P0510

P0510 is a legacy code from the cable-throttle era indicating the closed throttle position switch (a discrete on/off switch separate from the TPS potentiometer) is not transitioning from closed to open as the throttle plate moves off idle, or vice versa. On modern drive-by-wire vehicles this code is essentially obsolete and you will only see it on pre-2005 applications that still used a mechanical idle switch in parallel with the analog TPS. Cheapest-first: back-probe the idle switch signal wire with a meter and verify it pulls to ground when the throttle is fully closed and opens (5V or floating) the instant the pedal is touched, then if the switch is mechanical and adjustable, loosen the mounting screws and rotate to spec. If the switch is integral to the TPS assembly, the entire TPS gets replaced as a unit. Caveat: on vehicles where this is a separate switch, a sticky throttle cable or a misadjusted idle stop screw will hold the throttle plate slightly open at hot idle and set this code without any switch fault at all.

Vehicle-specific patterns: 1996-2002 Toyota 4Runner, Tacoma, and T100 with the 3.4L 5VZ-FE use a separate idle switch on the throttle body that corrodes internally. 1995-2001 Nissan Pathfinder, Maxima, and Frontier have the closed throttle switch built into the TPS and the whole sensor is replaced when it sticks. 1996-2000 Honda Accord and Civic with the secondary idle-air-control-adjacent closed-throttle switch fail from carbon buildup holding the throttle plate cracked open. 1997-2003 Subaru Legacy and Forester see TPS-integrated idle switches fail from contact wear. Estimated repair: $70 to $240.