This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
Definition
Code P2135 refers to the throttle sensor of all cars made after 1996. The system has detected an error with one of the sensors inside the throttle or pedal. This code reads as Throttle/Pedal Position Sensor/Switch A / B Voltage Correlation.
Meaning
Since 1996, all vehicles have wires that connect to each part of the drivetrain. In the case of code P2135, the readings from either the throttle or the pedal don’t match. The powertrain control module (PCM) is calibrated, so both sensors should deliver readouts that are close together. The more you press on the gas, the more the throttle opens up. If there is a significant disparity, the PCM will trigger this code. Since there can be minor differences between the sensors, code P2135 usually happens when the discrepancy is so substantial that the reading has to be inaccurate.
Causes
Because there are so many sensors and wires in modern cars, the common reason for this code is that one of these components is faulty. In rare cases, there might be a problem with the throttle control, but you will notice symptoms while driving. Overall, here are the top reasons why you may be seeing this code.
- Faulty PCM - The Powertrain Control Module’s sensors are misreading the throttle controls.
- Faulty Throttle Position Sensors - Even though the throttle is matching the pedal, the sensors are not indicating it.
- Faulty Accelerator Position Sensor - Rather than the problem lying in the throttle, the sensor monitoring the pedal might be inaccurate.
- Disruption in the Throttle Position Sensor - The connections going into the throttle sensor might be corroded, damaged, or too short (and popped out).
- Disruption in the Accelerator Position Sensor - The connections going to the pedal might be corroded or damaged or too short.
Symptoms
If the throttle and the gas pedal are not working harmoniously, it can create several noticeable problems. If the light comes on and you don’t detect any symptoms, then the likely culprit is a faulty sensor. Fortunately, issues with your car’s throttle are not ambiguous, so anyone can figure out that something is wrong.
Here’s what you can experience in that situation.
- Surging or Hesitation While Accelerating - The acceleration process should be smooth and match your foot’s position on the pedal.
- Engine Revving While Idling - Even if your foot isn’t on the gas, the throttle may be opening by itself.
- High RPMs - Typically, a car’s RPM gauge should be within 600 to 1000 while idling. It will go up while accelerating but should come back down quickly.
- Vehicle Stalling - When the throttle is opened too much, it can flood the engine and cause a stall. You may notice this while idling or accelerating.
- Check Engine Light Comes On
Diagnosis
You will likely have to take your car in to a mechanic to diagnose this problem correctly. Because the issue can be with either the throttle wiring or the accelerator, you need special devices to check both the voltage and ohms (resistance) of each sensor.
If you do have a multimeter, you’ll need to find where each sensor is within the car and test them individually. You will also need to know the correct rating for both voltage and resistance for that make and model.
Another way to determine the issue is to check any recalls for your vehicle. Sometimes, manufacturers will be able to detect throttle and accelerator problems on various makes and models. In this case, there should be a bulletin for your particular car.
Common mistakes
There are two throttle sensors, so be sure that you know which is which and that they go back into the correct position. Again, we recommend taking your vehicle to a professional for an accurate diagnosis.
Another mistake is not checking each sensor. Even if there is a problem with one of the sensors, the others may be faulty. Be thorough with your diagnosis, so everything gets fixed right the first time.
How serious is this?
Because the sensors control your throttle, this code can be potentially severe or life-threatening. While the sensors won’t cause you to accelerate with the brake applied, stalling out while driving can be hazardous. Also, when you are pressing the gas, the car may lurch forward faster than you expect, which can cause collisions.
What repairs can fix the code?
Once you identify the precise cause of the problem, you can either replace the sensor itself or the wiring. For example, if the issue was a corroded wire, the sensor itself should be okay. If both throttle sensors and accelerator sensors are in good shape and the wiring looks intact, then the likely culprit is the PCM.
Before replacing anything, however, we highly recommend resetting the code and driving the car again. This way, you can see if the check engine light comes on a second time. If it doesn’t, the issue may have been a fluke. As long as you don’t experience the noticeable symptoms, your vehicle should be okay.
Related codes
- Error Code P2136
- Error Code P2137
- Error Code P2138
- Error Code P2139
- Error Code P2140
Conclusion
Your car’s throttle system is critical, so you should repair this code immediately. However, if you don’t notice problems with acceleration or revving, we suggest resetting your OBD2 sensor to see if the light comes back on. A professional mechanic is better trained at diagnosing and replacing these sensors, so keep that in mind.
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