2026 Peterbilt 536 TSBs

software with an incorrect variable. This software issue may cause DTC 521215-2 to set, the Transmission Dash Light to Illuminate, and shifting to be restricted. A software update is now available to fix the issue. Fix-as-Fail start date: 03/19/2025.

Control Unit (VECU) part number Q21-1157-013-011 / Q21-1157-013-013. Parts and procedures for Phase 2 chassis will be available at a later date. This bulletin will be updated at that time. Please refer to the condition section for more details. Certain Ethernet Multiplexed Architecture (EMUX) chassis fail to conform to Federal and Canada Motor Vehicle Safety Standards (FMVSS/CMVSS) No. 108. Delayed or unsteady illumination of the vehicles stop lamps, reverse lamps, turn signal lamps and inadvertent change in headlamp illumination or lift axle position may"

chassis may not function and can be reset only by a key cycle. This issue may result in non-compliance with US Federal Motor Vehicle Safety Standards (FMVSS) or Canadian Motor Vehicle Safety Standards (CMVSS) 101 and 108. This bulletin will be updated when software and programming procedures are available."

2 chassis added to the chassis list. Peterbilt: Dealers should check the chassis list and SIR weekly for VIN changes. 10 chassis added to the chassis list."

is no longer compatible.

part number Q21-1157-013-011 / Q21-1157-013-013 / Q21-1157-002-002 / Q21-1157-004-004 / Q21-1157-006-006 / Q21-1157-009-009. See attached Parts Matrix for required parts per chassis.

It must be used if safety recall 25PACF is performed prior to or at the same time as this repair since the 25PACF remedy also satisfies this safety recall.

and can be reset only by a key cycle. This issue may result in non-compliance with FMVSS/CMVSS 101 and 108. Affected chassis must have the Vehicle Soft ware updated.