You’re stopped at a stoplight, waiting for the light to turn green. Once the light changes, you suddenly notice that no matter how hard you step on the gas, engine power is significantly reduced.
After you limp the vehicle home, you plug in your diagnostic tool and it reads P2135. What does this code mean and why are you experiencing these problems?
Read on to find out.
What Does the P2135 Code Mean?
Diagnostic trouble code (DTC) P2135 stands for “Throttle/Pedal Position Sensor/ Switch A/B Voltage Correlation.” This code appears when your car’s primary computer, which is often referred to as the powertrain control module (PCM), detects a problem with one of throttle and/or the pedal position sensors/switches. In most cases, the ECM will also force the vehicle into Reduced Power Mode.
How Code P2135 is Set
On an Electronic Throttle Control (ETC) system, the PCM keeps track of throttle plate position and uses input from two or in rare cases, three throttle position (TP) sensors mounted on the throttle body and a pair of accelerator pedal position (APP) sensors connected to the accelerator pedal.
Think of this as “throttle by wire,” because there’s always an electronic module receiving input from the APP sensors, driving the motor that opens the throttle plate, and reading throttle plate position from the throttle position sensors.
Redundant sensors are used on the accelerator pedal AND the throttle body as a solidly dependable way of detecting faults by comparing the sensor inputs to each other in real time.
And remember, unlike the redundant circuits and hydraulics in military aircraft, these sensors don’t come in pairs, so one sensor will still work if the other one fails. If one sensor fails the algorithms in the PCM or module are written to prevent accidents due to uncontrolled throttle events.
If one sensor doesn’t work or doesn’t agree with the other sensor as it should, fail-safe mode kicks in, reducing or eliminating throttle response for safety purposes. In some cases, the vehicle will only idle or it might only provide half-throttle, and it will usually turn on a warning light. Fords use a light shaped like a wrench, but other vehicles may use an ETC warning light shaped like inverted parentheses with a lightning bolt between them.
What are the Possible Causes of the P2135 Code?
Error code P2135 can have a lot of potential causes. Below are just some of the possible issues that may have resulted in the P2135 code:
- Accelerator pedal position assembly failure
- TPS failure
- PCM issues (e.g., software is outdated)
- Circuit problems (e.g., damaged wires and poor connections)
What are the Common Symptoms of the P2135 Code?
You may notice one or more of the following symptoms when error code P2135 is set:
- Decreased engine performance
- Engine going into “limp home” (Reduced Power) mode
- Frequent stalling or sudden stopping
- Check engine light is on
How to Diagnose the P2135 Code
Some very crucial reminders below if you plan to diagnose the code yourself:
- Don’t ever open the throttle body with your fingers, even with the engine switched off or with the throttle body removed. On some vehicles, this can ruin the throttle body mechanism so that it has to be replaced. Always have an assistant hold the throttle pedal down to open the throttle plate.
- NEVER clean the throttle body with your fingers or put your fingers into the throttle body for ANY REASON. Always use a brush, because if the throttle body plate is driven closed (like if the assistant releases the pedal) the throttle body will seriously injure your fingers. Keep your fingers out of the throttle body at all times.
Because many issues can trigger the P2135 code, you may have a hard time pinpointing its exact cause. Use these detailed video references as a guide to help you diagnose the code properly:
How to Fix the P2135 Code
If you are not confident with your automotive know-how and DIY skills, let your mechanic take care of the issue. Otherwise, you may address the P2135 code yourself.
Identify what triggered the code, then figure out how to resolve it by doing your research on confirmed fixes that apply to your specific vehicle. You can also use these online auto repair resources and guides or get an ALLDATA subscription (for comprehensive factory repair information) in order to get more guidance.
Be sure to consult your owner’s manual before starting the repair process. What works for one vehicle might not work for another because different makes and models typically have their specific repair instructions. You don’t want to accidentally make the problem worse with an inappropriate fix.
When in doubt, contact your mechanic.
Other Notes About Code P2135
Other vehicle manufacturers will label this code differently, such as: “throttle position sensor circuit range/performance” on a Nissan Infiniti or “electronic throttle control system malfunction power management” on a Hyundai.
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