General Motors Duramax Diesel fuel - LLY: Transmission Fast Idle Organization

ATG Inc.

ATG Inc.

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Published Aug 23, 2016

The Duramax LLY engine has a manual fast idle organisation that can exist implemented by the operator to shorten warm up time when the engine is common cold. The ECM increases the idle speed by irresolute fuel injector timing and quantity, and the turbo charger vanes are commanded closed (extra boost).

The instrument panel will bespeak the high idle organization is active depending on the vehicle:

  • Lite Duty: The Commuter Info. Center (DIC) will indicate an active high idle system.
  • Medium Duty: An indicator lamp will flash on.


When activated, the ECM increases idle speed. To enable the system:

  1. Plow the ignition on with the engine off
  2. Depress the accelerator pedal to the floor and agree downward
  3. With the accelerator held down, press the brake pedal 3 times
  4. Release the accelerator pedal and outset the engine

When the procedure is followed, the engine idle speed volition slowly increase to the calibrated loftier idle speed, (1200 rpm for Lite-Duty, 1500 rpm for Medium-Duty). The fast idle system volition shut down and idle normally if the post-obit occurs:

  1. Stride on the brake clutch or accelerator pedals
  2. Shift the Automatic transmission out of PARK or NEUTRAL
  3. The air temperature is more than 0º C (32º F)
  4. The engine coolant temperature (is more than 68º C (154º F)
  5. The vehicle speed exceeds 0 mph (0 km/h)
  6. The engine is shut off

The high idle system volition reactivate automatically when the post-obit conditions occur:

  1. The engine has been idling for more 30 seconds
  2. The transmission is placed in PARK or NEUTRAL
  3. The vehicle speed is 0 mph (0 km/h)
  4. The ambient air temperature is less than 0º C (32º F)
  5. The engine coolant temperature is less than 68º C (154º F)
  6. The brake, clutch and throttle pedals are not depressed

T hese excerpts are from our 200-350 page manuals and may perhaps refer to data from other sections of the transmission or graphics / pictures. Our manuals comprise in-depth procedures that require screen shots of parts, charts and diverse graphs - likewise as detailed steps that guide you through troubleshooting existent-world automotive repair problems methodically for a quicker resolution.

For additional information on how to obtain the manuals that these tips come from, please refer to the products folio on our website:
www.atgtraining.com - yous will besides find trouble code handbooks likewise as DVD's on our more popular subjects.

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