Service bulletin 19-TR-19EN

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

NHTSA's summary

Service tip for the optional Preselect Optimization feature. The transmission will not initiate preselect downshifts when the engine brake is active, unless the service brake is simultaneously depressed. Correction: If closed throttle Engine Brake Preselect downshifts without depressing service brake are desired, then the ENGINE BRAKE: Automatic Preselect Optimization (CMC) setting must be changed to NONE using the reprogramming function in Allison DOC® (see Figure 1). The TCM will revert to the defined Engine Brake Interface, Input H / Output A or Input I / Output A parameters. The Engine Brake Automatic Preselect Optimization logic will be disabled. Grade Braking Automatic Preselect Optimization and Cruise Control Preselect Optimization will be unaffected

The document

• NHTSA's copy of the document (PDF)
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The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Electrical system, Software

Listing a model year does not mean every vehicle of it is concerned: the document says which.

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