C15 – Cruise Control, Idle, or PTO Can Not Be Set

Probable Causes

The probable root causes are listed below:
• Customer Specified Parameters (normal operation)
• Cruise Control Pause Switch
• On/Off switch for Cruise Control and Idle Control
• PTO On/Off Switch
• Set/Resume Switch
• Circuit for Service Brake Switch
• Transmission Neutral Switch Circuit
• Clutch Switch Circuit
• Vehicle Speed Circuit
• Adaptive Cruise Control

Recommended Actions
Perform the following diagnostic procedures in order:
1. When the Cruise Control or the Idle Control is set with the Cruise Control On/Off switch, use Cat ET in order to check the Configuration. Check the following parameters:
• “Low Cruise Control Set Speed Limit”
• “High Cruise Control Set Speed Limit”
• “Idle Vehicle Speed Limit”
• “Idle rpm Limit”

Note: If the vehicle speed exceeds the “High Cruise Control Set Speed Limit” and the driver attempts to set a cruise control speed, the cruise set speed will be the “High Cruise Control Set Speed Limit”. If the vehicle speed is below the “Low Cruise Control Set Speed Limit”, the Cruise Control can not be set or resumed. If the engine rpm is above the Idle rpm Limit and the driver attempts to set an Idle engine rpm the Idle engine rpm will be the Idle rpm Limit. If the driver attempts to set an Idle engine rpm and the vehicle speed exceeds the Idle Vehicle Speed Limit, the Idle will not activate. Refer to Troubleshooting, “Cruise Control Switch Circuit – Test”.

2. Connect Cat ET to the data link connector. Check the status screen for the following kickouts:

• Cruise Kickout

If the cruise control pause switch was the cause of the last kickout, the cruise control pause switch may be preventing normal operation of the cruise control.
a. Check the position of the cruise control pause switch. If the switch is in the ON position, the switch will prevent normal operation of the cruise control. Change the switch to the OFF position. Verify that the repair eliminates the problem.

b. If the cruise control pause switch is in the
OFF position and the switch is still causing
the cruise kickout, the switch is bad or the
wiring is shorted.

c. Check the switch for proper operation. If the switch is bad, replace the switch. If the switch is working, the wiring is probably shorted. Refer to Troubleshooting, “Electrical Connectors – Inspect”.

3. When the PTO is set with a dedicated PTO On/Off switch, use Cat ET to check the Configuration.
Check the following parameters:
• “PTO Configuration”
• “PTO Vehicle Speed Limit”
• “PTO Top Engine Limit”
• “PTO Cab Controls RPM Limit”
Refer to Troubleshooting, “PTO Switch Circuit – Test” for additional information.

4. Connect Cat ET to the data link connector. Check the Status Screen for the following controls:
• On/Off switch for Cruise Control and Idle Control

• PTO On/Off Switch
• Set/Resume Switch
• Circuit for Service Brake Switch
• Transmission Neutral Switch
• Clutch Switch
• Vehicle Speed

a. Turn on the On/Off switch for Cruise Control and Idle Control while the status screen on Cat ET is being viewed. The status screen should indicate that the switch is changing ON and OFF. If the problem is related to the On/Off switch for Cruise Control and Idle Control, refer to Troubleshooting, “Cruise
Control Switch Circuit – Test”.

b. Toggle the Set/Resume switch from SET to RESUME while the status screen on Cat ET is being viewed. The status screen should indicate that the switch is changing ON and OFF. If the problem is related to the Set/Resume switch, refer to Troubleshooting, “Cruise Control Switch Circuit – Test”.

c. Depress the Service Brake while the status screen on Cat ET is being viewed. The status screen should indicate that the pedal is being depressed or released. If the problem is related to the Service Brake switch, refer to Troubleshooting, “Service Brake Pedal Position (Switch 1) Circuit – Test”.

d. Depress the Clutch while the status screen on Cat ET is being viewed. The status screen should indicate that the pedal is being depressed or released. If the problem is related to the Clutch switch, refer to Troubleshooting, “Clutch Pedal Position Switch Circuit – Test”.

e. Shift the transmission to NEUTRAL while the status screen on Cat ET is being viewed.
The status screen should indicate that the transmission is being shifted to NEUTRAL.
If the problem is related to the Transmission Neutral Switch, refer to Troubleshooting, “Neutral Switch Circuit – Test”.

f. Check the vehicle speed while the vehicle is being driven in order to determine that the
vehicle speed that is indicated by Cat ET does not vary significantly from the vehicle speed that is indicated by the speedometer.
Possible root causes for problems with the vehicle speed circuit could be an incorrect Vehicle Speed Calibration or an intermittent speed signal. If the problem is not apparent, refer to Troubleshooting, “Vehicle Speed Circuit – Test”.

5. Check the Adaptive Cruise Control for proper operation.
a. Toggle the cruise control switch to the OFF position and to the ON position twice within
10 seconds. This will disable the Adaptive Cruise Control.
b. Attempt to set the cruise control. Operate the vehicle under the same conditions that
caused the problem.
c. If the problem still exists, then the problem is not the Adaptive Cruise Control.
d. If the problem is fixed, refer to Eaton for the proper troubleshooting procedure.

 

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