P2135 code: Mechanic advice to diagnose & fix

P2135 Code
Throttle/Pedal position Sensor/Switch A/B Voltage Correlation

Your Check Engine light is on, and your OBD2 scan tool tells you it’s thanks to code P2135.  Our mechanic shows you how to diagnose and fix a P2135 code.

What is code P2135 and what does it mean?

P2135 is a “Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation” diagnostic trouble code. In English, that means your car’s computer, the Powertrain Control Module (PCM), detects an issue with either one of the two throttle position (TP) sensors or the pedal position sensors

If your engine is weak, your car is having difficulty accelerating, it stalls out, or has entered limp mode (when the engine cuts off at low RPM), and you’ve got a P2135 check engine code, there’s a problem with your throttle body position sensors. Unfortunately, you’ll have trouble driving your car until it’s resolved and the code is cleared.

Watch this video for expert advice from our mechanics to help diagnose trouble code P2135:

Video: Check Engine Light? Reduced Engine Power or Stalling – Code P2135

What do the throttle position (TP) and pedal position sensors do? 

Throttle position (TP) sensors: 

The two TP sensors are connected to the throttle body, which is connected to your car’s engine intake system. 
 
The throttle blade is what allows air to enter the engine, and it opens wider when you step on the pedal to accelerate in order to let in more air. It’s the TP sensors’ job to monitor how much air is in the engine by letting the computer know how far open the throttle blade is. 

Pedal position sensors: 

The pedal or accelerator pedal position sensors monitor the amount of fuel that enters the engine in relation to how hard you press the gas pedal.

What triggers P2135?  

Under normal circumstances, the voltage data from each sensor pair should correlate—TP sensor 1 should be showing similar data to TP sensor 2, and the same goes for both pedal position sensors. If that data doesn’t correlate, and one sensor in a pair is sending different data to the computer from the other sensor, a P2135 code is triggered.

How serious is code P2135?: Is it OK to drive with P2135? 

P2135 can cause stalling out, so you should avoid driving with it.

What are typical P2135 code symptoms?

P2135 symptoms can include: 

  • Low engine power—your car may go into reduced power mode, which is known as “limp” or “limp-home” mode 
  • Difficulty accelerating, such as hesitation or surging when hitting the gas 
  • Stalling after stopping 
  • Engine revving when you aren’t pressing the gas 
  • Higher-than-normal revolutions per minute (RPM) 
  • Your throttle won’t change from the current RPM 
  • Your Check Engine light is on
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What are P2135 code causes and how can I diagnose them? 

P2135 code causes can include: 

  • TP or pedal position sensor issues or failure 
  • Throttle body issues 
  • Disconnected or corroded terminal connectors 
  • Faulty, damaged, or short wiring 
  • PCM issues 
  • Incorrect dielectric grease use

How to diagnose P2135 causes:

Scanning and graphing TP sensor data

With your car idling in Park, use an OBD2 scan tool to view the voltage output data from the two TP sensors. 

Select the following in order on your scan tool:

  • “TAC Data” (both the TP and pedal position sensors fall under the electronic throttle actuator, or TAC, system) 
  • “TP Sensor 1” 
  • “TP Sensor 2” 
  • “TP Sensors 1 and 2”

You’ll see that the values for sensor 1 and sensor 2 aren’t exactly the same, which is normal. What you’ll check for is whether the rate at which they increase correlates when you press the gas. 
 
The scan tool our mechanic used in the above video indicates an equal increase with “Agrees” (as in, the increase from sensor 1 agrees with that from sensor 2) and indicates an unequal increase with “Disagrees.” 
 
Keeping the car idling in Park, gradually step on the gas pedal and watch your scan tool to see whether the voltage outputs increase equally. 
 
If the increase isn’t equal, you can use your scan tool to graph the change in acceleration, which will show which sensor isn’t operating correctly. If the graph shows that one sensor has a noticeable spike or dip, you’ll know the code was triggered by that sensor.

Checking for disconnected or corroded connectors and damaged or short wires

Continue to graph and watch the data while you check out connections and wires under the hood. 
 
Wiggle the wires to see if the data from either sensor spikes or dips significantly. You could also have someone continue to step on the gas while you check under the hood. 

With the engine turned off, you can unplug the TP sensor connectors to check for any corrosion that could have triggered the code. 
 
If you don’t see anything that looks like an obvious issue, most likely, the code was triggered by the throttle position (TP) sensor or the pedal position sensor, because that is the most common cause of a P2135 code.

How do I fix code P2135?

If P2135 was triggered by a connection or wiring issue, depending on the issue, you may be able to replace it. 
 
While cleaning and keeping your throttle body clean won’t fix the issue and clear the P2135 code, keeping it clean is always a good idea. To clean the throttle body, use a brush and some throttle body cleaner.

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