If the vehicle is equipped with this feature, there is an exhaust restrictor valve located in the exhaust stream. The valve closes to provide back pressure to the engine for the purpose of warming the engine quickly.
The exhaust restrictor operates:
| • | while the engine is running. |
| • | while the vehicle is not moving. |
| • | while the accelerator, brake and clutch pedals are not pressed on a manual transmission vehicle. |
| • | while idling in cold temperatures. |
| • | when the shifter is in N (Neutral) or P (Park) on an automatic transmission vehicle. |
On vehicles equipped with a diesel engine exhaust brake, the exhaust brake switch must be on. See Diesel Engine Exhaust Brakefor more information. The indicator in the exhaust brake switch will be lit when the exhaust restrictor is active. The exhaust brake indicator light in the center of the instrument panel will also be lit whenever the exhaust restrictor is active. See Exhaust Brake Indicator Light for more information.
When the engine coolant temperature is below 149°F (65°C) and the outside temperature is below 50°F (10°C), the exhaust restrictor will come on within 60 seconds of starting the engine. After running the engine for an additional 10 seconds, the engine idle will increase.
The exhaust restrictor will shut off and engine idle will return to normal once the engine is warmed up, or the brake pedal is pressed.
