C7.1 Engines and Generator Sets Caterpillar

Throttle Lock - Test

Usage:

C7.1 770

Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:

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Table 1
Diagnostic Trouble Codes
J1939 Code	CDL Code	Code Description	Comments
-	549-2	Throttle Lock Enable Switch : Erratic, Intermittent, or Incorrect	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.
-	549-3	Throttle Lock Enable Switch : Voltage Above Normal	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.
-	549-4	Throttle Lock Enable Switch : Voltage Below Normal	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.
-	2770-3	Throttle Lock Resume/Decel Switch : Voltage Above Normal	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.
-	2770-4	Throttle Lock Resume/Decel Switch : Voltage Below Normal	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.
-	2771-3	Throttle Lock Set/Accel Switch : Voltage Above Normal	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.
-	2771-4	Throttle Lock Set/Accel Switch : Voltage Below Normal	The code is logged. The ECM will disable the automatic control of engine speed through the throttle hold feature and the throttle lock feature.

The throttle lock feature is activated by using the throttle lock switch and the "throttle lock set/accel switch". Use the throttle lock switch to maintain a desired engine speed. The throttle lock switch is a three-position rocker switch that is used to select the mode of operation. The "throttle lock set/accel switch" is a two-position momentary rocker switch. This switch is for setting the engine speed and/or adjusting the engine speed. The throttle lock feature has the following three modes of operation:

Automatic mode
Manual mode
OFF

The following features apply to both the "Automatic Mode" and "Manual Mode:"

Acceleration - Moving the "Throttle Lock Set/Accel Switch" in the forward direction (SET/ACCEL) will increase the desired engine speed. Momentarily bumping the "Throttle Lock Set/Accel Switch" will increase the desired engine speed by 100 rpm. Holding the "Throttle Lock Set/Accel Switch" for more than 250 ms will increase the desired engine speed at a rate of 700 rpm per second. Moving the throttle pedal past the engine speed setpoint will increase the engine speed. Releasing the throttle pedal will allow the engine speed to return to the locked engine speed.

Deceleration - Moving the "Throttle Lock Resume/Decel Switch" (RESUME/DECEL) on the joystick will decrease the desired engine speed. Momentarily bumping the "Throttle Lock Resume/Decel Switch" will decrease the desired engine speed by 100 rpm. Holding the "Throttle Lock Resume/Decel Switch" for more than 250 ms will decrease the desired engine speed at a rate of 700 rpm per second.

Note: Actual engine speed may ramp at a slower rate than desired engine speed. The "Throttle Lock Set/Accel Switch" and the "Throttle Lock Resume/Decel Switch" control desired engine speed. For example, if you bump the "Throttle Lock Set/Accel Switch" five times, desired engine speed will immediately increase by 500 rpm. Actual engine speed may not react quickly if the engine is under load.

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Automatic Mode

Depress the throttle lock switch in the forward direction to the AUTO position to select the automatic mode. Use the throttle pedal to achieve the desired engine speed. Then depress the "Throttle Lock Set/Accel Switch" in the forward direction (SET/ACCEL) to set the desired engine speed.

Automatic Mode ("Throttle Lock Kickout") - If the throttle lock feature is enabled and active, any of the following actions will cancel the throttle lock.

Applying the service brake will suspend the selected engine speed and the engine will decelerate at a rate of 700 rpm per second. The engine will decelerate until the engine speed matches the desired engine speed for the throttle pedal position.
After the throttle pedal is less than 10 percent, depressing the throttle pedal to more than 25 percent will suspend the selected engine speed. The engine speed will then change at a rate of 700 rpm per second. The engine speed will change until the engine speed relates to the position of the throttle pedal.
The operator moves the throttle lock switch to the OFF position.

The suspended engine speed may be resumed if none of the following actions have occurred:

The throttle lock switch is moved to the OFF position.
The keyswitch is turned to the OFF position.
The engine stalls.

Manual Mode

Depress the throttle lock switch in the backward direction to the MAN position to select the manual mode. Use the throttle pedal to achieve the desired engine speed. Then depress the "Throttle Lock Set/Accel Switch" in the forward direction (SET/ACCEL) to set the desired engine speed.

Manual Mode ("Throttle Lock Kickout") - If the throttle lock feature is enabled and active, moving the throttle lock switch to the OFF position will cancel the throttle lock.

OFF

When the throttle lock switch is in the OFF (center) position, the throttle lock feature is disabled. The throttle pedal will then be the only means of controlling engine speed.

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Illustration 1	g02073456
Throttle lock switch (Terminal 1) "Throttle lock switch (MAN)" (Terminal 2) Digital return (Terminal 3) "Throttle lock switch (OFF)" (Terminal 5) Digital return (Terminal 6) "Throttle lock switch (AUTO)"

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Illustration 2	g02073457
"Throttle lock set/accel switch" (Terminal 1) "Throttle lock set/accel switch (N/C)" (Terminal 2) Digital return (Terminal 3) "Throttle lock set/accel switch (N/O)"

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Illustration 3	g02073459
P2 connector for the proportional joystick (Terminal 2) "Throttle lock resume/decel switch (N/O)" (Terminal 3) "Throttle lock resume/decel switch (N/C)"

During the following procedure, refer to the electrical schematic for the application.

Complete the procedure in the order in which the steps are listed.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Turn the keyswitch to the OFF position. B. Thoroughly inspect the J1/P1 connectors on the Electronic Control Module (ECM), the switch connections and battery connections. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires in the switch connectors and the ECM connector that are associated with the fault. D. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in). E. Check the harness for corrosion, abrasion, and pinch points from the PTO mode switches to the ECM.	Loose connection or damaged wire	Result: There is a fault in a connector or the wiring. Repair: Repair any faulty connectors or replace the wiring harness. Ensure that all the seals are properly in place and ensure that the connectors are correctly coupled. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. Proceed to Test Step 2.
2. Check for Diagnostic Codes A. Turn the keyswitch to the OFF position. B. Connect the electronic service tool to the diagnostic connector. C. Turn the keyswitch to the ON position. D. Monitor the electronic service tool for active diagnostic codes and/or logged diagnostic codes.	Diagnostic codes	Result: No diagnostic code is active. The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Result: A 549-2, 549-3 or 549-4 diagnostic code is active. Proceed to Test Step 3. Result: A 2770-3 or 2770-4 diagnostic code is active. Proceed to Test Step 5. Result: A 2771-3 or 2771-4 diagnostic code is active. Proceed to Test Step 7.
3. Check the Status of the Throttle Lock Switch A. Turn the keyswitch to the ON position. B. Move the throttle lock switch to the AUTO position and observe the status of the "Throttle Lock Switch" on the electronic service tool. The status should be "On". C. Move the throttle lock switch to the MAN position and observe the status of the "Throttle Lock Switch" on the electronic service tool. The status should be "On". D. Move the throttle lock switch to the OFF position and observe the status of the "Throttle Lock Switch" on the electronic service tool. The status should be "Off".	Throttle lock switch status	Result: The status changes as the switch position is changed. The throttle lock switch appears to be operating correctly. Repair: The fault may be intermittent. If the fault is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Result: There is a fault in the circuit for the throttle lock switch. Proceed to Test Step 4.
4. Create a Short at the Throttle Lock Switch A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the throttle lock switch. C. Install a jumper wire between terminal 5 (return) and terminal 6 (throttle lock switch (AUTO)) on the wiring harness connector for the throttle lock switch. D. Turn the keyswitch to the ON position. E. Observe the status of the Throttle Lock Switch on the electronic service tool. The status should be "On". F. Turn the keyswitch to the OFF position. G. Install the jumper wire between terminal 2 (return) and terminal 1 (throttle lock switch (MAN)) on the wiring harness connector for the throttle lock switch. H. Turn the keyswitch to the ON position. I. Observe the status of the Throttle Lock Switch on the electronic service tool. The status should be "On". J. Turn the keyswitch to the OFF position. K. Install the jumper wire between terminal 2 (return) and terminal 3 (throttle lock switch (OFF)) on the wiring harness connector for the throttle lock switch. L. Turn the keyswitch to the ON position. M. Observe the status of the Throttle Lock Switch on the electronic service tool. The status should be "Off". N. Turn the keyswitch to the OFF position. O. Remove the jumper wire and reconnect the switch.	Switch status	Result: The status changes as the respective terminals are shorted. The ECM and the wiring harness are functioning correctly. Repair: Replace the throttle lock switch. Verify that the repair eliminates the fault. Result: The status does not change as the respective terminals are shorted. There is a fault in the circuit between the ECM and the throttle lock switch. Repair: Repair the harness wiring or replace the harness. Verify that the repair eliminates the fault.
5. Check the Status of the Throttle Lock Resume/Decel Switch A. Observe the status of "Throttle Lock Resume/Decel Switch Position" on the electronic service tool. The status should be "On".	Switch status changes when jumper is installed	Result: The status changes as the switch position is changed. The Throttle Lock Resume/Decel Switch is operating correctly. Repair: The fault may be intermittent. If the fault is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Result: The status does not change as the switch position is changed. There is a fault in the circuit for the Throttle Lock Resume/Decel Switch. Proceed to Test Step 6.
6. Create a Short at the Throttle Lock Resume/Decel Switch A. Turn the keyswitch to the OFF position. B. Disconnect the P2 connector for the Throttle Lock Resume/Decel Switch"". C. Install a jumper wire between engine ground and terminal P2-3 (throttle lock resume/decel switch (N/C)) on the Throttle Lock Resume/Decel Switch harness connector. D. Turn the keyswitch to the ON position. E. Observe the status of the "Throttle Lock Resume/Decel Switch Position" on the electronic service tool. The status should be "Off". F. Turn the keyswitch to the OFF position. G. Install a jumper wire between engine ground and terminal P2:2 (throttle lock resume/decel switch (N/O)) on the Throttle Lock Resume/Decel Switch harness connector. H. Turn the keyswitch to the ON position. I. Observe the status of "Throttle Lock Resume/Decel Switch Position" on the electronic service tool. The status should be "On". J. Turn the keyswitch to the OFF position. K. Remove the jumper wire and reconnect the connector for the Throttle Lock Resume/Decel Switch.	Switch status changes when jumper is installed	Result: The status changes as the respective terminals are shorted. The ECM and the wiring harness are functioning correctly. Repair: Replace the Throttle Lock Resume/Decel Switch. Verify that the repair eliminates the fault. Result:The status does not change as the respective terminals are shorted. There is a fault in the circuit between the ECM and the Throttle Lock Resume/Decel Switch. Repair: Repair the harness wiring or replace the harness. Verify that the fault is resolved.
7. Check the Status of the Throttle Lock Set/Accel Switch A. Observe the status of "Throttle Lock Set/Accel Switch Position" on the electronic service tool. The status should be "Off". B. Hold the Throttle Lock Set/Accel Switch in the SET/ACCEL position and observe the status of "Throttle Lock Set/Accel Switch Position" on the electronic service tool. The status should be "On".	Switch status	Result: The status changes as the switch position is changed. The Throttle Lock Set/Accel Switch appears to be operating correctly. Repair: The fault may be intermittent. If the fault is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Result:The status does not change as the switch position is changed. There is a fault in the circuit for the Throttle Lock Set/Accel Switch. Proceed to Test Step 8.
8. Short the Wires at the Throttle Lock Set/Accel Switch A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the Throttle Lock Set/Accel Switch. C. Install a jumper wire between terminal 2 (return) and terminal 3 (throttle lock set/accel switch (N/O)) on the Throttle Lock Set/Accel Switch harness connector. D. Turn the keyswitch to the ON position. E. Observe the status of the "Throttle Lock Set/Accel Switch Position" on the electronic service tool. The status should be "Off". F. Turn the keyswitch to the OFF position. G. Install a jumper wire between terminal 2 (return) and terminal 1 (throttle lock set/accel switch (N/C)) on the Throttle Lock Set/Accel Switch harness connector. H. Turn the keyswitch to the ON position. I. Observe the status of "Throttle Lock Set/Accel Switch Position" on the electronic service tool. The status should be "On". J. Turn the keyswitch to the ON position. K. Remove the jumper wire and reconnect the connector for the Throttle Lock Set/Accel Switch.	Switch status changes when jumper is installed	Result: The status changes as the respective terminals are shorted. The ECM and the wiring harness are functioning correctly. Repair: Replace the Throttle Lock Set/Accel Switch. Verify that the repair eliminates the fault. Result:The status does not change as the respective terminals are shorted. There is a fault in the circuit between the ECM and the Throttle Lock Set/Accel Switch. Repair: Repair the harness wiring or replace the harness. Verify that the fault is resolved. If the fault is still present, contact the Dealer Solutions Network (DSN).