Ms. Stefanie Siverly
4700 Broadmoor SE, Suite 200
Grand Rapids, MI 49512
Dear Ms. Siverly:
This responds to your letter requesting an interpretation of whether aftermarket tire pressure monitoring systems (TPMS) would be subject to the requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 138, Tire pressure monitoring systems. I apologize for the delay in responding.
You state that your company is a testing laboratory and that you have a client who is distributing TPMS as an aftermarket item. Specifically, you state that your client produces both mechanical systems (where the vehicle operator would look at a gauge installed on the tire stem) and electronic systems (where there is a device which can be mounted or stored in the vehicle which alerts the operator to low pressure). Based on the information you have provided and the analysis below, we have concluded that the aftermarket products you describe would not directly be subject to FMVSS No. 138. However, if these aftermarket TPMS devices are installed on vehicles already equipped with TPMS, installation of the devices could be subject to the statutory prohibition against making items of motor vehicle safety equipment inoperative.
By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approvals of motor vehicles or motor vehicle equipment. Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture. NHTSA selects a sampling of new vehicles and equipment each year to determine their compliance with applicable FMVSSs. If our testing or examination reveals an apparent noncompliance, we may require the manufacturer to remedy the noncompliance, and may initiate an enforcement proceeding, if necessary, to ensure that the manufacturer takes appropriate action.
As noted above, some FMVSSs apply to motor vehicles, some apply to motor vehicle equipment, and some apply to both. FMVSS No. 138 is a vehicle standard, specifying performance requirements for tire pressure monitoring systems on new vehicles. The standard does not apply to aftermarket TPMS. However, there are several provisions of the National Traffic and Motor Vehicle Safety Act (49 U.S.C. 30101 et seq., the Safety Act) that have a bearing the manufacture and sale of aftermarket TPMS.
First, 30122(b) of the Safety Act states, in relevant part:
Prohibition. A manufacturer, distributor, dealer, or motor vehicle repair business may not knowingly make inoperative any part of a device or element of design installed on or in a motor vehicle or motor vehicle equipment in compliance with an applicable motor vehicle safety standard.
In general, this section prohibits the entities listed in 30122 from removing, disabling or otherwise making inoperative any of the safety systems or devices installed on the vehicle to comply with a safety standard. Therefore, the question of whether installation of an aftermarket TPMS violates the render inoperative prohibition is linked to whether the vehicle in which the aftermarket TPMS is being installed originally was subject to FMVSS No. 138. (We assume the modification of the vehicle is by an entity listed in 30122.)
If the vehicle in which the aftermarket TPMS is being installed was not originally certified as meeting FMVSS No. 138, under our regulations the aftermarket TPMS could be installed without regard to FMVSS No. 138 requirements. On the other hand, if a compliant TPMS that had been installed in the vehicle in compliance with FMVSS No. 138 were removed and replaced by the aftermarket TPMS, the removal of the compliant TPMS would violate the render inoperative prohibition unless the vehicle, as equipped with the aftermarket TPMS, meets the performance requirements of FMVSS No. 138.
The second provision of our safety statute of which you should be aware relates to the responsibilities of motor vehicle equipment manufacturers to ensure that their products are free of safety-related defects. An aftermarket TPMS is an item of motor vehicle equipment. Manufacturers of motor vehicle equipment are subject to the requirements in sections 30118-30122 of Title 49 of the U.S. Code concerning the recall and remedy of products with defects related to motor vehicle safety. If a manufacturer or NHTSA determines that an item of motor vehicle equipment contains a safety-related defect, the manufacturer would be responsible for notifying purchasers of the defective equipment and remedying the problem free of charge.
I hope this information is helpful. If you have any further questions, please do not hesitate to contact Rebecca Yoon of my staff at (202) 366-2992.
Stephen P. Wood
Acting Chief Counsel
 S2, Application, of the TPMS standard states that This standard applies to passenger cars, multipurpose passenger vehicles, trucks, and buses that have a gross vehicle weight rating of 4,536 kilograms (10,000 pounds) or less, except those vehicles with dual wheels on an axle, according to the phase-in schedule specified in S7 of this standard. 49 CFR 571.138.