C13 and C15 On-highway Engines Caterpillar

Probable Causes

This condition may be normal operation. One of the following features may be causing the elevated idle:

• Active regeneration

• Low battery voltage

• Warm-up mode

• PTO operation

Conditions

Active Regeneration

The Engine Control Module (ECM) slightly elevates the idle speed during an active regeneration at zero vehicle speed.

If the ECM is controlling the cooling fan, the cooling fan is turned on during the active regeneration.

Low Battery Voltage

Engine speed increases to the value that is programmed into the "Battery Monitor Low Idle Engine Speed" parameter when all of the following conditions exist:

• The vehicle is stopped.

• The transmission is not in gear.

• The brake pedal is not depressed.

• The clutch pedal is not depressed.

• System battery voltage is less than the value that is programmed into the "Battery Monitor & Engine Control Voltage" parameter for 30 seconds.

Warm-Up Mode

Engine speed increases to the value that is programmed into the "Warm Up Mode Idle Speed" parameter when all of the following conditions exist:

• The vehicle is stopped.

• The transmission is not in gear.

• The brake pedal is not depressed.

• The clutch pedal is not depressed.

• The sum of the coolant temperature and inlet manifold air temperature is less than 30 °C (86 °F).

PTO Operation

Engine speed may be elevated during PTO operation. Check the value of the "PTO Engine RPM Set Speed" parameter.