P2166 OBD-II Trouble Code: Throttle/Pedal Position Sensor D Maximum Stop Performance

diagnostic check engine light

P2166 code definition

The P2166 trouble code detects an electrical issue with the throttle pedal position sensor circuit.

What the P2166 code means

The P2166 code is a standard OBD-II trouble code that notes an error with the throttle pedal position sensor circuit. The throttle position sensor notes the position of the throttle pedal, so that the throttle actuator can assure that engine acceleration is as desired. The throttle pedal position sensor sends data to the powertrain control module (PCM), as well as to many other control modules, such as the fuel injection control module, transmission control module, and turbo control module. When one of the control modules detects an error from the throttle pedal position sensor circuit, or from the throttle actuator control motor circuit, then the P2166 trouble code will be triggered.

What causes the P2166 code?

Potential causes of the P2166 trouble code are:

  • Defective throttle position sensor
  • Faulty throttle position actuator
  • Malfunctioning throttle actuator control motor
  • Damaged or defective electrical components in the system, often in the throttle actuator motor
  • Damaged ground wire
  • Loose control module ground strap
  • Faulty PCM

What are the symptoms of the P2166 code?

The P2166 trouble code will often be accompanied by an illuminated check engine soon Warning Light on the vehicle’s gauge cluster. Severe engine and transmission problems are common as well, such as hesitant acceleration, inability to accelerate, constant stalling and misfiring, and often an inability to start at all. The vehicle may also experience black smoke from the exhaust system during startup, as well as reduced fuel efficiency.

How does a mechanic diagnose the P2166 code?

The P2166 code will be diagnosed using an OBD-II trouble code scanner. A certified mechanic will use the scanner to view the freeze frame data to help assess the P2166 code. The scanner will also be used to check for additional trouble codes, as detected codes should always be addressed in the order in which they appear. The mechanic should then reset the trouble codes, restart the vehicle, and check to see if the code remains detected. If not, then it was likely triggered erroneously, or represents an intermittent error.

If the P2166 code remains detected following the reset, then the technician will visually inspect the electrical components in the throttle actuator and throttle position systems, as well as in the controller area network (CAN). Any fuses that are blown, connectors that are corroded, or wires that are shorted will require replacement. Ground wires and straps will require inspection as well. The voltage and ground signals should then be tested for the throttle position sensor and the throttle actuator control motor, to make sure they fall within the manufacturer’s specifications. If the problem is still unresolved, then thorough inspection of the control modules is in order.

After the replacement of any components, the mechanic will halt the inspection to once more reset the trouble codes, restart the vehicle, and check to see if the code remains. By doing this, the technician will know as soon as the issue is resolved.

Common mistakes when diagnosing the P2166 code

The most frequently made error when diagnosing the P2166 code comes from a failure to comply with the OBD-II trouble code diagnosis protocol. This protocol should always be follow precisely, to help ensure that inspections and repairs are accurate and efficient.

Since the P2166 code is often accompanied by other trouble codes, it is common for additional codes to be addressed independently, when they represent a reaction to the P2166 code. Codes should be addressed in the order in which they appear to make sure that the root of the problem is fixed before the resulting issues are. Often fixing the P2166 code will resolve other present codes.

How serious is the P2166 code?

A vehicle with the P2166 trouble code may or may not be drivable. Even if the car is drivable, there will likely be drivability issues, and continuing to operate the vehicle can cause severe damage to the transmission. An inspection should be scheduled as soon as the P2166 code is detected.

What repairs can fix the P2166 code?

Repairs for the P2166 trouble code include:

Additional comments for consideration regarding the P2166 code

The P2166 trouble code is only in cars that utilize an electronically controlled throttle body.

Need help with a P2166 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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