There are two distinct ways to engage a high idle on a Cummins engine, often leading to confusion. Let’s clarify the differences between these two methods:
Automatic High Idle (Cold Weather)
Cummins engines, particularly in the third generation (Gen 3), have an automatic high idle feature activated by cold temperatures. When the outside temperature and engine are sufficiently cold, the Engine Control Module (ECM) automatically increases engine RPM to around 1000. This function aids in warming the engine more quickly. Importantly, this automatic high idle is not user-controlled; it cannot be adjusted or activated through the cruise control buttons.
PTO High Idle (User-Controlled)
Gen 3 Cummins engines (generally from 2004 onwards, with some late 2003 models potentially included) offer a second high idle function related to the Power Take-Off (PTO). Unlike the automatic cold weather high idle, the PTO high idle must be enabled in the ECM. This can be done by a Cummins dealer using a StarScan tool, by someone with a compatible diagnostic scanner, or with a programmer like Smarty.
Once enabled, the PTO high idle is controlled through the cruise control buttons. You can adjust the idle speed between 1100 and 1500 RPM. This feature is useful for various purposes, including:
- Warming up the engine faster in cold conditions.
- Powering accessories like air conditioning in hot weather.
- Operating equipment connected to the PTO.
Enabling the PTO High Idle
Enabling the PTO high idle typically requires a dealer visit or someone with the necessary diagnostic equipment. Dealerships may charge varying fees for this service, ranging from no charge to around $85. Alternatively, certain aftermarket programmers can enable this feature.
Important Considerations for Manual Transmissions
Enabling the PTO high idle function involves additional steps for vehicles with manual transmissions:
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5.9L Cummins with Manual Transmission: In addition to enabling the feature in the ECM, you must ground pin #22 on the ECM.
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6.7L Cummins with Manual Transmission: Grounding a specific wire under the steering column is required. Consult online forums or resources for detailed instructions on locating and grounding the correct wire.
Controlling PTO High Idle with Cruise Control
After enabling the PTO high idle and completing any necessary grounding procedures, you can control the high idle using these steps:
- Press the “Cruise On” button.
- Press the “Set” button. This initially sets the high idle to 1100 RPM.
- Use the “Accel” and “Decel” buttons to adjust the idle speed between 1100 and 1500 RPM.
Aftermarket Programmers for Enabling PTO High Idle
Several aftermarket programmers can enable the PTO high idle feature:
- Smarty
- Bully Dog
- DiabloSport
Conclusion
Understanding the difference between the automatic cold weather high idle and the user-controlled PTO high idle is crucial for Cummins owners. The PTO high idle offers valuable functionality for various applications, and while enabling it might require some effort, the benefits can be significant. Remember to consult your owner’s manual or a qualified technician for specific instructions related to your Cummins engine model and transmission type.
