P2109 – Throttle/Pedal Position Sensor A Minimum Stop Performance

What is Code P2109?

P2109 is a generic OBD-II diagnostic trouble code (DTC) that stands for "Throttle/Pedal Position Sensor 'A' Minimum Stop Performance". It indicates that the powertrain control module (PCM) has detected a fault with the throttle position sensor (TPS) or accelerator pedal position sensor (APPS) minimum stop performance.

How Urgent is P2109? Can You Keep Driving?

A P2109 code should be considered severe and addressed immediately. When this code is triggered, the vehicle will likely go into "limp home mode" with reduced engine performance. Acceleration may be limited or disabled entirely. It is not safe to continue driving with a P2109 code present. Have the vehicle towed to a repair shop or dealership for diagnosis.

Technical Details of P2109

The throttle position sensor (TPS) and accelerator pedal position sensor (APPS) are key components of the electronic throttle control (ETC) system, also known as drive-by-wire. These sensors monitor the position of the throttle plate and accelerator pedal, respectively.

The PCM uses these sensor inputs to control the throttle actuator motor, which opens and closes the throttle plate to regulate air intake. Code P2109 sets when the PCM detects that the "A" sensor's reading at closed throttle/minimum stop position is out of the acceptable range, either too high or too low.

Specifically, the PCM monitors the minimum TPS voltage when the closed throttle position learning is completed. If the TPS voltage is less than 0.20 V or more than 0.95 V (exact values vary by make and model), a P2109 code will be stored and the check engine light illuminated.

Is P2109 a Manufacturer Specific Code?

Code P2109 is a generic powertrain code that applies to OBD-II equipped vehicles from various makes, including but not limited to Toyota, Ford, Chrysler, GM, Nissan, Mazda, Hyundai, Kia, and Subaru. The code has the same general meaning for all vehicles, but the exact troubleshooting steps and repair procedures may vary slightly between makes and models.

Parts Involved

The main components related to code P2109 are:

• Throttle Position Sensor (TPS) – Measures the opening angle of the throttle plate
• Accelerator Pedal Position Sensor (APPS) – Measures the position of the accelerator pedal
• Throttle Actuator Motor – Opens and closes the throttle plate based on signals from the PCM
• Throttle Body Assembly – Housing containing the throttle plate, TPS, and actuator motor
• Powertrain Control Module (PCM) – The vehicle's main computer that monitors sensors and controls actuators

Common Causes of P2109

Potential causes of a P2109 code include:

1. Faulty throttle position sensor
2. Damaged or corroded TPS wiring or connectors
3. Faulty accelerator pedal position sensor
4. Damaged or corroded APPS wiring or connectors
5. Throttle body mechanical issues (carbon buildup, sticking throttle plate)
6. Faulty throttle actuator motor
7. PCM software issues or failure

Diagnosing P2109 Step-by-Step

1. Connect an OBD-II scanner and retrieve all stored trouble codes and freeze frame data.
2. Clear the codes and test drive the vehicle to see if code P2109 returns.
3. Perform a visual inspection of the throttle body, sensors, wiring, and connectors. Look for damaged, loose, or corroded connections.
4. Use a multimeter to test the TPS and APPS for proper reference voltage (usually 5V), ground, and signal output. Compare readings to manufacturer specifications.
5. Monitor the TPS and APPS voltage signals with a scan tool or oscilloscope while slowly depressing the accelerator pedal. The voltage should change smoothly without dropouts or spikes.
6. If the sensors test okay, check for throttle body mechanical issues like carbon buildup or a sticking throttle plate.
7. Test the throttle actuator motor operation and wiring.
8. If all components test okay, suspect a faulty PCM or software issue.

Repair Solutions for P2109

Depending on the root cause determined from diagnosis, possible repairs for a P2109 code include:

• Replacing the throttle position sensor
• Repairing damaged TPS or APPS wiring and connectors
• Replacing the accelerator pedal position sensor
• Cleaning the throttle body and throttle plate
• Replacing the throttle body assembly
• Replacing the throttle actuator motor
• Reprogramming or replacing the PCM

Preventing P2109

To help prevent a P2109 code from occurring, follow these tips:

• Perform regular throttle body cleaning service every 50,000-100,000 km (30,000-60,000 miles)
• Address any related trouble codes promptly
• Avoid aftermarket "performance chips" or PCM tuning that can alter throttle control
• Maintain the battery and charging system to prevent voltage issues that can damage sensors

Cost of Diagnosis and Repair

Diagnosing a P2109 code can cost anywhere from $75-$150 USD (€70-€135 EUR) for an hour or two of labor.

The cost of repairs will depend on the specific issue found:

• Throttle position sensor: $100-$300 USD (€90-€270 EUR)
• Accelerator pedal position sensor: $150-$500 USD (€135-€450 EUR)
• Throttle body assembly: $300-$750 USD (€270-€675 EUR)
• Throttle actuator motor: $200-$600 USD (€180-€540 EUR)
• PCM replacement: $500-$1500 USD (€450-€1350 EUR)

Related Codes

Other throttle and accelerator pedal related codes that may appear alongside P2109 include:

• P0121-P0124 – Throttle Position Sensor Codes
• P0220-P0229 – Accelerator Pedal Position Sensor Codes
• P2110-P2112 – Throttle Actuator Control Codes
• P2135 – Throttle Position Sensor/Switch A/B Voltage Correlation

By understanding code P2109, its causes, symptoms, and repairs, technicians can accurately diagnose and fix electronic throttle control issues. Proper maintenance and prompt repairs can prevent costly damage and keep vehicles running smoothly.

Frequently Asked Questions about P2109

What does the OBD-II code P2109 mean?

P2109 is a generic diagnostic trouble code (DTC) that stands for “Throttle/Pedal Position Sensor ‘A’ Minimum Stop Performance”. It indicates that the powertrain control module (PCM) has detected a fault with the throttle position sensor (TPS) or accelerator pedal position sensor (APPS) minimum stop performance.

Is it safe to drive with a P2109 code?

No, it is not safe to continue driving with a P2109 code present. When this code is triggered, the vehicle will likely go into “limp home mode” with reduced engine performance. Acceleration may be limited or disabled entirely. Have the vehicle towed to a repair shop or dealership for diagnosis.

What are the common symptoms of a P2109 code?

Common symptoms of a P2109 code include:

• Lack of throttle response
• Limited or no acceleration
• Engine stalling when idling
• Hesitation when accelerating
• Cruise control not working

What causes a P2109 code?

Potential causes of a P2109 code include:

• Faulty throttle position sensor (TPS)
• Faulty accelerator pedal position sensor (APPS)
• Damaged wiring or connectors for the TPS or APPS
• Issues with the throttle body like carbon buildup or sticking
• Faulty throttle actuator motor
• PCM software issues

How do you diagnose a P2109 code?

To diagnose a P2109 code:

1. Scan for all trouble codes and note freeze frame data.
2. Visually inspect the throttle body, sensors, wiring, and connectors.
3. Test the TPS and APPS voltages with a multimeter or oscilloscope.
4. Check for throttle body mechanical issues.
5. Test the throttle actuator motor and wiring.
6. Check the PCM for software updates or internal faults.

Can a bad throttle position sensor cause a P2109?

Yes, a faulty throttle position sensor is one of the most common causes of a P2109 code. The TPS monitors the throttle plate angle and sends a voltage signal to the PCM. If this signal is out of range at the closed throttle position, a P2109 may be triggered.

Can a dirty throttle body cause a P2109?

Yes, a dirty throttle body with carbon buildup can cause the throttle plate to stick and not fully close. This can lead to an incorrect TPS reading at the minimum stop position and set a P2109 code. Cleaning the throttle body may resolve the issue.

How much does it cost to fix a P2109 code?

The cost to repair a P2109 code varies depending on the root cause. Throttle position sensors cost around $100-$300 to replace, while a throttle body assembly runs $300-$750. Expect to pay $75-$150 in diagnostic labor to have the code properly diagnosed first.

Can I diagnose a P2109 code myself?

Diagnosing a P2109 code requires advanced knowledge and specialized tools like a scan tool, digital multimeter, and oscilloscope. It’s best left to a professional technician unless you have the proper equipment and experience. Misdiagnosis can lead to unnecessary parts replacement.

What happens if you don’t fix a P2109 code?

Ignoring a P2109 code can leave your vehicle in a reduced power failsafe mode. You may experience poor acceleration, rough idle, stalling, and poor fuel economy. In some cases, the vehicle may not accelerate at all, leaving you stranded.

Can low battery voltage cause a P2109 code?

Indirectly, yes. While low battery voltage doesn’t directly set a P2109, it can cause issues with the throttle actuator motor and PCM memory that can lead to a P2109. Always check and maintain proper battery voltage, especially if the code occurs after a dead battery.

Can a P2109 code clear itself?

In most cases, a P2109 code will not clear on its own and will require diagnosis and repair to address the underlying problem. However, if the code was set by a temporary factor like a loose connector that fixes itself, the code may clear after multiple drive cycles without reoccurring.

Is a P2109 code serious?

Yes, a P2109 code should be considered serious as it can put the vehicle into limp mode and severely limit drivability. You should not continue driving with this code present and should have it diagnosed as soon as possible to avoid being stranded.

What is the difference between a TPS and APPS?

The throttle position sensor (TPS) measures the actual position of the throttle plate inside the throttle body. The accelerator pedal position sensor (APPS) measures the position of the gas pedal pushed by the driver. Both send signals to the PCM to control the throttle motor.

Can a P2109 code damage my engine?

The P2109 code itself does not cause engine damage. However, the underlying problem that triggered the code, such as a faulty throttle body or sensor, may lead to poor air-fuel ratios and misfires which can damage the engine over time if left unrepaired.

What does “minimum stop performance” mean for P2109?

“Minimum stop performance” refers to the throttle position sensor (TPS) reading when the throttle plate is fully closed at idle. If this TPS voltage is not within the expected range, often 0.20V-0.95V, a P2109 code may be set.

Can a P2109 code affect transmission shifting?

Yes, a P2109 code can affect transmission shifting, especially in vehicles with drive-by-wire throttle systems. The faulty TPS signal can cause incorrect throttle position data to be sent to the transmission control module (TCM), resulting in harsh, delayed, or early shifts.

What does “throttle/pedal position sensor A” refer to?

“Throttle/pedal position sensor A” refers to the primary or main sensor that measures throttle plate or accelerator pedal position. Some vehicles use multiple sensors for redundancy, labeled A, B, C, etc. Code P2109 applies specifically to a fault with the primary “A” sensor.

Can a vacuum leak cause a P2109 code?

No, a vacuum leak will not directly cause a P2109 code as this relates to the throttle position sensor performance. However, a large vacuum leak may cause idle issues that could be misinterpreted as a throttle problem and should be ruled out during diagnosis.

What other codes may be present with a P2109?

Other common codes that may appear alongside a P2109 include:

• P0121-P0124 – Throttle Position Sensor Codes
• P0220-P0229 – Accelerator Pedal Position Sensor Codes
• P2135 – TPS/APPS Correlation
• P2110-P2112 – Throttle Actuator Codes

The key to accurately diagnosing a P2109 code is understanding the relationships between the throttle position sensor, accelerator pedal position sensor, throttle actuator, and PCM. Careful testing of each component is necessary to determine the root cause and prevent misdiagnosis.