g00288377
Shift Switches in Steering Wheel (1) Upshift switch. (2) Downshift switch. (3) Direction switch.

The following switches are mounted in the steering wheel: Upshift switch (1), downshift switch (2) and direction switch (3). These switches are inputs to the power train ECM.

The upshift switch tells the power train ECM that the operator wants the transmission to upshift one gear. In order to upshift, the operator presses and the operator briefly holds the upshift switch. The upshift switch has two input connections at the power train ECM. The two input connections at the power train ECM are upshift N/C at connector J1 contact 19 and upshift N/O at connector J1 contact 23 of the power train ECM. 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 downshift switch tells the power train ECM that the operator wants the transmission to downshift one gear. In order to downshift, the operator presses and the operator briefly holds the downshift switch. The downshift switch has two input connections to the power train ECM. These connections are downshift N/Cat connector J1 contact 25 and downshift N/O at connector J1 contact 26 of the power train ECM. When the operator presses the downshift switch, the downshift N/C circuit is open or floating. The downshift N/O circuit will be 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.

Note: The status for the two inputs for the upshift and the status for the two inputs for the downshift must be correct. The power train ECM will use this information in order to make each shift.

Note: Two circuits (N/C and N/O) for the downshift switch and the upshift switch are used for diagnostic purposes. If the two circuits are ever in the same state, the power train ECM records a diagnostic code.

The direction switch has the following positions: forward (neutral) and reverse. The direction switch is used by the operator in order to change these positions. A signal is sent to the power train ECM. The connections for the power train ECM follow: forward at connector J1 contact 30, neutral at connector J1 contact 13 and reverse at connector J1 contact 14. The selected switch position is grounded. The switch positions that are not selected are open.

Auto/Manual Switch

Four Position

Illustration 5	g00288389
Auto/Manual Switch

The Auto/Manual switch tells the power train ECM that the operator wants the transmission to change modes. The switch is also used to select the top gear for the transmission when the Auto mode is selected. The switch has four input connections to the power train ECM: Auto/Manual/Top 1 contact at J1-29, Auto/Manual/Top 2 at contact J1-31, Auto/Manual/Top 3 at contact J1-32 and Auto/Manual/Top 4 at contact J1-33. The valid inputs for each switch position are shown in the table that follows. If an invalid input is detected by the power train ECM, the power train ECM records a diagnostic code.

Five Position

Illustration 6	g00772851
Auto/Manual Switch (Integrated Braking System)

The Auto/Manual switch for the integrated braking system tells the power train ECM that the operator wants the transmission to change modes. The switch is also used to select the top gear for the transmission when the Auto mode is selected. The switch has five input connections to the power train ECM. The valid input for each switch position is shown in the table that follows. If an invalid input is detected by the power train ECM, the power train ECM records a diagnostic code.

Switch (Variable Shift Control)

Illustration 7	g00772933
Variable Shift Control Switch

The variable shift control switch is an input of the power train ECM. The switch allows the operator to select a range of operation for the variable shift control feature. The switch has three inputs to the power train ECM. The valid inputs for each switch position are shown in the table that follows. If an invalid input is detected by the power train ECM, the power train ECM records a diagnostic code.

Switch (Ride Control)

Illustration 8	g00288392
Ride Control Switch

Note: The information for the ride control switch is only applicable for the 980G.

The ride control switch tells the power train ECM that the operator wants the transmission to change modes. Refer to System Operation, "Normal Operation" for more information about "Ride Control Operation".

The ride control switch has two input connections to the power train ECM. Input 1 at connector contact J1-21 and input 2 at connector contact J1-22 are the two input connections to the power train ECM. The valid input for each switch position is shown in the table that follows.

Key Start Switch

Illustration 9	g00291705
Key Start Switch

The key start switch is an input of the power train ECM. The key start switch tells the power train ECM that the operator wants to start the engine. The power train ECM then initiates the neutral start function. Refer to System Operation, "Normal Operation" for more information about the neutral start operation. During normal machine operation, the start terminal of the key start switch is open. When the key start switch is turned and the key start switch is held in the START position, the start terminal closes to the +battery. Then +battery voltage is present at connector J1-40 of the power train ECM. When all starting conditions are satisfied, the power train ECM sends a +battery signal to the start relay (connector J1-8) 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 first be turned to the OFF position., Then, the switch can be turned to the START position.

Options Code Plug

The options code plug is an input of the power train ECM. The options code plug is used to recognize the options that are installed on the machine. This tells the power train ECM the way to function.

The inputs of the options code plug are either open or the inputs are grounded. The input connectors are J1contacts 39, 24, 20 and 35. The ECM interprets the status of the contacts and functions accordingly. The following table lists the options that are available. The options code plug should be wired according to the table and the machine configuration.