P2135: TP Sensor/Switch A/B Voltage Correlation

What is P2135?

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

The Powertrain Control Module (PCM) or Engine Control Module (ECM) logs this trouble code when there’s a mismatch in the voltage from the throttle position sensor and the accelerator pedal position sensor.

So what does that mean? 

The throttle position sensors (A and B) are mounted on the throttle body inlet. These sensors send a voltage signal to the Powertrain Control Module, indicating the position of the throttle plate (also known as the throttle valve.)

The Powertrain Control Module interprets the voltage signal, determining how far the throttle plate is open.

The accelerator position sensor (located near the gas pedal) detects how far you push the pedal and sends a signal voltage to the PCM. The more you depress the gas pedal, the higher the voltage signal.

The PCM uses the voltage reading from these sensors and compares it with its programmed parameters.

If the voltage reading from the throttle position sensors indicates one’s at half throttle and the other at full, the PCM will turn the Check Engine Light on and log the code P2135.

Note: Around the 1990s, the automotive industry switched to drive-by-wire electronic throttle control technology, offering greater control over NOx emissions, fuel economy, cruise control, etc. Prior to that, the throttle was controlled mechanically.

Common symptoms

Several notable symptoms often go with DTC P2135. Here are the most obvious signs of a problem with the throttle position sensor (TPS sensor, TP sensor) and the accelerator pedal position sensor (APP sensor): 

1. Illuminated Check Engine Light 

You’ll notice the Check Engine Light on your dashboard when the Powertrain Control Module detects an issue it can’t correct.

While this could mean an erroneous voltage signal from the TPS sensor or the accelerator pedal position sensor, it could also be due to several other operational issues.

So, it’s best to use an OBD-II scan tool to determine the exact cause of the Check Engine Light on your dashboard or have your vehicle diagnosed by a reputable mechanic.

2. The Vehicle Stutters On Acceleration

If you’ve noticed your vehicle stuttering seconds after you’ve stepped on the accelerator pedal, it could be a sign of the fault code P2135.

It’s best to have your car diagnosed ASAP, as this issue occurs when the accelerator pedal position sensor cannot detect the exact position of the gas pedal.

3. Acceleration Problems 

Poor acceleration is another common sign of the fault code P2135.

Here, the PCM fails to determine the accelerator pedal position and cannot send proper commands to open the throttle plate. As a result, your vehicle won’t speed up as fast as it should.

4. Vehicle Goes Into Limp Mode

When the PCM logs fault code P2135, it may put your vehicle into limp mode — a safety feature that protects you and your vehicle.

Here the PCM limits the throttle opening to 5-15%, reducing your vehicle’s revolution per minute (RPM) and speed. You may also find the air conditioning not working, or your vehicle may be stuck in 2nd or 3rd gear. 

5. Complete Loss Of Engine Power

Sometimes, the fault code P2135 may cause a complete loss of engine power.

Usually, this happens when the accelerator pedal sensor fails, forcing you to pull over. So, it’s best to fix the fault code P2135 soon.

Can I still drive?

A throttle control system error can pose many drivability problems, leading to dangerous circumstances in heavy traffic, around turns, or while cruising at top speeds.

So, if you’ve noticed any signs of the code P2135, it’s advisable to have the DTC P2135 addressed as soon as possible. Doing so may help mitigate secondary issues and additional repair costs. 

P2135 causes

The possible triggers for the fault code P2135 include:

• A faulty throttle position sensor 
• A malfunctioning APP sensor 
• Open, corroded, or shorted TP Sensor connector or accelerator position sensor connector, or harness
• Broken electrical connections or wiring damage in the throttle position sensor circuit or the accelerator position sensor circuit 
• Damaged or distorted throttle body top cover or throttle valve
• A faulty throttle body assembly
• Incorrect dielectric grease 
• A faulty Powertrain or Engine Control Module

Diagnosis

The TP sensor and accelerator pedal sensor systems are sensitive and prone to damage. So, if you’re unfamiliar with the diagnostic procedure, it’s best to consult a certified ASE technician.

Here’s how a skilled technician would diagnose the engine code P2135:

1. Turn the ignition switch off and begin the diagnosis using a scan tool to check for the P2135 (or any other code) stored in your vehicle’s PCM.
2. Then, clear the Check Engine Light and inspect the freeze frame data to pinpoint the issue. 
3. Next, check the manufacturer’s Technical Service Bulletins (TSBs) for recommended solutions. 
4. Then, check the throttle body position sensor and accelerator pedal position sensor terminals for short damaged wiring or damaged components.  
5. If the Check Engine Light is still on, check the factory service manuals to conduct a signal voltage test of the throttle body position sensor and the accelerator pedal position sensor.
6. Here, the main throttle body position sensor output voltage should be 0.9V or less, and the sub-TP sensor output voltage should be between 0.2V and 4.8V. The accelerator pedal position sensor should start at a low voltage and increase as you depress the pedal.

Note: The throttle position and accelerator position sensors shouldn’t be unplugged when checking them for broken electrical connections. Once unplugged, you’ll need a scan tool to perform an initialization of the throttle position sensor and accelerator pedal position sensor. 

Possible repairs for P2135 & Costs

Depending on the exact cause of the fault code P2135, your mechanic may refer to the factory service manuals and apply any one or more of the following fixes: 

• Install a new throttle position sensor (make sure to clean the throttle body using a throttle body cleaner)
• Replace faulty accelerator pedal position sensor
• Fix or replace an open, short damaged wiring in the throttle position sensor circuit 
• Repair or replace a poor electrical connection or corroded wiring in the accelerator pedal position sensor circuit
• Conduct a PCM reflash or update

The repair costs for the engine code P2135 may vary from $100 to $1000 depending on the number of damaged components, make, and model of your vehicle.

For example, a GMC Sierra 1500 throttle body replacement costs roughly $350, including labor and parts. But, a 2010 Audi A4 Quattro throttle body replacement costs roughly $780 to $950. 

Here are the average estimated costs:

• Accelerator pedal position sensor: $150 to 250
• Throttle body position sensor: $150 to $250
• Throttle body actuator: $500 to $750
• Wiring repair or replacement: $100 to $1000

2 DTC P2135 FAQs

Let’s look at some frequently asked questions and answers about the trouble code P2135:

1. What Are The Other Fault Codes Related To DTC P2135?

Here are the related engine codes to DTC P2135:

• P0120: Throttle Position Sensor A / Accelerator Pedal Position Sensor / Switch A Circuit Malfunction
• P0122: Throttle Position Sensor A / Accelerator Pedal Position Sensor / Switch A Low Input
• P0123: Throttle Position Sensor A / Accelerator Pedal Position Sensor / Switch A High Input
• P0220: Throttle Position Sensor B / Accelerator Pedal Position Sensor / Switch B Circuit Malfunction
• P0222: Throttle Position Sensor B / Accelerator Pedal Position Sensor / Switch B Low Input
• P0223: Throttle Position Sensor B / Accelerator Pedal Position Sensor / Switch B High Input

2. Is the Fault Code P2135 Labeled Differently In Different Vehicles?

Yes, different vehicle manufacturers may label the fault code P2135 differently.

For example, the Nissan Infiniti labels this fault code as “Throttle Position Sensor Circuit Range/Performance.” On a Hyundai, it’s labeled as “Electronic Throttle Control System Malfunction Power Management.”