High Idle System
The diesel engine has two possible high idle systems to improve the warm-up
time of the engine in cold weather conditions:
| • | An automatic high idle system. |
| • | A manual high idle system (if equipped). |
Both systems use the exhaust brake hardware to restrict exhaust gas flow. If
the exhaust brake hardware does not activate during the high idle system operation,
go to
Symptoms - Engine Exhaust Brake
in Engine Exhaust.
Automatic High Idle System
The automatic system will engage when the vehicle is started and the engine
is below the preset operating temperature. The ECM controls the activation of the
exhaust brake (if equipped) and raises idle speed to a calibrated level.
The automatic high idle system consists of the following components:
| • | The engine control module (ECM). |
The idle speed will return to normal if any of the following conditions occur:
| • | The engine reaches the preset operating temperature. |
| • | The engine has been operating for at least ten minutes. |
| • | The brake pedal is depressed. |
| • | The manual clutch pedal is pressed or the automatic transmission is shifted
from Park or Neutral. |
| • | The vehicle exceeds 5 MPH (8 km/h). |
| • | The throttle is pressed. |
Manual High Idle System
The manual high idle system will raise the engine idle speed to 1200 RPM
regardless of ambient or engine coolant temperatures. The manual high idle feature
is activated and can be deactivated by pressing the switch on the instrument panel.
The ECM controls the idle speed and exhaust brake restrictor (if equipped) to activate
the high idle when requested through the switch.
The manual high idle system consists of the following components:
| • | The engine control module (ECM) |
| • | A manual switch on the instrument panel. Refer to the owners manual. |
When any of the following conditions occur the manual high idle system will
be deactivated:
| • | The brake pedal is depressed. |
| • | The manual clutch pedal is pressed or the automatic transmission is shifted
from Park or Neutral. |
| • | The vehicle exceeds 5 MPH (8 km/h). |
| • | The throttle is pressed. |
