P2135: Throttle Position Sensor/Switch A/B Voltage Correlation

What Is Code P2135?

The P2135 fault code is defined as “Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation.”

The Power Control Module (PCM) or Engine Control Module (ECM) logs this code when it detects a mismatch between the voltage signals from the Throttle Position Sensors (TPS) and the Accelerator Pedal Position Sensor (APPS). 

What does this mean?

Modern vehicles use a drive-by-wire system, meaning the throttle is electronically controlled rather than mechanically linked to the gas pedal. This system adjusts the throttle valve based on voltage readings from the following sensors:

• Throttle position sensors: These are mounted on the throttle body and monitor the position of the throttle plate (also called the throttle valve). They send voltage signals to the PCM to indicate how far the throttle plate is open.

• Accelerator pedal position sensors: These are located near the gas pedal. They measure how far you press the pedal and send corresponding voltage signals to the Power Control Module. 

NOTE: Modern cars generally have two APPS sensors on the accelerator pedal and one or two TPS sensors on the throttle body for redundancy and safety.

The PCM then compares the voltage signal from these sensors to ensure they align. If one sensor set indicates half throttle and the other indicates full throttle, the PCM detects a mismatch, which could point to a poor connection or a faulty sensor. 

As a result, the PCM will turn on the check engine light and force the car into fail-safe mode, significantly reducing engine power.

When this underlying issue triggers fail-safe mode, you may notice reduced fuel efficiency and even occasional stalling.

5 Common Symptoms of Error Code P2135

Error code P2135 can lead to a range of noticeable issues. Here are some of the most obvious signs: 

1. Illuminated Check Engine Light

You’ll notice the check engine light on your dashboard when the PCM detects an issue.

While it’s often caused by an incorrect voltage signal from the TPS or APP sensor, the check engine light can come on for issues unrelated to the P2135 code, such as a dirty throttle body. 

The best way to determine what’s wrong is to use an OBD-II scan tool to check the trouble codes or have a trusted mechanic take a closer look.

2. Reduced Engine Power or Fail-Safe Mode 

When the PCM detects a mismatch in the voltage signal from the throttle position sensor and accelerator pedal position sensor, it’ll activate fail-safe mode (also known as limp mode) to protect the engine. 

This mode limits the vehicle’s power and speed, making normal acceleration and driving difficult. 

A poor connection in the sensor wiring as well as short or damaged wiring could trigger this mode.

3. Poor Acceleration 

Your vehicle might have trouble picking up speed, even when the gas pedal is fully depressed. This is because the PCM misinterprets the throttle position sensor signal. As a result, your vehicle won’t accelerate properly.

If left unchecked, the underlying issue can lead to further complications with the system’s voltage readings. 

4. Unresponsive or Erratic Throttle Response 

Sometimes, the throttle might not respond properly, causing issues with revving and making it hard to accelerate or maintain a steady speed. In some cases, your car can unexpectedly speed up or slow down, often due to broken electrical connections.

5. Stalling or Engine Hesitation 

Your engine might hesitate, sputter, or even stall, especially when you come to a stop or hit the accelerator. Without accurate signals from the TPS sensor and accelerator pedal position sensor, the PCM can’t adjust the air-fuel mixture or maintain proper engine performance. 

5 Causes of the P2135 Code

Some possible triggers for the DTC P2135 include:

1. A faulty throttle position sensor 
2. A malfunctioning APP sensor
3. Damaged wiring or loose connections linking the TPS, APPS, or PCM
4. Throttle body issues 
5. A faulty Powertrain or Engine Control Module

Is P2135 Code Serious and Can You Drive With It?

Driving with a P2135 code can create unsafe driving conditions and may even damage your vehicle. 

Here’s how: 

The mismatch in voltage output signals between the TPS sensor and the accelerator position sensor can result in abnormal conditions, like loss of power or erratic throttle behavior. This makes driving dangerous.

If ignored, it can strain other components, such as the throttle body, the transmission, and even the engine. Broken electrical connections or a low voltage input issue can also negatively affect your car’s performance. 

That’s why you should have a mechanic check out your vehicle at the first sign of trouble.

How Do You Diagnose the P2135 Code?

The TPS and APPS are sensitive vehicle components that are prone to damage. If you’re unfamiliar with the diagnostic procedure, it’s best to consult a mechanic. 

Here’s how a trained technician will diagnose the root causes of DTC P2135. 

1. Connect an OBD-II scan tool to the vehicle’s diagnostic port to confirm the P2135 code and check for additional trouble codes, including circuit low input errors.

2. Use a multimeter to measure the voltage output from the sensor while manually operating the throttle plate.

3. Inspect for a faulty throttle position sensor and faulty accelerator position sensor by looking for broken electrical connections or other signs of defects.

4. Examine the throttle body for carbon deposits, dirt, or physical damage, as these create abnormal conditions.

5. Test the PCM for faulty signal interpretation and outdated or corrupted software using diagnostic software.  

What are the Repairs and Costs for the P2135 Code?

Depending on the root cause of the fault code P2135, your mechanic may try any of the following fixes: 

• Replace throttle position sensor: $150 to $710 (part and labor) 
• Replace accelerator pedal position sensor: $100 to $800 (part and labor) 
• Change damaged wiring in the TPS circuit and APPS circuit: $50 to $150 
• Reprogram or replace the PCM: $300 to $1,000 (part cost) 

3 FAQs on DTC P2135

Here are answers to three common questions about the P2135 code: 

1. What Other Codes Can Appear with P2135?

Here are some engine codes related to P2135: 

• P0120 to P0124: These codes indicate issues with the throttle position sensor circuits, such as signal interruptions, unusual voltage signals, or performance problems.
   
• P0220 to P0224: These codes reference issues with the second throttle position sensor (Sensor B) and its circuit specifically.

• P2119: A common cause of this code is an issue with the throttle actuator control system, which is often linked to the throttle body or its sensors.

• P2138: This code indicates voltage inconsistencies between the two accelerator pedal position sensors or throttle position sensors, which is a common cause of throttle response issues.

2. Can You Fix the P2135 Code Yourself?

P2135 code repair is best left to a professional mechanic.

Here’s why:
The issue often involves complex components like the throttle position sensor, accelerator pedal position sensor, throttle body, as well as the vehicle’s wiring and control module. 

A DIY approach can sometimes create more problems. Certain fixes, such as reprogramming the PCM, also require specialized tools and software.

A professional mechanic can perform the job correctly and resolve the root cause of the issue, saving time, money, and potential headaches.

3. How Can You Prevent the P2135 Code from Reoccurring?

Preventing the code P2135 involves regular maintenance and proactive care of your vehicle’s throttle and sensor systems. 

Here are some practical tips: 

• Follow your vehicle’s maintenance schedule.
• Inspect the TPS, APPS, and PCM wiring and connectors regularly.
• Ensure the sensors are properly calibrated after repair. 
• Use quality replacement parts.
• Keep the vehicle software updated.