GarageGuideElectronic throttle (position sensor correlation)
P2135 Code: Throttle/Pedal Position Sensor A/B Voltage Correlation
P2135 stands for "Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation." Most modern cars use an electronic throttle: there is no cable from the gas pedal, and a motor opens the throttle. For safety, the throttle body has two position sensors that should always agree. P2135 means their readings no longer match.
When the two sensors disagree, the computer cannot be sure how far the throttle is open, so it protects you by limiting power, often called limp mode. That is why P2135 often shows up as a sudden loss of power. The cause is usually a worn sensor inside the throttle body or a wiring problem.
Sudden limp mode in traffic or while merging is a safety concern. The car may also stall. Get it diagnosed promptly, even if the problem comes and goes.
If the car is in limp mode, drive slowly to a safe place or shop, and avoid highways and merging, since power may be very limited. If the problem is intermittent, be ready for sudden power loss until it is fixed.
Symptoms you might notice
- Sudden loss of power or limp mode
- Engine barely responds when you press the gas
- Electronic throttle warning light (often a wrench or lightning bolt symbol)
- Stalling or rough idle
- Check engine light on
- Problem may come and go, especially over bumps
Common causes
Worn throttle position sensor
The sensors are usually built into the throttle body and wear with age. On many cars, the fix is a new throttle body assembly.
Damaged wiring or connector
Corroded pins, a loose connector, or chafed wires to the throttle body cause the sensor signals to drift apart.
Poor ground connection
A bad engine ground can affect sensor voltages and cause correlation errors.
Accelerator pedal sensor problem
On some vehicles the code also covers the pedal position sensors, so the pedal assembly can be involved.
Water in the connector
Moisture from washing the engine or a leak can get into the connector.
Engine computer fault (rare)
Rarely, the computer's sensor supply or input circuit fails.
Before you buy parts
P2135 means the throttle sensors disagree, not automatically that the throttle body is bad. Check the connector and wiring first, especially if the problem comes and goes. If the throttle body is replaced, look up whether your car needs a throttle relearn, or the new part may not work correctly.
What to check
- Inspect the throttle body connector for corrosion, bent pins, water, or a loose fit. Make sure it clicks firmly into place.
- With the engine off, follow the wiring from the throttle body for chafing or damage.
- Check the main engine ground straps for corrosion or looseness.
- Clear the code and see how quickly it returns. A code that returns over bumps points toward a wiring or connector problem.
- A shop can graph both sensor voltages as the throttle opens. Two smooth lines that drift apart point to a worn throttle body; sudden dropouts point to wiring.
Possible repairs
Repair the connector or wiring
Cleaning corroded pins or repairing damaged wires can fix P2135 without new parts.
Replace the throttle body
On most cars the sensors are built into the throttle body, so the assembly is replaced. Many cars then need a throttle relearn procedure.
Repair the engine ground
Cleaning and tightening a bad ground strap can restore correct sensor voltages.
Replace the accelerator pedal assembly
If testing shows the pedal sensors disagree, the pedal assembly is replaced.
Parts and tools that may help
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Frequently asked questions
What does P2135 mean?
It means the two throttle position sensors in the electronic throttle body disagree. The computer limits power for safety because it cannot be sure how far the throttle is open.
Can I drive with P2135?
Carefully, and avoid highways. The car may suddenly lose power or go into limp mode, which is risky in traffic.
Why does my car go into limp mode?
When the throttle sensors disagree, the computer limits power to prevent unintended acceleration. P2135 is one of the most common reasons.
Will cleaning the throttle body fix P2135?
Usually not. P2135 is about the sensors, not carbon buildup. Wiring repair or a new throttle body is the typical fix.
How much does it cost to fix P2135?
A connector or wiring repair can be inexpensive. A new throttle body costs more, though on many cars it is a manageable DIY job with a relearn.