The National Highway Traffic Safety Administration is looking into problems that could affect more than 1.37 million vehicles made by Honda, Toyota and Ford. NHTSA probes could lead to recalls; two of the inquiries have been ongoing since last October.

NHTSA runs several dozen defect investigations at any given time, all stemming from public complaints and petitions. A recall can be issued if the agency deems there is sufficient evidence of a widespread problem, although this does not always happen.

The agency updated its investigation reports regarding the three automakers, Honda, Toyota and Ford.

About 724,982 Ford Escape and Fusion models from the 2009 to 2011 model years are under investigation for failing electronic throttle bodies that could cause the vehicles to stall or surge unexpectedly. The sister Mercury Mariner and Milan models are also included. The investigation follows an October petition that urged NHTSA to investigate 1.6 million Escape SUVs from the 2005 to 2012 model years for the same alleged problem.

In total, NHTSA and Ford have found 1,448 instances relating to the throttle body, which controls vehicle acceleration. Faults with the throttle body caused many of the vehicles to resort to a “limp home” mode, which restricts vehicle speed and engine revs to protect failed components from damaging the powertrain.

The various “limp home” modes can cause the vehicle to surge or appear to stall, even though the engine is still running, the report said. Ford said it had 27,505 warranty claims relating to repair or replacement of the throttle bodies.

The agency has also received requests to investigate the 2001-2004 Escape and the 2000-2003 Ford Taurus and Mercury Sable models for alleged stuck throttles, although no action has been taken.

The 2004-2009 Toyota Prius is being investigated for excess wear on a coupling joint of the steering shaft. About 561,000 vehicles may be affected, although the investigation is based on one complaint and the defect may have been resolved through an earlier recall.

In November, Toyota recalled 670,000 second-generation Prius models from 2004-2009 that had intermediate extension shafts that were of “insufficient strength” and could snap. The shafts connect the steering wheel near its gear box inside the cabin. Toyota said that the shaft could break if drivers turn the steering wheel to its full left or right positions at low speeds, such as when parking, or if a tire were to hit a curb at low speeds.

In June 2011, Toyota recalled 52,000 models of the first-generation Prius to fix a power steering problem that could make the car difficult to turn.

NHTSA engineers are looking into the 2005 Honda Pilot for unexpected emergency braking and stability control intervention on as many as 87,803 vehicles. The agency has recorded 185 instances of Pilots applying the brake assist function, which automatically applies full braking force when the pedal sensors detect a panic stop, without reason.

Some owners alleged that the car applied the brakes without the pedal being pressed. Twenty complaints allege the Pilot’s stability control system intervened without reason, which caused the vehicle steering to pull by application of individual brakes.

Honda has identified problems with the yaw sensors and algorithms used to determine if the vehicle is in a slide or other emergency situation.