Date Published: October 6, 2026 | 4 minute read | FAQ Article by Jill Tresch at Redwater Dodge

Mastering the Ram Truck High Idle Feature: How to Warm Up Your Diesel in Canadian Winters

What Is the Ram High Idle Feature and How Does It Work?

The high idle feature (also known as elevated idle or manual idle-up) allows the driver to manually increase the engine's idling speed from its standard baseline rate of approximately 650–700 RPM up to 1,000–1,500 RPM while the vehicle is stationary in Park.

On traditional trucks, elevating engine RPM required aftermarket tuners or manual throttle hand-cables. On modern Ram 2500 and 3500 trucks equipped with the 6.7L Cummins® Turbo Diesel, Stellantis engineers built this electronic control directly into the factory Powertrain Control Module (PCM).

Activating the feature is remarkably simple and requires no extra tools or aftermarket modifications:

1. Park the Vehicle: Ensure your Ram truck is turned on, running, and securely shifted into Park (or Neutral with the parking brake firmly set for manual models). Keep your foot completely off the brake pedal.
   
   
2. Turn On Cruise Control: Press the standard Cruise Control On/Off button located on the right side of your steering wheel. You will see the cruise control indicator icon light up on your digital gauge cluster.
   
   
3. Engage High Idle: Press the SET (or SET -) button on your steering wheel controls. The engine RPM will instantly ramp up from base idle to approximately 1,000 RPM.
   
   
4. Adjust Engine Speed (Optional): To increase the idle speed further for faster heating, press or hold the SET + / CANCEL / ACCEL steering wheel buttons to adjust the engine speed up to 1,500 RPM depending on model year programming.
   
   
5. Disengage High Idle: To return to standard idle, simply tap the foot brake pedal, turn off the master Cruise Control switch, or shift out of Park. The engine instantly drops back to standard idling RPM.

Why High Idling Is Critical for Diesel Engines in Cold Climates

Allowing a heavy-duty diesel engine to sit at low base idle for extended periods during cold Canadian winter weather can cause long-term mechanical damage. Diesel engines generate heat through fuel compression rather than spark ignition. In extreme cold, low RPM idling allows combustion chamber temperatures to drop significantly below optimal operating thresholds.

Operating a diesel at low ambient temperatures causes several severe mechanical issues:

"Wet Stacking" and Fuel Dilution: When combustion chamber temperatures drop during low idle, diesel fuel fails to burn completely. Unburnt fuel coats the cylinder walls, washing away protective engine oil film (cylinder wash) and seeping past piston rings into the oil pan, diluting engine oil.

Diesel Particulate Filter (DPF) Clogging: Incomplete combustion produces excessive soot and carbon build-up, rapidly clogging the exhaust DPF system and forcing frequent, fuel-heavy active regeneration cycles.

Cabin Heater Efficiency: At base idle in -20°C weather, a diesel engine cannot generate enough heat to warm the engine coolant. High idling circulates hot coolant through the heater core much faster, delivering rapid cabin defrosting and interior warmth.

Frequently Asked Questions

Q1. Does the Cruise Control high idle trick work on Ram trucks with HEMI® gas engines?

A1. No. The steering wheel Cruise Control high idle activation method is designed specifically for Ram heavy-duty trucks equipped with the 6.7L Cummins® Turbo Diesel engine. Gas-powered HEMI® models utilize automated electronic throttle control to temporarily adjust idle speed based on ambient temperature sensors upon cold startup.

Q2. Will using high idle consume significantly more fuel during winter warm-ups?

A2. While high idling uses slightly more fuel per minute than base idling, it gets the engine up to efficient operating temperature dramatically faster. Operating an engine at proper temperature reduces overall engine wear, cuts down on soot generation, and avoids fuel-wasting active DPF regenerations, making it far more efficient in the long run.

Q3. Why won't my high idle engage when I press Cruise Control and SET?

A3. If your high idle fails to engage, ensure your foot is completely off the brake pedal, the truck is fully shifted into Park (or Neutral with the parking brake set), and the master Cruise Control switch is turned ON first. If the brake pedal sensor detects pressure, the PCM automatically disables high idle for safety reasons.

Q4. Does high idle engage automatically during Remote Start in cold weather?

A4. Yes. Modern Ram 2500 and 3500 models feature an automatic ambient temperature sensor that elevates engine RPM during remote start if outside temperatures drop below freezing. However, manually using the Cruise Control method gives you full manual control over engine RPM once you enter the cab.