Error Code P0510 is defined as Closed Throttle Position Switch Malfunction. This means there’s an inconsistency in the closed throttle position of the throttle plate.

This error code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system, or vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs vary form one vehicle make and/or model to another.


For certain vehicles, throttle body or linkage may contain a switch that signals the PCM (powertrain control module, also known as ECM or engine control module in other vehicles makes) that the throttle body is in closed position. When throttle body is shut close, the switch will be in closed position. PCM uses the switch to keep engine in conjunction with the idle air control valve when at idle mode, or even go into fuel cut mode when coasting.

Some vehicles may also have WOT (wide open throttle) switch. If either the closed throttle switch or WOT are not engaged, then the PCM will assume the throttle is partly open, affecting the vehicle’s air/fuel ratio.

Error Code P0510 usually appears when vehicles with “drive by wire” throttle body systems that don’t use accelerator cable. If the throttle plate is manually opened (for cleaning, etc.,) with ignition switch in the on position, the code will be set and trigger the Check Engine light. If the actual throttle position varies from the desired throttle position for a specified amount of time (about 5 seconds), the code will also be stored and the Check Engine light will also light up.

In cases where more than one trouble code is set, such as P0120 (TPS/Pedal Position Sensor A circuit Malfunction) – that may indicate an open in the ground or bad connection at the TPS (throttle position sensor).

Common Symptoms

In many cases, Error Code P0510 will not show many symptoms, aside from the Check Engine light and the registered code. For some cases however, symptoms can include:

  • Engine stalls at idle
  • Low engine idle RPM
  • High engine idle RPM
  • Engine stalls when releasing accelerator pedal at cruising speed

Other models may also experience “limp-in” mode which will limit the maximum RPM level, making the vehicle very difficult, if not impossible to drive.

Possible Causes

There are many possible causes for this code, and in many vehicles, the code can only be fixed by replacing the whole throttle body assembly. Also, this code is usually associated with “drive by wire” throttle bodies, which are controlled by the PCM, but can also refer to a conventional throttle body as well. Other common causes of this error code include:

  • Faulty TPS
  • Faulty electrical wiring or connectors
  • Bad closed throttle position switch
  • Wide open throttle position switch
  • Open circuit or loose wiring harness, or dirty connection
  • Tampered throttle body idle set screw
  • Failed PCM (rare)

How to Check

Start the diagnosis by visually inspecting all wiring and connectors. Consequently, any damages to these wirings must be repaired or replaced. Make sure to retest the system after repairs.

If all system wirings are in good shape, connect the scanner to diagnose and record the stored code and freeze frame data. This information can be used to determine whether the problem is an intermittent condition or not. Then clear the codes and take the vehicle for a test drive. If the code returns, that means the problem is intermittent. For intermittent condition, check all wirings and connectors to the system and look for signs of damage or corrosion.

If there are no visible signs of damage, then test the resistance of the TPS, closed throttle position sensor, and/or open throttle position sensor, and compare your findings with the specifications provided by the vehicle’s manufacturer.

Note that some throttle bodies don’t come with serviceable sensors, which means the whole unit must be replaced – a common case in drive by wire systems.

Connect the DVOM (digital volt-ohmmeter) to the sensor signal wire and ground and observe the voltage sweep as the throttle plate is slowly opened and closed. If the voltage glitches or drops, replace the faulty sensor. Reset the codes and then retest again.

If the sensors are in good shape, disconnect the PCM and sensor connectors and test for continuity in ground, power and signal circuits. Compare your findings from the specifications provided by the manufacturer. Repair any open or shorted wiring.

If all wirings and connectors are in good shape, then the problem can be a case of a failed PCM (although this is very rare).

How to Fix

There are many ways to fix this error code, which of course, depends from the diagnosis.

To fix for the wiring harness problem

Disconnect wiring harness connector at the TPS or closed throttle position switch and the harness connector at the PCM. Then, use the DVOM (digital volt-ohmmeter), set it to ohms scale and then connect each end to the same wiring, use a wiring diagram for reference and test for continuity between the PCM and the switch. The resistance should be present in the wiring between the switch and the PCM. If you see an infinite reading, that means there’s an open circuit problem. If this is the case, then repair open in wiring or replace the wire in the harness assembly.

To fix for closed throttle position switch problem

Disconnect wiring harness connector at closed throttle position switch or TPS and then use the DVOM to test for continuity of the leads on the two pins at the closed throttle position switch or sensor, your options totally depends on the vehicle. There should be resistance in the throttle body in closed position. If the throttle body is not touching or fully closing switch, it means there may have been an adjustment done to the idle set screw. Simply re-adjust the set screw based on the manufacturer’s specifications.

Other repairs include:

  • Repair or replace damaged, corroded, shorted or disconnected wirings, connectors and other components as necessary

Before you start diagnosing for this code, make sure there no other related codes present. If there are other related codes, then diagnose and repair those codes first before you proceed on diagnosing this error code. In many cases, people replace a perfectly fine throttle position sensor, when the problem is the closed throttle position switch.