WASHINGTON — The nation’s top auto safety regulator has upgraded its investigation of high-pressure fuel pump failures in certain heavy-duty Ram diesel trucks.
According to a document made public Tuesday, NHTSA’s Office of Defects Investigation is expanding its safety probe to include the Tier 1 supplier Robert Bosch, which makes the high-pressure fuel pumps. The expanded probe also includes any automakers who installed the part and are experiencing similar failures.
In October 2021, NHTSA launched its investigation of high-pressure fuel pump failures in 2019-20 Ram 2500, 3500, 4500 and 5500 heavy-duty trucks equipped with 6.7-liter Cummins turbodiesel engines after reports alleging incidents of stalling or loss of power. The upgraded probe also covers 2014-22 Ram 1500 trucks.
In addition to those vehicles, the probe covers Bosch’s C4 fuel pumps, and 2021-22 Jeep Gladiator, 2014-20 Jeep Grand Cherokee and 2020-22 Jeep Wrangler vehicles. It also covers older models from BMW, including 2014-18 BMW 328D, 2014-16 BMW 535D and 2015-17 BMW X3 vehicles.
About 490,000 vehicles could be affected.
The upgraded probe — now an engineering analysis — is a required step before NHTSA can seek a recall.
NHTSA said an information request letter from BMW “indicated that failed pumps on their vehicles were caused by an interaction between pump internal components and U.S. market diesel fuel, leading to increased slip and eventual particle-generating wear surface.”
The agency now will investigate whether a similar root cause is associated with vehicles previously recalled by Stellantis and if similar wear dynamics occur on pumps supplied to other automakers.
Stellantis spokesperson Eric Mayne said the automaker is continuing to lend its full cooperation to the agency.
Bosch said it was aware of the investigation and “will respond accordingly.”
BMW did not immediately respond to requests for comment.
