Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Underbody Component Corrosion (PI0281L)
Reference number: PI0281L
Supersedes refnos: PI0281, PI0281A, PI0281B, PI0281C, PI0281D, PI0281E, PI0281F, PI0281G, PI0281H, PI0281I, PI0281J, PI0281K
UNDERBODY COMPONENT CORROSION
TECHNICAL SERVICE BULLETIN
| Affected Model(s): | 2025 and Prior GM Passenger Cars and Trucks (Excluding Medium Duty Low Cab Forward) |
| Attention: | This PI also applies to any of the above models that may be Export from North America vehicles. |
| Supercedes: | This PI has been revised to add the 2025 Model Year. Please discard PI0281K. |
SERVICE INFORMATION
Service agents must comply with all International, Federal, State, Provincial, and/or Local laws applicable to the activities it performs under this bulletin, including but not limited to handling, deploying, preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you must follow those applicable laws.
The following information may be helpful when addressing underbody component corrosion with customers.
Some customers may comment that one or more of their vehicle's underbody components are showing some form of corrosion.
This corrosion may be red in appearance (rust) if the component is steel, forged iron or cast iron.
This corrosion may also be grey or white in color if the component is constructed of an aluminum alloy.
Extended outside storage may increase the opportunity for brake rotor rust. Vehicle braking systems tend to be self-cleaning while vehicles are in use, preventing any build-up of corrosion on the brake rotor surfaces. At times more extensive corrosion can cause pulsation due to thickness variation. This usually happens when the vehicle is parked for long periods of time in humid type conditions and the braking surface area under the pads corrode at a different rate compared to the rest of the braking surface area. Cleaning up of braking surfaces (burnishing) can be accomplished by 10-15 moderate stops from 56-64?km/h (35-40?mph) with cooling time between stops. If multiple, moderate braking stops do not correct this condition, refer to the following Service Bulletins for additional information:
- Latest version of Corporate Bulletin Number 00-05-22-002: BRAKE LATHE CALIBRATION PROCEDURE
- Bulletin # 22-NA-026: INFORMATION ON BRAKE PULSATION, NOISE AND/OR VISIBLE PITTING CONDITION TO BRAKE ROTOR SURFACE
- Bulletin # 17-NA-239: NORMAL CHARACTERISTIC - VEHICLE UNABLE TO MOVE AFTER BEING PARKED FOR AN EXTENDED PERIOD OF TIME
CORROSION PROTECTION
General Motors uses a large variety of materials in the manufacture of vehicles. Many of these components undergo an extensive corrosion protection process. These components include major body structures, powertrain, wiring and electrical components and various other areas of the vehicle. General Motors engineering determines the effects of corrosion on every vehicle component.
Acceptable Corrosion
General Motors has determined that the performance of some components is not affected by surface corrosion and no longer takes preventative steps on these parts.
Rust
This corrosion may be red or brown in appearance if the component is made of steel, forged iron or cast iron.
These are typical underbody or mechanical components such as but not limited to propshafts, propshaft yokes, U-joint, steering knuckles, brake rotors and calipers, axle housings, springs, shock absorbers, suspension control arms, tie rod ends and exhaust system components. As the rust ages, it turns from an orange-red like appearance to a darker brown like appearance.
Aluminum Oxidation
Cast aluminum alloy components may appear to have a grey or white coating on the surface commonly known as "surface oxidation." Uncoated aluminum alloys begin to oxidize as soon as it is exposed to the atmosphere. This coating does not affect the serviceability or performance of the component.
Many mechanical components are cast in aluminum alloys, these components may include, but are not limited to oil pans, valve covers, transmission and transfer case housings, steering gears and axle housings.
Typical Appearance
Front axle housing
Steering linkage
Steering knuckle
Tie rod end
Propshaft yoke
Leaf spring
Rear differential housing
Under hood components
Exhaust system components
During transit between the plant and the dealer, some of the exhaust system components may corrode as a result of salt exposure. These exhaust parts are made of a bare mild-grade stainless steel that will oxidize or appear rusty. Over time, these components will have a uniform rust-like discoloration, which should be considered a normal condition.
RECOMMENDATION
No repair or consideration should be given for this condition. Surface corrosion on unprotected components will vary with age and exposure. Corrosion on these components has no detrimental impacts, either in short or long-term durability.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.