FAW Front Underbody Protection Logic Assembly: Deconstructing the 29 Critical Components

Welcome to this critical technical guide on the FAW Front Underbody Protection Logic Assembly. This is the complete “FUPD” (Front Underrun Protection Device) system for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This is not an optional or cosmetic part; it is a critical, chassis-mounted safety and structural component.

The FAW Front Underbody Protection Logic Assembly is a heavy-duty, engineered steel structure. Its primary “logic” is to provide a low, rigid barrier at the very front of the truck. This system is mandated by safety regulations (like ECE R93) to prevent smaller vehicles from “under-running” (sliding under) the high chassis of the tractor in a frontal collision. It is designed to engage the other vehicle’s crumple zones.

This in-depth guide is an essential resource for professional body shop technicians, fleet managers, and parts specialists. We will deconstruct the entire FAW Front Underbody Protection Logic Assembly into its 29 serviceable components (total quantity of parts listed), including the main ‘Crossmember’ (2802070-91W), the ‘Left Brackets’ (2802021-91W), and all the critical high-tensile fasteners that secure this safety device.

Core Component: The Main Crossmember (2802070-91W)

The heart of the FAW Front Underbody Protection Logic Assembly is the ‘Front underbody protection crossmember welded assy’ (2802070-91W). This is the main horizontal “beam” or “bar” of the system. It is a massive, heavy-gauge steel fabrication, likely a C-channel or box-section, designed for one purpose: to absorb and transfer impact energy.

This component is the “logic” of the FUPD system. In a frontal collision with a smaller vehicle, this crossmember is the primary point of contact. It is engineered to be extremely strong, preventing the smaller vehicle from going *under* the truck frame and directly impacting the front axle, steering gear, or engine. This crossmember is the core of the FAW Front Underbody Protection Logic Assembly‘s strength.

The “welded assy” designation signifies that it is a multi-piece fabrication, robotically welded for consistent strength and quality. It is made from high-strength low-alloy (HSLA) steel, which is designed to deform in a controlled manner under a severe impact, absorbing energy rather than shattering. This controlled deformation protects the truck’s main frame rails from being bent, which would total the vehicle. A bent or cracked crossmember in the FAW Front Underbody Protection Logic Assembly must be replaced immediately.

The “Brackets”: Chassis Connection (2802021-91W)

If the crossmember is the “shield,” the ‘Front underbody protection left bracket’ (2802021-91W) units are the “arms” that hold it. These are the critical, high-strength structural components of the FAW Front Underbody Protection Logic Assembly. The parts list calls for two, which are the left-hand and right-hand symmetrical brackets.

These are the “bones” of the system, forged or fabricated from thick, high-strength steel plate. Their function is to connect the entire FAW Front Underbody Protection Logic Assembly to the main chassis frame rails of the truck. They are the “logic” that transfers impact forces *away* from the bumper and *into* the vehicle’s frame, which is designed to handle them.

These brackets are not designed to be a “crumple zone”; they are designed to be an unyielding, rigid link. They are bolted to the front “horns” or “flanges” of the truck’s main C-channel frame, often sharing bolt holes with the front spring hangers or tow hooks. This ensures the FAW Front Underbody Protection Logic Assembly is anchored to the strongest part of the truck.

These brackets also provide the primary alignment points. A minor bend in one of these brackets, while not always visible, will cause the entire FAW Front Underbody Protection Logic Assembly (and the cosmetic bumper that mounts to it) to appear crooked, with uneven gaps. A misaligned assembly is a sign of compromised safety, as the impact-transfer logic is now flawed.

The Fastener System: High-Tensile Hardware

A safety system like the FAW Front Underbody Protection Logic Assembly is only as strong as its fasteners. This assembly is held together by a specific set of 26 high-tensile bolts and washers designed to withstand extreme shear and vibrational forces.

**1. ‘Hex head bolt’ (CQ1501240T) – 8 units:** These are the primary structural bolts. The “T” suffix indicates a high-tensile strength class (e.g., 10.9) and a specialized coating. These 8 bolts are likely used to connect the ‘Crossmember’ (2802070-91W) to the two ‘Brackets’ (2802021-91W).

**2. ‘Hex head flange bolt’ (Q1851440T) – 10 units:** These are the secondary structural bolts. The “flange” head acts as an integrated, wide-area washer. This is critical for spreading the clamping load on the chassis rail, preventing the bolt from “pulling through” the steel frame under extreme force. These 10 bolts are almost certainly the ones used to secure the two ‘Brackets’ directly to the truck’s main chassis frame rails.

**3. ‘Spring gasket’ (Q40312) – 8 units:** These are critical “lock washers.” They are paired with the ‘Hex head bolts’ (CQ1501240T). Their function is to exert constant spring tension on the bolt head, physically preventing the bolt from vibrating loose. In a high-vibration environment like a truck chassis, a standard washer would be useless, and the bolts would quickly fail. The total hardware package for the FAW Front Underbody Protection Logic Assembly is robust.

This fastener “logic” is a key part of the FAW Front Underbody Protection Logic Assembly. Using non-specified, lower-grade bolts (e.g., a standard Class 8.8) from a hardware store would compromise the entire safety system, as they would shear off or vibrate loose, causing the FUPD to fail during an impact. Inspecting the FAW Front Underbody Protection Logic Assembly includes checking these bolts.

FAW Front Underbody Protection Logic Assembly Parts List

The following table provides the complete, detailed breakdown of all 29 components identified in the ‘Front Underbody Protection Logic Assembly’ diagram for the FAW CA4251P66K24T1A3E5 tractor. This FAW Front Underbody Protection Logic Assembly is a critical safety-of-life component.

Technical Specifications and Assembly Context

The specifications for the FAW Front Underbody Protection Logic Assembly are defined by its function as a heavy-duty, chassis-mounted safety system. The FAW Front Underbody Protection Logic Assembly is a non-optional, safety-critical system.