Closed Throttle Position Switch Malfunction
The PCM has detected an inconsistency in the closed throttle position of the throttle plate.
Code Set Parameters
Typically this code occurs on vehicles which are equipped with “drive by wire” throttle body systems that do not use an accelerator cable. If the throttle plate is opened manually (for cleaning, etc.) with the ignition switch in the on position, this code will be set and the service engine illuminated. If the actual throttle position varies from the desired throttle position for a specified amount of time (usually 5-seconds) a code will be stored and a malfunction indicator lamp will be illuminated.
Engine stall at idle, engine stall when releasing the accelerator pedal at cruising speeds, low engine idle RPM, high engine idle RPM, a stored trouble code, and an illuminated service engine soon lamp are all listed among the possible symptoms associated with this powertrain code. Some models will also enter “limp-in” mode that will severely limit the maximum RPM level and make driving the vehicle nearly impossible.
Most vehicles that present this code can only be repaired by replacing the entire throttle body assembly. This code is usually associated with “drive by wire” throttle bodies that are controlled by the PCM but can also refer to conventional throttle bodies as well. Other causes include a faulty throttle position sensor, bad closed throttle position switch or wide open throttle position switch, faulty electrical connector or wiring, or a faulty PCM. PCM failure is rare.
Before diagnosing this code, make sure that no other related codes are present. If other throttle position sensor related codes are present, diagnose and repair these codes first before attempting to diagnose this code. Technicians report that throttle position sensors are often replaced in error when closed throttle position switches are at fault. A thorough diagnosis is necessary prior to condemning any component.
- In many vehicles, the PCM utilizes input data from the throttle position sensor, closed throttle position switch, and wide open throttle position switch, to calculate several output actions
- Some vehicle drivability systems are only equipped with a throttle position sensor that performs the duties of both the closed throttle position switch and wide open throttle position switch, as well as other throttle position monitoring duties
The throttle position sensor is typically a rheostat type sensor that is mounted on the throttle body assembly, directly opposite of the accelerator linkage
- As the throttle is opened, the throttle plate shaft (which is normally inserted into the throttle position sensor) moves the sensor contact points, changing circuit resistance levels and varying the voltage signal sent to the PCM
- These voltage degrees are interpreted by the PCM as percentages that the throttle plate is opened
- As the actual throttle position changes, voltage input to the PCM should change smoothly
- Throttle position usually ranges from less than 5-percent (at idle) to 100-percent (at wide open throttle).
Technicians report that this code is most often exhibited in vehicles that are equipped with a drive by wire accelerator system
- This type of system uses no accelerator cable but relies on an electric motor and a voltage signal from the PCM to open and close the throttle
- Many of these types of throttle bodies are not serviceable
- The throttle position sensor, actuator motor, closed throttle position switch, and/or wide open throttle position switch are integrated into the throttle body and cannot be purchased or replaced separately.
Several tools will be instrumental in successfully diagnosing this code
- A suitable OBD-II scanner (or code reader) and a digital volt/ohmmeter will be most helpful in performing a successful diagnosis
Begin with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- Continue by clearing the code and operating the vehicle to see if it returns
- This will help to determine whether or not the malfunction is intermittent
After the codes are cleared, test drive the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made
If the code returns, inspect system wiring and connectors for signs of damage or corrosion
- If no visible signs are detected, test resistance at the throttle position sensor, closed throttle position sensor, and/or wide open throttle position sensor and compare your findings with manufacturer’s specifications
- If actual readings fail to coincide with manufacturer’s specifications, replace the sensor/s as needed
- Remember that certain throttle bodies are not equipped with serviceable sensors and the entire unit will need to be replaced
- This is more common in drive by wire systems
- Connect the 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 voltage drops or glitches are detected, replace the sensor in question, reset the code, and retest the system
If all sensors check out, disconnect the PCM and sensor connectors and test continuity in the power, ground, and signal circuits
- Compare your findings with manufacturer’s specifications and repair open or shorted wiring as necessary
- If all wiring and sensors check out, suspect PCM failure (although this is very rare)