Manufacturers losing chip that powers ABS warning lamps

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The chip used to activate in-cab trailer ABS malfunction lamps has been discontinued, leaving suppliers with a limited three- to four-year “inventory bridge” to redesign and requalify their electronic control units.

The PLC-4-Truck P485 chip transmits the malfunction signal from the trailer ABS to the tractor, Commercial Vehicle Brake Manufacturers Council chairman Dave Engelbert said in a written notice. And that light is required under Federal Motor Vehicle Safety Standard 121.

But final orders for a share of the remaining chips need to be placed by Jan. 20.

ABS lamp
(Photo: istock)

Stocking three to four years of chips comes with its own risks, Engelbert said, referring to limited shelf lives. Those that can’t be used within three years need to be vacuum-sealed. Even then they last only five years.

“Inventories can also be destroyed by natural disasters, fires, or just lost in shipment — all possible threats that will impact the supply base ability to supply ABS ECUs to tractor and trailer OEMs and service replacement parts to the aftermarket during this three- to four-year transition,” he added.

Risks and limited experience

While another chip will support the PLC4Trucks/J2497 communication protocol, it has a different footprint than the P485 chip.

“There is also risk associated with the chip because none of the ABS suppliers have experience with the chip in current ABS ECU production products,” Engelbert said.

“The redesign and requalifying of current production of ABS ECUs will take time and rob resources from new product development to support redesign and requalifying of current production.” 

Replacement parts destined for the aftermarket will also need to be redesigned and requalified, he said. For some suppliers, that can mean redesigning six or more ABS ECU platforms – a process that requires thermo shocks and cycling, vibration tests and more.

“Service replacement parts should be available for a minimum of 10 years, where the military requires that parts be available for several decades,” he added. “The discontinuance of the PLC-4-Trucks P485 chip may impact the ability to provide service replacement parts in the future and the ability for new products to be backward compatible with legacy equipment.”

US$52 billion semiconductor plan

MEMA senior vice-president – government affairs Ann Wilson said during a Heavy Duty Aftermarket Week presentation that more pressure needs to be put on chip manufacturers to ensure vehicle manufacturers are served.

While US President Joe Biden has been cutting ribbons and touting the success of a US$52 billion semiconductor spending plan, “some of these chip manufacturers are coming to you and saying, ‘If you want some of these mature chips, you need to tell us right now and that’s it,'” she said.

The U.S. currently produces just 10% of the world’s supply of semiconductors, the White House said, when announcing the Chips and Science Act.

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John G. Smith is the editorial director of Newcom Media's trucking and supply chain publications -- including Today's Trucking,, TruckTech, Transport Routier, and Road Today. The award-winning journalist has covered the trucking industry since 1995.

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